Download Problem Weeds Guide - Millennium Reserve

Roots Neighborhood Habitat
Problem Weeds Guide
Illinois Department of Natural Resources
Coastal Management Program
Roots Neighborhood Habitat Problem Weeds Guide
Updated April 8, 2014
Introduction
This guide will introduce some basic botanical concepts that can help you identify and control weeds in a
garden setting. The guide starts with basic plant anatomy, and then discusses the four most commonly
used weed control methods. A section covering the weeds most commonly found in urban settings
contains illustrations, descriptive information, and the best control method for each plant.
A weed is a plant that grows where a person doesn’t want it to grow. In your wildflower garden, you’ll
use the word “weed” to describe any plant that you didn’t put into the ground. In a garden, weeds can
hoard water and nutrients and shade out your native plants, eventually taking over.
The good news is that most weeds do not compete well with native plants. Within 3 years, 90% of the
weeds in your garden should be under control, with a bit of diligence on your part.
There are nearly 1,000 plants in the Chicago area that one might call “weeds”. Most of them are
adapted to grow in low-nutrient, disturbed soils. In other words, most soil that you’d find in a city.
Many of these plants can grow in sidewalk cracks, which tells you just how adapted they are to living in
unforgiving places.
Most of these plants seldom become a problem and can be easily controlled. A few can become
invasive and will quickly take over a garden, much in the same way they will take over a natural area or a
farmer’s field. Knowing how to recognize these plants and control them is important.
There are three types of life cycles in plants, and the best control method for a weed will depend on its
life cycle.
Annuals are plants that sprout from seed and flower in a single growing season. Pulling and
cutting is the best way to control them.
Biennials are plants that grow a rosette or non-flowering stem in the first year, then flower in the
second year before dying. Spading is the best way to control them.
Perennials are plants that flower for multiple years with the roots surviving over winter. Because
of extensive root systems, perennials are the most problematic of garden weeds. Perennials vary
in their best control method, but frequently herbicide is the best way to control them.
Regardless of the type of plant, a weed should be removed before it sets seed. When a plant’s seeds
mature they typically fall to the ground near the parent plant. Some plants can produce over 10,000
seeds. By removing the seed source, the weed can eventually be controlled. Once a flower is pollinated
it can produce seed even if the plant is killed. Always dispose of flowering weeds in the trash instead of
with yard waste, so that the seeds are not spread elsewhere.
Plants are most vulnerable when getting ready to flower. Cutting, spading, or using a weed killing
herbicide is best done at these times.
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Roots Neighborhood Habitat Problem Weeds Guide
Updated April 8, 2014
Terminology
To effectively control weeds, it is helpful to know basics of plant anatomy. Terms that are good to know
are shown below.
Leaf: the parts of a plant where energy is produced. Most store-bought herbicides are absorbed into
the plant through the leaves.
Rhizome: an underground, horizontal stem that produces new above-ground growth away from the
parent plant.
Root: the part of the plant that anchors it to the ground, takes up water and nutrients from the soil, and
stores energy.
Taproot: a large root that smaller roots grow off of, for example, a carrot
Root Crown: the top part of the root, nearest the surface of the soil. Stems grow from the root crown.
Stem: the above-ground portion of the plant that provides support to branches, leaves and flowers.
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Roots Neighborhood Habitat Problem Weeds Guide
Updated April 8, 2014
Treatment Methods
There are four treatment methods that you can use to control nearly every weed you will encounter in
your garden. Cutting and pulling is effective on annuals and some perennials. Spading is effective on
biennials and some perennials. Herbicide is effective against perennials. When removing weed material
that is in flower, dispose of plants in trash bags instead of with yard waste. Pollinated flowers can
continue to produce seed even when removed from the ground, and compost piles do not get hot
enough to kill the seeds.
CUTTING
Cutting is an alternative to pulling that minimizes soil
disturbance. Pulling may also stimulate new growth if the
stem or root is broken. Cutting a stem weakens the plant
and makes it less likely new growth will be generated.
Cutting is best done with a garden shear. Plants should be
cut as close to the ground as possible. If plants are not in
flower, you can leave the cuttings on the ground as natural
compost.
SPADING
Spading is done mainly on biennial plants. The process
separates the root crown from the root, keeping new stems
from growing.
Spading can be done with a garden spade or hand spade.
The tip of the spade should be placed against the root,
slightly below the surface of the soil. Apply a downward
thrust at a 30-45 degree angle to cut through the root.
PULLING
Pulling can be used on weeds that have shallow root
systems or short taproots. When pulling, the important
thing to keep in mind is not to break the stem from the
root. Otherwise the plant may grow a new stem. Grasp the
stem near the root crown, where the stem is the strongest
and the force of pulling will be transferred to the root.
Pulling can be made easier with the help of a dandelion digger. These hand tools have a curved blade
with a prong at the end. They are designed to give extra leverage when pulling a plant out of the ground.
The tool is used by wedging the prong underneath the root crown, which is usually thicker than the
stem. Applying downward pressure on the handle lifts the pronged end, and the weed along with it.
Once loosened, the weed is much easier to pull from the ground.
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Roots Neighborhood Habitat Problem Weeds Guide
Updated April 8, 2014
Step 1: wedge the digger against the root, just Step 2: Press down on the handle of the digger to
underneath the top of the soil.
lift the plant up out of the soil.
HERBICIDE
For some perennial weeds, herbicide may be the best method of control. In most garden settings, an
herbicide called glyphosate is the safest to use. It is an herbicide that spreads throughout the tissue of
the plant. It can be purchased at most lawn and garden stores under various product names, Roundup
being the most well-known brand. These store-bought mixes are designed for spraying onto the leaves
of the target plant, and the area is safe for people to enter within an hour. Glyphosate breaks down
quickly in soils. Glyphosate is also a non-selective herbicide, meaning it will kill any plant that is sprayed.
Use care with this and any other herbicides to make sure you are not killing desirable plants. An
experienced lawn and garden supply store can offer more assistance if you find the need to use
herbicides.
Always follow label directions with herbicides to avoid using too much or exposing yourself to the
chemicals. Wear eye protection such as safety glasses, rubber gloves, a long-sleeved shirt and long
pants when working with herbicides.
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Roots Neighborhood Habitat Problem Weeds Guide
Updated April 8, 2014
How to Use This Guide
The plants in this guide represent weeds that are commonly seen in garden settings. They are arranged
by several leaf traits. Traits are listed in the following order:
1. Alternate, Opposite, Whorled
 Alternate: only one leaf grows from a point on the stem; appear spirally arranged
 Opposite: two leaves grow from a point on the stem, directly across from each other
 Whorled: three or more leaves grown from a point on the stem, spaced apart evenly
2. Simple or Compound
 Simple: each leaf has a single blade
 Compound: each leaf has multiple tiny blades called leaflets
3. Shape, from narrowest to widest
 Linear: grasslike
 Hastate: wined
 Oblong: outstretched
 Deltoid: triangular
 Lanceolate: lance-shaped
 Cordate: heart-shaped
 Ovate: teardrop-shaped
 Reniform: fan-shaped
 Elliptic: oval
 Orbicular: round
 Sagittate: arrowhead
Narrow
(Linear)
Oblong
(Oblong)
Lance-shaped
(Lanceolate)
Teardrop
(Ovate)
Oval
(Elliptic)
Arrowhead
(Sagittate)
Winged
(Hastate)
Triangular
(Deltoid)
Heart-shaped
(Cordate)
Fan-shaped
(Reniform)
Round
(Orbicular)
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Roots Neighborhood Habitat Problem Weeds Guide
Updated April 8, 2014
The leaf traits covered on a particular page appear at the top of each page.
If you have a plant you suspect to be a weed:
1. Note the three traits mentioned on the previous page.
2. Take a photograph of the leaf. Putting the leave against a solid-color background will help bring
out details.
3. Use the keywords at the top of the page to match the leaf/plant to the description.
4. Check the native plant guide as well to eliminate possible native lookalikes.
5. If you still are not sure, check with a University of Illinois Extension office, or refer to online
weed resources.
Each plant description has the common name and the scientific name for each plant. Sometimes the
scientific name will have the abbreviation “sp.” This means there are several closely related species
with similar traits that can be controlled in the same way. The guide also ranks the level of weediness
for each species:



Low: plant is not likely to take over a garden and can be easily controlled.
Medium: plants can be controlled but it will take some time, possibly more than a year
High: plants can quickly take over a garden if not removed. Control can take multiple years.
Some plants are marked as “noxious weeds.” Noxious weeds must, by law, be controlled by the
property own if found on their property. Those labeled “invasive” have the ability to quickly
overrun an area and crowd out all other vegetation.
The best control methods for each plant are listed, along with several distinguishing traits that should
make identification of a plant easier.
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Alternate
Simple
Linear, Oblong
Yarrow (Achillea millefolium) – perennial
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-white flowers
-feathery leaves, 3-10” long
-sage-like scent when crushed
A perennial weed that spreads via rhizomes. This plant has feathery
leaves and small, white, 5-petal flowers. When not in bloom, the plant
produces a number of leaves in a cluster low to the ground. Crushed
leaves smell like sage.
Yarrow can be easily controlled with repeated cutting. Plants can be
pulled if growing in open ground. Rhizomes break easily and may
generate new growth.
Canada Thistle (Cirsium arvense) - perennial
Weediness: high, NOXIOUS WEED
Control Method: herbicide
Distinguishing Traits:
-pale pink flowers smaller than other thistles
-short spines on leaves
-no spines on the stems
A weedy perennial thistle that can invade gardens and lawns as easily as
vacant lots. Produces branching stems that can flower any time of the
year. Other weedy thistles have spiny stems; Canada thistle does not.
The leaves are a light green color underneath that sometimes appears
ashen.
Because of a dense, deep root system, herbicide is the best control
method. Cutting will set the plant back but not eliminate it.
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Alternate
Simple
Oblong
Nodding Thistle (Carduus nutans) - biennial
Weediness: low
Control Method: spading
Distinguishing Traits:
-magenta flowers
-flower head droops down
-long spines on leaves and stems
The leaves, stem, and flower head of this biennial thistle are covered
with long, sharp spines. It produces a whorl of deeply cut spiny leaves,
up to 2 feet in diameter, in the first year of growth.
A biennial with a large taproot, first and second-year plants can usually
be killed by spading.
Bull Thistle (Cirsium vulgare) - biennial
Weediness: low
Control Method: spading
Distinguishing Traits:
-magenta flowers
-flower head held straight up
-long spines on hairy leaves and stems
This biennial thistle is spiny all over: leaves, stems, and flower head.
Leaves and stems are also hairy. A biennial, it produces a whorl of
deeply cut spiny leaves in the first year of growth. The whorl stays
green through winter and can reach 3 feet across.
A biennial with a large taproot, first and second-year plants can usually
be killed by spading.
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Alternate
Simple
Oblong
Curly Dock (Rumex crispus) - perennial
Weediness: low
Control Method: spading, pulling
Distinguishing Traits:
- curled leaves that resemble cooked bacon
-diminutive yellow-green flowers
-stems and flowers turn rich brown when they mature
This perennial weed produces a whorl of wavy-edged leaves in the
spring. In summer, it sends up a flowering stem with clasping,
spirally arranged leaves. The small, yellow-green flowers turn a
distinctive rust color as seeds ripen
This perennial has a large taproot and can be controlled by spading
or pulling with the help of a dandelion digger. There are several
Rumex plants that get weedy. All have similar leaves and the same
yellow-green flowers.
Siberian Elm (Ulmus pumila) - perennial
Weediness: moderate
Control Method: pulling
Distinguishing Traits:
-numerous alternate leaves on gray branches
-leaves greenish-gray underneath
-disk-shaped winged seeds
A parkway tree whose seeds often blow into gardens and germinate in
open soil. The leafy ash-gray woody stems of seedlings are distinct.
The sawtooth-edged leaves are a grayish green underneath, between
1-2 inches long.
Plants should be pulled using a dandelion digger as soon as they are
found. Seedlings left for 3-6 months are difficult to pull because of
rapid root growth. Cutting is ineffective, stimulating growth of
multiple stems. Winged seeds germinate quickly and should be
removed from a garden if they land.
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Alternate
Simple
Lanceolate
Mustards (Brassica sp.) - biennial
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-irregularly lobed leaves
-4-petal white or yellow flowers
-long upright seed pods
Several members of the mustard family grow as garden weeds. All
are biennial plants that in the 1st year produce rosettes of long
leaves with erratic lobes that resemble radish or mustard greens.
Leaves on flowering stems are sparse with fewer lobes. All
mustards have 4-petaled, cross-like flowers that are either yellow or
white.
Black Mustard
(Brassica nigra)
Mustards have shallow taproots and are easily pulled. Pods split
when ripe and spread seed several feet away from the plant.
Plants with seed pods should be discarded with trash instead of
yard waste/compost.
Asiatic Dayflower (Commelina communis) - perennial
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-waxy leaves 1-4 inches long
-2-petaled purple flowers
-forms colonies
The dayflower has distinct purple flowers with two petals. Flowers
only last a day before closing. It spreads via rhizomes and quickly
forms colonies in areas of open soils. Leaves have a waxy texture
and a swollen joint where they clasp the stem.
The plant is weakened by cutting and can be eliminated if re-sprouts
are quickly cut. Roots are shallow and the plant can be pulled if it is
growing by itself in open ground.
10
Alternate
Simple
Lanceolate
Horseweed (Conzya canadensis) - annual
Weediness: low
Control Method: pulling, cutting
Distinguishing Traits:
-very tall (up to 6 feet)
-densely spiraled lance-like leaves
-white flowers that partially open
Horseweed is a native wildflower fond of barren soil and open ground.
It sprouts in late spring and grows quickly. The numerous lance-shaped
leaves are arranged spirally on the stem. The small white flowers
appear late summer, and never fully open.
Horseweed has shallow roots and can be pulled with little soil
disturbance. Cut stems may resprout, but the new growth seldom gets
tall. The plant produces thousands of seeds that usually fall near the
parent plant. It can quickly colonize the open ground of a garden.
Tall Goldenrods (Solidago altissima, S. canadensis) - perennial
Weediness: medium
Control Method: cutting, herbicide
Distinguishing Traits:
-feathery plume of small yellow flowers
-leaves with prominent saw-toothed margins
-stems often form galls (see description below)
Tall goldenrods are native perennial wildflowers that produce 3-5 foot
stems of spirally-arranged leaves, 1-4 inches long. The leaves have a
saw-toothed edge. Showy plumes of yellow flowers bloom in early fall.
The plants spread via rhizomes and form large colonies. Plants often
develop ball-like galls along the stem from the larvae of harmless gall
wasps.
Tall goldenrods look similar to horseweed but as perennials can be
harder to control. A plant can form a large colony in several years. Tall
goldenrods do not take well to being cut. Plants cut twice a year (in July
and again before flowering) typically die out after 2-3 years.
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Alternate
Simple
Lanceolate
Dame’s Rocket (Hesperis matronalis) - biennial
Weediness: medium, INVASIVE
Control Method: spading, cutting, pulling
Distinguishing Traits:
-purple or pink 4-petaled flowers
-stems dense with spirally-arranged leaves
-1st year rosette stays green over winter
Dame’s rocket produces a rosette of numerous lance-shaped leaves in
its 1st year. In spring of the 2nd year, it produces a 2-3 foot stem. The
2nd year leaves are more pointed than the 1st year rosette leaves. The
purple or pink flowers resemble garden phlox, but have 4 petals instead
of 5.
The 1st year rosettes can be spaded or pulled with a dandelion digger.
The 2nd year plants can be spaded, cut, or pulled. Cutting is best done
before the flowers open. Seeds can be scattered up to 15 feet from the
parent plant, helping this plant to quickly take over open areas.
Evening Primrose (Oenothera biennis) - biennial
Weediness: low
Control Method: spading, pulling, cutting
Distinguishing Traits:
-yellow 4-petaled flowers that open at night
-numerous spirally arranged leaves
Evening primrose produces a dense rosette of lance-shaped, light
green leaves in the 1st year. These leaves are usually toothed and
often have a reddish midvein. The 2nd year plant produces a 3-5 foot
flowering stem with numerous 4-petaled yellow flowers. Both
flowers and leaves are spirally arranged on the stem.
Evening primrose is a native wildflower adapted to disturbed areas.
Spading will usually kill the plant. Evening primrose has an 8-12 inch
taproot; cutting often triggers resprouting. If pulling, use a dandelion
digger.
12
Alternate
Simple
Lanceolate
Mullein (Verbascum thapsus) - biennial
Weediness: low
Control Method: pulling, spading
Distinguishing Traits:
-light green leaves covered with soft, dense hairs
-tightly-packed spike of 5-petaled yellow flowers
No other weedy plant resembles mullein. The furry light green leaves
resemble a lamb’s ear. The first year rosette can grow as large as 3
feet across. In the second year, a single flower spike with hundreds of
pale yellow flowers grows up to 7 feet tall.
Mullein is easily controlled in a garden. Plants have a shallow fibrous
root system. Pull 1st year plants with a dandelion digger. Spade 2nd
year plants when the flowering stem starts to grow.
Chicory (Cichorium intybus) - perennial
Weediness: medium
Control Method: cutting, herbicide
Distinguishing Traits:
-dandelion-like basal leaves
-shrubby stems with tiny leaves
-lavender-blue flowers
Chicory has deeply cut leaves near the base of the stem that look like
dandelion leaves. Closer to the top, the stem-clasping leaves become
short and stubby. Stems are tough and woody with bristly hairs. The
blue flowers appear in summer and blooming may persist into fall.
Chicory is a perennial that seldom invades gardens but is tough to get
rid of once established. The dense root system makes it hard to pull.
Repeated cuttings eventually set it back. Herbicide applied to the
basal leaves early in the year is effective.
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Alternate
Simple
Ovate
Lamb’s Quarters (Chenopodium album) - annual
Weediness: low
Control Method: pulling, cutting
Distinguishing Traits:
-light green, toothed leaves
-tiny dull white flowers
Lamb’s quarters is the most common of several Chenopodum that
grow as garden weeds. All have light green toothed leaves and tiny
white flowers. Leaves get narrower towards the top of the plant. The
dull white flowers are surrounded by protective leaves that give them
a greenish appearance.
These annual weeds have shallow root systems and are easily pulled.
Cutting is also an effective control method.
Pokeweed (Phytolacca americana) - perennial
Weediness: low
Control Method: cutting, herbicide
Distinguishing Traits:
-Knob-like white flowers and berries
-broad oval leaves
-tall (up to 7 foot) hollow stems
Pokeweed is a native perennial wildflower that invades slightly
shaded areas.
The broad teardrop-shaped leaves somewhat
resemble a milkweed, though they are arranged spirally on the stem
instead of opposite. The white, knob-like flowers appear in summer
and ripen into deep blue berries. The flowering stem is often reddish.
Pokeweeds have large taproots that can grow to the size of a softball.
Pulling is difficult. Plants can be controlled by cutting, but will persist
for several years. Herbicide applied to the re-sprouts that appear
after cutting is highly effective.
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Alternate
Simple
Ovate
Climbing Nightshade (Solanum dulcamara) - perennial
Weediness: low
Control Method: cutting, pulling, herbicide
Distinguishing Traits:
-vine with woody stems
-bright purple and yellow flowers
-leaves with lobes at 90o angles
Climbing nightshade invades gardens, shaded ground and hedges.
The poisonous plant has a woody stem with light brown bark. Older
leaves have lobes set at 90o angles. The purple flowers resemble
those of a tomato, a close relative. Red berries quickly ripen to a
deep purple.
Climbing nightshade has brittle roots. Cutting is effective, but may
need to be done several times a year to kill the plant. If plants are
pulled, use a dandelion digger to keep the root from breaking.
Herbicide applied to re-sprouting foliage is highly effective.
Black Nightshade (Solanum nigrum) - annual
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-shiny pointed leaves similar to tomato leaves
-tiny white flowers
-small purple berries
This common, poisonous weed looks like a small tomato, a plant to
which it is closely related. Seldom more than 1 foot tall, the shiny
pointed leaves are often covered in holes from insect browsing. The
plants bloom in summer and produce dark purple berries in early fall.
Black nightshade is easily controlled by pulling. The roots are weak
and shallow and pull with little soil disturbance. Cutting also
eliminates the plant.
15
Alternate
Simple
Ovate
Horsenettle (Solanum carolinense) - annual
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-crooked stem
-deeply-lobed leaves
-white tomato-like flowers
Horsenettle is a relative of the tomato family that occasionally
invades gardens from vacant areas. It has a crooked, hairy stem
similar to a tomato vine. The deeply-lobed leaves are distinct. The
white flowers ripen into yellowish berries in the fall.
Horsenettle is easily controlled by pulling. The roots are weak and
shallow and pull with little soil disturbance. Cutting also eliminates
the plant.
Mercury (Acalypha sp.) - annual
Weediness: low
Control Method: pulling, cutting
Distinguishing Traits:
-tiny green flowers up and down the stem
-sticky stems, leaves and seeds
There are several species of native wildflowers called mercury that
grow as garden weeds. Seldom more than 1 foot tall, plants have
lance or oval-shaped leaves with saw-tooth edges. The tiny green
flowers grow from the same points as the leaves, and are wrapped
around the stem. All parts of the plant are covered in fine hairs that
stick like Velcro.
All mercury plants have shallow roots and can be pulled without soil
disturbance. They can also be cut.
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Alternate
Simple
Ovate, Sagittate
Purselane (Portulaca oleracea) - annual
Weediness: low
Control Method: pulling, cutting
Distinguishing Traits:
-mat-like growth
-fleshy leaves
-small yellow flowers
This mat-forming weed is common in open ground. The fleshy,
almost succulent leaves are alternating on the stem. The small
yellow flowers grow along stems and bloom throughout
summer.
Purselane roots are shallow and can be easily pulled. They
can’t compete with tall plants and get crowded out as gardens
get established.
Field Bindweed (Convulvulus arvensis) - perennial
Weediness: high, NOXIOUS WEED
Control Method: herbicide, cutting
Distinguishing Traits:
-twining vine
-arrowhead-like leaves
-white or pink bell-shaped flowers
Bindweed is a twining vine that wraps itself around anything it comes
in contact with. Stems emerge in spring and grow as much as an inch
a day. It also spreads via underground rhizomes and deep roots. The
white, bell-shaped flowers appear in early summer. The arrowheadshaped leaves are distinctive.
Bindweed is one of the most difficult weeds to control once
established. Repeated cutting will weaken the plant and take 3-5
years to kill it. Herbicide is highly effective on plants that are not
climbing up desirable vegetation. DO NOT PULL! Rhizomes are brittle
and break easily, resulting in multiple stem re-sprouts.
17
Alternate
Simple
Cordate
Morning Glory (Ipomoea sp.) - annual
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-twining vine
-heart or ivy-shaped leaves
-pink (sometimes purple or white) flowers
Morning glory is a twining vine that wraps itself around anything it
comes in contact with. Leaves are usually heart-shaped or ivyshaped. The large trumpet-shaped flowers are usually pink, but can
range from purple to white.
Morning glory is an easily-controlled annual. Most have bulbous
taproots and cutting is the best control method. Pulling with the aid
of a dandelion digger is also effective. Pull vines early in the year
before they have a chance to strangle desirable plants.
Velvet Leaf (Abutilon theophrasti) - annual
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-velvety heart-shaped leaves
-yellow flowers hidden behind leaves
No other plant, native or weed, has leaves with the texture that give
velvet leaf its name. It is usually found growing in open ground, and
is usually seen in recently established gardens. Flowers are often
hidden behind the large leaves.
Velvet leaf can be easily controlled by cutting. An annual with a
weak root system, it seldom re-sprouts.
18
Alternate
Simple
Cordate
Garlic Mustard (Alliaria petiolata) - biennial
Weediness: high, INVASIVE
Control Method: pulling
Distinguishing Traits:
-heart-shaped leaves with blunt-tooth margins
-garlic-like scent when crushed
-small white 4-petaled flowers
Garlic mustard is a biennial weed that will appear in shaded gardens
and along hedges. A dense rosette of rounded heart-shaped leaves
grow in the 1st year, staying green over winter. A flowering stalk
with pointed heart-shaped leaves grows in the 2nd year, with a spike
of small white flowers. Garlic mustard flowers in mid-spring.
Garlic mustard is highly invasive in wooded areas. If found in a
garden setting it should be immediately controlled. The roots are
shallow and the plant can be pulled. Seeds scatter up to 15 feet
from the parent plant. Any plants in flower or with seed pods should
be disposed of with trash.
Japanese Knotweed (Polygonum cuspidatum) - perennial
Weediness: high, INVASIVE
Control Method: herbicide
Distinguishing Traits:
-heart or triangle-shaped leaves with squared bases
-tall stems with red blotches
-spikes of tiny white flowers
Japanese knotweed forms large colonies with stems exceeding 10
feet tall. Stems are hollow with red blotches. The heart-shaped
leaves have blunt bases. The small white flowers appear in midsummer on upright spikes along the length of stems.
Japanese knotweed is highly invasive. Root systems are extensive
and deep and can damage building foundations. To control, spray
plants with an herbicide early in the year when still low to the
ground. Cutting taller stems and spraying re-sprouting stems is also
effective. Even with herbicide it can take 3-4 years to kill a single
plant.
19
Alternate
Simple
Deltoid
Flower-of-an-hour (Hibiscus trionum) - annual
Weediness: low
Control Method: pulling, cutting
Distinguishing Traits:
-lobed leaves with blunt-toothed margins
-white flower with purple accents
Rose mallow is a fast-growing summer annual. The triangular, lobed
leaves with round-toothed margins are unique amongst garden
weeds. The white flowers with purple accents stay open for less than
a day.
Rose mallow has a short taproot and can easily be pulled. Cutting is
also effective; plants seldom re-sprout.
“Grass” Clovers (Trifolium sp.) - perennial
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-typical 3-parted clover leaf with oblong leaflets
-short spike of pink, white, or yellow flowers
-leaflets often have a v-shaped “watermark”
“Grass” clovers were originally mixed in with lawn seeds and are now
common in gardens. They grow in low clumps, usually 1 foot tall or
less. Leaves are the typical 3-parted clover leaves. Most species
have a v-shaped “watermark” on leaflets. The small, ball-like spike of
flowers appears in early-to-mid summer.
Grass clovers are easily controlled by cutting. The fibrous roots are
shallow but spreading; pulling may disturb soil. Clovers compete
poorly against taller vegetation, but their ability to fix nitrogen to the
soil helps other weeds invade open ground.
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Alternate
Compound
Oblong
Sweet Clover (Melilotus officinalis., M. albus) - biennial
Weediness: high, INVASIVE
Control Method: cutting, pulling
Distinguishing Traits:
-tall, branching, woody stem
-spikes of small, white or yellow flowers
Sweet clover is a biennial that puts up stems in both years of growth.
First year plants are low-growing, usually 6-12 inches tall. Second
year plants can exceed 6 feet and are branching. Two species of
sweet clover occur as weeds: one with white flowers, the other with
yellow flowers. The plants otherwise look identical. Both bloom in
early summer.
Sweet clovers are invasive in natural areas but seldom more than a
nuisance weed in gardens. Do not allow sweet clover to set seed.
Seeds can survive over 30 years in the soil.
Crown Vetch (Securigera varia) - perennial
Weediness: high, INVASIVE
Control Method: herbicide
Distinguishing Traits:
-short, bushy growth
-compound leaves with 11-25 leaflets
-large ball of pink flowers
Crown vetch is a spreading, bushy clover. Seldom more than 2 feet
tall, plants can form a shrub-like cluster up to 6 feet in diameter. The
dark green leaves have 11-25 leaflets. A cotton ball-sized cluster of
pink flowers appears in early summer.
Crown vetch is highly invasive in natural areas. It often invades
gardens from alleyways and roadsides. Its extensive root system
helps it out-compete other vegetation and it resists pulling and
cutting. Seedlings and young plants can be pulled. Established plants
are resistant to cutting and pulling and are best controlled with
herbicide.
21
Alternate
Compound
Oblong
Sulfur Cinquefoil (Potentilla recta) - perennial
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-5 or 7-part palm-like leaves
-yellow flowers with 5 heart-shaped petals
-hairy leaves and stems
Sulfur cinquefoil grows as a branching, shrubby weed. It produces
compound basal leaves, usually with seven oblong lobes with
sawtooth margins. Leaves on the hairy stem are usually 5-parted.
The yellow flowers with heart-shaped petals bloom through summer.
Sulfur cinquefoil can be controlled by cutting. Several cuttings in a
growing season are sufficient. Young plants can be pulled. Older
plants have an extensive, woody root system and should be cut
rather than pulled.
Queen Anne’s Lace (Daucus carota) - biennial
Weediness: low
Control Method: spading, pulling
Distinguishing Traits:
-lacy leaves
-cluster of white flowers with 1 purple flower in the center
Queen Anne’s lace is the wild version of the carrot. Plants produce a
dense rosette of lacy, deeply divided leaves in the 1st year. The 2nd
year plants produce a branched stem with only a few leaves. Blooms
appear on an umbrella-like cluster of small white flowers, usually
with 1 purple flower in the center.
Like a carrot, Queen Anne’s lace has a long taproot. Spading will
usually kill a plant. Rosettes and flowering plants can be pulled with
a dandelion digger. Plants broken above the ground will resprout.
22
Opposite
Simple
Oblong, Lanceolate
Black Medic (Medicago lupulina) - annual
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-clover-like 3-parted leaf
-small balls of tiny yellow flowers
Black medic looks similar to clovers, though it grows taller, up to 2
feet. The 3-parted clover-like leaves are arranged spirally on the
stem. In summer, the plant produces a spike of tiny yellow flowers
that look like puffballs.
Black medic is related to alfalfa. It long ago escaped hay fields and is
now a common weed. Cutting is an effective control. Pulling small
plants, before the fibrous roots spread, is also effective.
Wood Sorrel (Oxalis stricta) - perennial
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-clover-like leaf with heart-shaped leaflets
-5-petaled yellow flowers
Wood sorrel is sometimes confused with clover. Sorrel leaves have
heart-shaped leaflets in 3-parts, where clover has round or oblong
leaflets. The plants are short, seldom more than a foot tall.
A native wildflower, wood sorrel can get weedy in the open spaces of
a garden. Cutting usually eliminates it after 2-3 cuts in a year. It does
not compete well against taller vegetation. If managed, it can serve
as a groundcover for a year or two while more desirable plants grow
to fill in open spaces.
23
Opposite
Simple
Ovate
Matted Spurges (Chamaesyce sp.) - annual
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-mat-forming
-oblong leaves opposite on stem
-white sap when broken
Matted spurge stems grow along the ground. A single plant can
produce up to 20 stems. The small (1/4 inch or less) leaves grow
opposite from each other along each stem. Tiny white flowers about
the size of a pinhead grow from the tips of the stems.
Matted spurges have weak roots and can be either cut or pulled to
control. Taller vegetation shades them out, so it rarely persists in
gardens.
Ragweed (Ambrosia artemisifolia, A. psilostachya) - annual/perennial
Weediness: low
Control Method: cutting
Distinguishing Traits:
-deeply lobed leaves
-leaves opposite on main stem, alternate on flowering stems
-small green ball-like flowers
Ragweed is easy to spot in a garden. The leaves tend to be teardropshaped with deep lobes. The leaves on the main stem are opposite.
On the flowering stems, the leaves are arranged spirally. Floral spikes
appear on the tips of branches and are a greenish-white color.
Two species of ragweeds will grow in gardens. The annual common
ragweed (A. artemisifolia) is usually encountered. Western ragweed
(A. psilostachya) is a perennial that forms small colonies by sending
out rhizomes from the main stem. Cutting is highly effective against
both.
24
Opposite
Simple
Sagittate
Giant Ragweed (Ambrosia artemisifolia) - annual
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-ivy-like leaves with saw-toothed edges
-leaves are opposite on main stem, alternate on flowering stems
-small green ball-like flowers
True to its name, giant ragweed can grow more than 10 feet tall. The
oval-shaped leaves develop deep lobes, making them resemble ivy
leaves. The leaves are silver-gray underneath. In late summer it
produces long spikes of yellow-green flowers.
Giant ragweed is seldom found in backyard gardens, but will invade
gardens in open areas. Small plants can be pulled. Larger plants,
more than 3 feet tall, should be cut.
Cutleaf Teasel (Dipsacus laciniatus) - biennial
Weediness: high, INVASIVE
Control Method: herbicide, spading
Distinguishing Traits:
-lettuce-like leaves with netted veins
-spines surrounding egg-shaped flower spike
-leaves clasp stem to form cups
Cutleaf teasel is a biennial, producing a rosette of irregularly lobed
saw-toothed leaves in the 1st year. The 2nd year stem has similar
leaves that clasp the stem and form a cup that traps water. The
flower heads are egg-shaped, surrounded by spike-like projections,
and producing small white (sometimes pink) flowers.
Teasels are highly invasive and should be removed immediately if
found. Spraying herbicide on 1st year rosettes is the most effective
control. Spading will weaken the plant but not kill it.
25
Opposite
Simple
Sagittate
Black Swallow-wort (Cynachum louiseae) - perennial
Weediness: high, INVASIVE
Control Method: herbicide, cutting
Distinguishing Traits:
-oval-shaped opposite leaves
-twirling vine
-pungent smelling dark purple flowers
Black swallow-wort is a branching, twirling vine that can grow 6 feet
long. The teardrop-shaped leaves with pointed tips are arranged
opposite on the stem. At the tips of branches, dark red-purple
flowers bloom in summer. The flowers have a smell that mimics
rotting fruit.
This plant is a persistent pest. A perennial, it produces a deep,
extensive root system making it difficult to control. Herbicide plants
in late spring before they climb desirable vegetation. Cutting stems
and putting herbicide on re-sprouting leaves is effective. It can take
several years to eradicate this plant.
Spearmint (Mentha spicata) - perennial
Weediness: low
Control Method: cutting
Distinguishing Traits:
-minty scent when crushed
-small pink flowers on thimble-like spikes
-square stems
Spearmint is the most common of several mints that become weedy.
It has a square stem with opposite, teardrop-shaped leaves with a
toothed margin. The crisscrossing veins give the leaf a net-like
appearance. Thimble-like spikes of light pink flowers are born at the
top of the plant.
Spearmint becomes bushy if left alone. Along with most weedy
mints, it can be killed by several cuttings throughout a growing
season. Younger plants can be pulled.
26
Opposite
Simple
Sagittate
Mouse-eared Chickweed (Stellaria media) - annual
Weediness: low
Control Method: cutting
Distinguishing Traits:
-small, ovate opposite leaves
-stems that flop towards the ground
-small white flowers with divided petals
Chickweed is a low-grown weed of lawns and gardens. The tiny, oval
leaves give the plant its name. Plants form a circular clump of dense
stems in late winter. The petals of the small white flowers are
divided down the middle, making it look like the flower has 10 petals
instead of 5. They bloom in spring.
Chickweed becomes weedy in open areas. In gardens it is easily
controlled by cutting or pulling. Chickweed competes well with taller
vegetation and should not be left to set seed.
Catnip (Nepeta cataria) - perennial
Weediness: low
Control Method: cutting
Distinguishing Traits:
-sawtoothed triangular leaves
-square stems
-earthy scent when crushed
Catnip is easy to ID in a garden because of its distinct, earthy-mint
scent. It has a square stem with opposite, triangular, saw-tooth
margined leaves. The leaf veins form a net-like appearance. The
small lavender-pink flowers emerge from along the tips of stems.
Catnip becomes bushy if left alone. Like most weedy mints, it can be
controlled by several cuttings throughout a growing season. Younger
plants can be pulled before the spreading root system is well
established. Catnip may attract outdoor cats, which will damage
other garden plants by trampling.
27
Alternate, Whorled
Simple
Lanceolate
Creeping Charlie (Glechoma hederacea) - perennial
Weediness: medium
Control Method: herbicide, cutting, pulling
Distinguishing Traits:
-rounded leaves with toothed margins
-spreading rhizomes form a thick mat
-small pink flowers on low stems
Creeping Charlie is a groundcover that escapes gardens and invades
open areas. Rhizomes grow roots and leafy stems. The rounded
leaves are opposite each other on the square stems. Though a mint,
the leaves do not have a scent when crushed.
Creeping Charlie will colonize any patch of open ground it is
introduced to. Herbicide is the most effective means of control.
Cutting and pulling are not always effective, as any broken root or
rhizome produces new growth.
Maples (Acer sp.) - perennial
Weediness: moderate
Control Method: cutting, pulling, herbicide
Distinguishing Traits:
-rounded or triangular lobed leaves opposite on the stems
-“helicopter” seeds
Maple seeds will sprout on nearly any type of moist ground.
Seedlings quickly develop an extensive root system. The lobes on the
leaves (usually 5) taper to a point. Seedlings can grow more than two
feet in a single year.
Maples are problems when their single-winged “helicopter” seeds
blow into gardens where they quickly sprout. The best control is to
remove seeds when they drop, usually mid-summer. Seedlings
should be pulled with a dandelion digger, as roots grow quickly.
28
Alternate, Whorled
Simple
Lanceolate
Sow Thistles (Sonchus sp.) – annual/perennial
Weediness: medium
Control Method: cutting, pulling
Distinguishing Traits:
-thistle-like leaves that clasp stem
-dandelion-like flowers
The several species of sow thistles all have thistle-like leaves that
clasp the stem. The tips of the stems branch, with each branch
producing several yellow flowers that resemble a dandelion. Sow
thistles tend to bloom in the mid-summer.
Whether annual or perennial, sow thistles can be controlled by
cutting; even perennial sow thistles are unlikely to resprout. The
numerous seeds produced by the flowers are moved around by wind,
allowing a single plant to quickly colonize open ground. Pulling
established plants, with long rhizomes, may disturb soil.
Dandelion (Taraxacum officinale) –perennial
Weediness: medium
Control Method: spading, herbicide
Distinguishing Traits:
-non-spiny thistle-like leaves
-yellow flower resemble a sunburst
Dandelions are one of our most common and well-known weeds.
Usually growing in the spring, they produce a rosette of deeply lobed
leaves that look like they have arrowheads on the tips. Several
stems, each with a yellow sunburst flower, emerge in late spring.
Dandelions produce a lot of seeds. Do not let them establish in a
garden. Pulling should be avoided as the long taproots break easily
and then grow a new plant. Spading is sometimes effective if done
several times over the growing season. Herbicide is the best way to
remove this plant from a garden setting.
29
Alternate, Whorled
Simple
Lanceolate
English Plantain (Plantago lanceolata) - perennial
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-Rosette of lance-like leaves with well-spaced teeth
-spikes of tiny white flowers
English plantain is a common sidewalk and garden weed, preferring
open ground with little competition. The waxy, lance-shaped leaves
have the occasional tooth along the margins. The leaves display
prominent parallel veins. The tiny white flowers appear in summer,
growing from a club-like flower head.
English plantain is seldom a problem in gardens. Plants are easily
controlled by cutting. Pulling is effective if no good plants will be
disturbed by the upturning of soil. A dandelion digger should be used
as leaves and stems break easily.
Hawkweeds (Hieracium sp.) - perennial
Weediness: low
Control Method: cutting
Distinguishing Traits:
-hairy, lance-shaped leaves
-cluster of small dandelion-like flowers on tip of long stem
Several species of hawkweeds can get weedy in gardens. They
produce either a whorl of leaves or have spirally arranged leaves low
on the stem. Leaves and stems are always hairy. A long stem with a
cluster of dandelion-like yellow or red flowers appears in
midsummer.
Hawkweeds are common in vacant and untended lots and seeds can
blow into gardens. Their fibrous roots compete with surrounding
plants. Cutting the plants several times in a growing season generally
kills it.
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Alternate, Whorled
Simple
Lanceolate
Common Plantain (Plantago major) - perennial
Weediness: low
Control Method: cutting, pulling
Distinguishing Traits:
-broad oval leaves with prominent veins
-long spike of tiny white flowers
Common plantain is often found in gardens and other open spaces.
The waxy, oval leaves have prominent parallel veins and wavy
margins. A long spike of tiny white flowers appears in early summer.
Plantains are seldom a problem in gardens. Plants are easily
controlled by cutting. Pulling is effective if no desired plants will be
disturbed by the upturning of soil by fibrous roots. A dandelion
digger should be used as the stems and leaves break easily.
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Printed by authority of the State of Illinois
May 5, 2014