Download Starting and Growing Beautiful Summer Bulbs

Garden Expo 2013
Starting and Growing Beautiful Summer Bulbs
— Susan Mahr, UW-Madison Department of Horticulture
Summer bulbs provide another dimension to gardening.
They add beauty and interest
to the landscape and, since
most of them are tender, they
offer a unique challenge to the
gardener. The flowering types
offer brilliant color, while those
grown primarily for their foliage
provide color and texture which
many summer annuals do not .
Some of the more commonly planted summer bulbs
that are considered here include caladium, calla, canna,
dahlias, elephant ears, gladiola
and tuberous begonia.
Why Plant Summer Bulbs?
Summer bulbs add a lot to
the ornamental garden. The
bulbs are ready to grow and
flower (or produce leaves) right
What are Summer Bulbs?
away, unlike many perennials
Summer bulbs all have that need to get established
some type of underground first. Many tender bulbs prostorage structure. They may duce spectacular, brilliant flowactually be bulbs that produce ers, adding a welcome splash
flowers, but also include some of color to the garden in mid to
heat-loving tropical plants such late summer. Most true bulbs
as the elephant ears, gingers have an annoying habit of
and more. Although commonly losing their leaves after they
referred to as ‘bulbs,’ there bloom, but the gorgeous foliage
are a variety of different un- of most tender bulbs remains
derground storage structures strong throughout the growing
(bulbs, corms, rhizomes, and season.
tuberous roots). All of these
structures function to store Selecting Summer Bulbs
food through the winter to boost
You can find summer bulbs
plant emergence and provide in stores and garden centers
the flowering structure the fol- from late winter through late
lowing season.
spring. Choose the biggest and
Summer bulbs are often firmest. Healthy bulbs are solid
referred to as ‘tender’ bulbs. and relatively heavy, so pick
They are planted outdoors after them up and check. If they feel
the last spring frost. In Wiscon- soft or extremely lightweight,
sin, the vast majority of sum- they may not grow well. Almer bulbs are not cold hardy most all bulbs will have nicks
and will not survive the winter and loose skins. Don’t worry
outside (but may be hardy in about that unless the bulbs are
warmer zones). These plants showing signs of mold or rot.
need to be dug at the end of Plant your bulbs as soon as
the season (or the containers the weather and soil conditions
brought indoors) and the stor- permit. If you can’t plant your
age structure kept indoors until bulbs right away, store them in
the following planting season. a cool, dry place.
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Starting Indoors
Most summer bulbs originated in the tropics and need
warm conditions and warm
soils to grow well. But in the
north that would mean waiting
until June or later – a bit late
to allow the plants to develop
completely during our relatively
short growing season. Gardeners in colder areas may want
to start their summer bulbs indoors and move them out once
the soil has warmed. This will
enable the plants to develop
and mature early enough to
give you a long season of enjoyment, generally blooming in
early to midsummer.
In most parts of North America, tender summer bulbs can
be started indoors four to six
weeks prior to the usual last local frost date and then planted
outdoors to begin their regular
summer growing season.
Choose clean containers
with drainage holes. Good
drainage is essential. Use a
commercial potting soil mixed
with equal parts peat moss and
a drainage material such as
sand or Perlite.
To start tender bulbs indoors, plant them in pots at
the recommended depth and
place them 6-12 inches below
grow lights or in a window or
greenhouse with bright light. If
possible, provide bottom heat
of about 70F. They will root best
and have the showiest blooms
if they are grown in soils between 65 and 75F. Exposure
to cold early in their develop-
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ment can stress bulbs and
make them more susceptible to
fungus problems and rotting, or
may even cause them to abort
their blooms. Keep soil moist,
but not wet.
Once the weather has
warmed and the threat of frost
is past, you can transplant
them into the garden or simply drop them with their pots
into decorative containers. A
general rule of thumb is place
them outside when you would
plant tomatoes. Summer bulbs
prefer warm soil, close to 60F.
Or as an alternative you can
purchase pre-sprouted plants
if you don’t have room or the
light to start your own indoors.
This will cost more, but you will
have a sturdy plant ready to put
in the garden.
Planting Outdoors
Remember you will have to
disturb the area each fall to dig
the tender bulbs, so summer
bulbs are harder to integrate
into permanent plantings of
perennials and woody ornamentals.
Amending your garden soil
is the key to making your bulbs
thrive. Before planting, add lots
of well-decomposed organic
matter to your soil—compost,
leaves, horse manure, or anything else that will enrich the
soil and provide unrefined nutrients. It’s best to do this before
planting: Till a 2-6inch layer of
organic matter into the soil.
Most bulbs, whether tender
or hardy, will do best when
planted at a depth of three
times the height of the bulb.
If gardening in heavy clay
soil, plant the bulbs shallower
than recommended, and make
up the difference in depth with
a thick top-dressing of mulch,
or sand and mulch after the
soil in the garden warms to
about 70F. This will conserve
moisture and keep the foliage
and flowers clean.
Trying to grow tropical
plants that need warm temperatures and sulk when it’s
too cold (i.e. below 50F) can
be a real challenge in cold,
northern areas. You have to be
more creative in finding homes
where these tender plants will
thrive – warm spots in a cold
climate. Choose protected
sites or use techniques to get
the soil warmed sooner, such
as using clear plastic over the
planting site to help elevate the
temperature, or just planting in
containers.
Overwintering
Since these summer bulbs
are not winter-hardy in our climate, they need special treatment to save for the next growing season. Many of them are
expensive, yet easy to keep, so
it is worth the trouble to dig and
store the underground portions
of these plants. But if you don’t
want to bother or don’t have a
way to store them, you can just
treat them as annuals. Summer
bulbs should be dug up in the
fall when they are dormant.
After the frost has damaged
the top growth, dig the bulbs.
Remove all foliage and lay
them out in a cool, dry location
for a week or two. Once their
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outside has dried, store them
in a cool, dry location for the
winter. If you grew your begonias or caladiums in containers,
you may want to just move the
containers indoors. Let the soil
dry out and store in a cool, dark
place until early spring when
you can begin watering them
again.
Caladium
Caladiums are bright, boldleafed plants grown mainly for
their foliage. They are native to
tropical South America (Venezuela, Colombia, Brazil). The
ones most commonly offered
commercially are Caladium x
hortulanum, a species of hybrid origin. Grown mostly for
their interesting foliage display,
caladiums perform well in garden borders and containers.
All have heart-shaped leaves
ranging in size from 6 to 12
inches growing from a tuber.
The numerous cultivars offer
foliage colors in red, salmon,
rose, white, or green with many
variegated combinations.
Caladiums prefer a rich soil.
Most cultivars are adapted to
full shade, but some tolerate
partial sun or early morning
sunlight. Full sun generally
reduces the intensity of the
foliage color of most cultivars.
Start the potato-like tubers
6 weeks before the last frost
date. Plant tubers individually
in 4-6” pots (or start in trays of
moist peatmoss and transplant
when the shoots develop).
Place the tuber with the eyes
up (the knobby side) 1½-2”
deep. The roots grow from the
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top surface of the tuber which
intuitively will cause many gardeners to plant them upside
down. To promote more leaves,
remove the largest bud in the
center of the root.
Elephant Ears
Elephant Ears is a common name given to a group
of tropical plants of several
genera — including Alocasia,
Colocasia, and Xanthosoma —
that produce huge, lush green
leaves resembling the ears of
elephants. Native to tropical
Asia, they are all members
of the arum family (Araceae).
These tubers can produce a
plant 3-5 feet tall in one season
with leaves over a foot across,
for a dramatic accent in the
garden, giving a tropical look.
They grow in full sun or light
shade and thrive during humid
weather. Ample soil moisture
is a must, especially if grown
in full sun. They can also be
grown standing the shallow
water of a water garden (up
to the pot edge). They should
be fertilized weekly. If your
elephant ears don’t produce
rapid lush growth, they need
either more heat, more water
or more nitrogen.
Start elephant ears indoors
up to 8 weeks before the last
frost in your area, placing the
blunt down, 1-2” deep. Depending on how they were stored it
sometimes takes them a while
to come out of dormancy.
Calla
Calla lilies are native to
South Africa, where the plants
How to Store Some Commonly Grown Tender Bulbs
Elephant’s Ear (Alocasia or Colocasia)
Both can be lifted before frost, potted and treated as a houseplant for
the winter. Feed lightly throughout winter and water often. Otherwise the
tubers can be cleaned and stored in peat moss. Check monthly and cut
away any soft spots that develop. Allow the remaining healthy portion to
dry before re-storing in peat.
Begonias, Tuberous
Dig before a hard frost (a light frost can be allowed to kill the tops). Let the
tubers dry for 1-2 weeks, with 2-5 inches of the foliage still intact. Remove
excess soil and foliage and store at 50ºF.
Caladium
Lift caladium plants before frost. Allow them to dry in a warm spot for
about a week. Cut back the foliage after it turns yellow. Store at a warmer
temperature than for most other tender bulbs, at 60ºF.
Calla
Dry the rhizomes of calla lilies for 2-3 weeks in a warm location, shake off
the soil and remove the dried stem. Store at 45-55ºF.
Canna
Allow frost to kill the tops, but they should not be subjected to a hard freeze
which turns the stem to mush. Dry the roots for a day or two. Cleaned roots
can be wrapped in newspaper (or layered in peat moss or other packing
material if your storage conditions are dry) and stored in paper bags or
cardboard boxes, at 45-50ºF. Check periodically to be sure the roots do
not dry out; increase the moisture level if necessary. Wait until spring to
divide, break apart, making sure there are at least 3 eyes per division.
Dahlia
Dig before a hard freeze, but their tops may be allowed to die back from a
light frost. The tuberous roots bruise easily, so handle with care. Although
some people prefer to divide the roots immediately after digging since the
eyes or buds are easier to see in the fall, it is best to wait until spring to
prevent spoilage in storage. Let them dry for several hours before placing
in storage. Check monthly for dehydration and mist lightly, if necessary.
Gladiolus
Lift the plants in the fall either when the plants yellow or after the first frost.
Shake off the soil, but do not wash, cut the stems back to 1-2” and allow the
corms to dry. Place them in bright sunlight for a day or two, then move them
to a well-ventilated location for about 3 weeks. Remove the old, shriveled
portion, keeping only the new plump corms, before packing for storage.
grow up to six feet tall in moist
areas. Cultivated plants grow
1-4 ft, depending on the variety.
White calla lily, Zantedeschia
aethiopica, grows 2-3 feet tall
with glossy, arrowhead-shaped
leaves. The leaves of some
species, such as the yellow
or golden callas, Z. elliottiana
and Z. rehmannii, are blotched
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with white or semi-transparent
spots. Funnel-shaped flowers are white, pink, rust, yellow, lavender, peach, apricot
or salmon. They bloom for a
month or longer in mid summer.
Calla lilies prefer full sun,
and rich, organic soils with
plenty of moisture. They can
be adapted to grow as marginal
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plants in water gardens or in
containers. After blooming and
when the leaves fade, allow the
soil to dry out for a few weeks.
Plant calla lily rhizomes 1-2
inches deep 6-8 weeks before
the average last spring frost
in your area. Calla lilies also
make great houseplants.
rhizome is started into growth,
the sooner it will flower.
Gladiolus
Gladiolus is an African genus with many species conDahlia
tributing to the types grown as
Dahlias offer a great deal of ornamentals. Gladiolus come
variety in the garden. From July in a wide color range and can
to October, this tuberous root grow from one to five feet. They
produces 2-8 foot plants with make excellent background
flowers 8-12 inches across. plants with a strong vertical
Offering a wide range of colors, aspect with their long flower
Canna
blooms shapes, sizes and plant spikes. Only one flower stalk
Although this bright, bold- heights, dahlias are sturdy, reli- is produced per corm. They are
leafed tropical plant is now able bloomers. There are two often grown aas cut flowers.
naturalized in many tropical basic types of dahlias, border
The size of the plant and
countries of the world, can- and bedding. Border dahlias spike produced is directly renas originated in the Mid- are large plants that are grown lated to the size of the corm
Americas from Florida to the from tubers that are kept from that is planted. Plant corms 4-6
warmer parts of the countries year to year. Bedding dahlias inches deep in full sun. They
of South America. These tropi- are compact, mound growers can be planted started in midcal herbaceous plants provide that are produced from seed spring over a two month period
masses of dramatic foliage as each year. They form a tuber to stagger the bloom period.
well as bright, colorful blooms by the end of the season, but Staking may be needed.
throughout late summer and they do not store well.
fall. Traditionally, cannas grew
Dahlias thrive in full sun in Tuberous Begonia
3-8 feet tall, with red, pink, our area and prefer moist, wellTuberous begonias are best
yellow, orange and cream drained soil.
known for their showy flowers.
flowers. But new hybrids and
Plant the fleshy light brown These hybridized plants with
selections include shorter and tubers horizontally about 6 large leaves and fleshy stems
dwarf forms. All varieties can inches deep and 18-24 inches originated from South Amerireadily be grown in pots and apart. Larger types benefit can species with large pink
tubs, but the smaller varieties from staking; put stakes in at and yellow flowers. Cultivated
are particularly suited to pot planting time to avoid damag- tuberous begonias come in a
and patio cultivation, where ing tubers.
range of flowers sizes, shapes
they will begin to flower early
Use a low-nitrogen fertil- and colors.
while still quite short.
izer and use sparingly so as to
Grow tuberous begonias
During the growing and not promote leaf growth over in rich, moist soil in full sun to
flower season, cannas require flower growth. To encourage partial shade as bedding plants
little attention and usually don’t the growth of bushier plants or in containers. Fertilize every
require staking. Plant in full sun pinch out the center shoot just two weeks. Protect from strong
in well-drained soil. Fertilizer above the third set of leaves.
wind, stake to keep the fragile
monthly.
Tubers can be started in- stems from breaking, and keep
Start canna rhizomes in- doors 6-8 weeks ahead, but well watered. Pinch out the
doors 4-6 weeks before the are often planted directly in primary growing tip at about 2
average last frost date in your the garden once all danger of inches high on basket varieties
area in large pots. Place them frost is past. Bury the tuber, but to ensure that there are lots of
3-4 inches deep; there is no leave the crown exposed at the branches that hang gracefully.
“right way up”. The earlier a surface of the potting mix.
Larger, double male or center
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Garden Expo 2013
flowers will develop if the two
side single female flowers are
removed as plants develop.
Plant the enlarged hypocotyls (“tubers”) indoors 8 weeks
before the last frost (or when
pink sprouts appears). Place
the concave or indented side
upward with the tubers at or
just below soil level (they rot
easily if planted too deep.)
Other Summer Bulbs
There are many other tender plants grown from bulbs or
other storage organs.
Acidanthera or Peacock
Orchid is actually a gladiolus,
Gladiolus murielae. It has fragrant, 2-3” wide white flowers
with a purple blotched center in
late summer. Plants grow about
2 feet tall with upright, sword
shaped leaves
Agapanthus or Lily-ofthe-Nile, from South Africa is
a rhizome that produces round
clusters of blue or white flowers
in mid to late summer on tall
stalks. Plants grow up to 40” tall
(height varies by variety). This
plant is best grown in containers in Wisconsin.
Montbretia (Crocosmia
species from South Africa) is
a corm that produces spikes
of 1-2” bright red, orange or
yellow flowers in mid-summer
for about 4 weeks. The swordshaped leaves grow 24-36” tall
Pineapple lily (Eucomis
spp.) is a true bulb that grows
1-1/2 to 2 feet tall with strap-like
foliage and bottle brush-like
inflorescences.
Gloriosa or Climbing Lily
(Gloriosa rothschildiana) is another South African native. This
is a climbing vine that grows to
6 feet and produces yellow and
red flowers that look like lilies
in late summer.
Peruvian Daffodil (Hymenocallis narcissiflora) produces clusters of fragrant, 4”
white flowers with slender,
petal-like segments surrounding the central cup of the flower.
One variety, ‘Sulfur Queen’,
is a beautiful pale yellow.
And many more...
• Alstroemeria, Peruvian lily
• Bletilla striata, Chinese
ground orchid
• Freesia hybrids
• Galtonia, summer hyacinth
• Ixia, African corn lily
• Nerine, Guernsey lily and
others
• Ornithogalum, Star of Bethlehem
• Polianthes tuberosa, tuberose
• Scadoxus (=Haemanthus),
blood lily
• Sparaxis tricolor, harlequin
flower
• Tigridia pavonia, tiger or
Mexican shell flower
• Watsonia, bugle or sword
lily
• Zephyranthes, rain lily
Resources on Summer Bulbs
Summer-Blooming Bulbs, edited by Beth Hansen (Brooklyn Botanic Gardens, 2001) 112 pages
— chapter topics include botany, care, design and a mini-encyclopedia.
Summer Bulbs: Simple Steps for Growing Beautiful Glads, Dahlias, Begonias, Cannas,
and Other Tender Bulbs, by Henry Jaworski (Houghton Mifflin, 1998) 128 pages
Taylor’s Guide to Bulbs: How to Select and Grow 480 Species of Summer-Hardy and Tender Bulbs, by Barbara W. Ellis (Houghton Mifflin, 2001) 439 pages — includes spring bulbs
and tender bulbs to grow for summer color—or in containers, with detailed instructions on
propagating bulbs, how to overwinter tender bulbs, forcing bulbs for indoor flowers, and more.
Summer Flowering Bulbs — Ohio State University Extension Fact Sheet HYG-1244-92
ohioline.osu.edu/hyg-fact/1000/1244.html
Year-Round Care of Summer Bulbs — Brooklyn Botanic Garden
www.bbg.org/gar2/topics/plants/handbooks/summerbulbs/4.html
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