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Crazy Snake Worms By Dawn Pettinelli “It may be doubtful whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.” – Charles Darwin A BOUT 6 or 7 years ago, when I finally got around to edging, weeding and mulching the picket fence dahlia beds in mid-August, I encountered a most peculiar phenomena. As the soil-grass continuum was sliced by my spade to create a deep ‘V’ between the beds and the lawn, out sprang (quite literally) large, writhing, snake-like creatures. In fact, at first, I thought they were baby snakes but upon closer examination, they turned out to be earthworms. Now I have been gardening for more than half a century and never have encountered such distinctive, quick- moving worms and was not sure what to make of them, except to think that this is not normal. A couple of years later, at an international conference of soil scientists, I was perusing the poster sessions and stopped at one by Josef Görres, a professor from the University of Vermont, on the effects of invasive earthworms on forested areas in Vermont. There, before See color photo on page 27 my eyes, were pictures and descriptions of the culprits and of evidence of the damage they wreak when allowed to enter native New England woodland areas, as well as the kind of trouble they were causing in my gardens. As a longtime gardener, I was always happy to find earthworms in my beds and lawns. After all, aren’t earthworms the gardener’s friend? Don’t they till the soil as they tunnel through it consum- ing bits of organic matter and mineral soil? Their holes allow air and water to penetrate deeper into the soil to benefit plant roots. Their casts (droppings) are rich in nutrients and microbes that encourage plant growth. They incorporate and mix organic matter into the soil, which aids in the formation of good soil structure as well as increased water holding capacity. What’s not to like? Just as in real estate, the answer to that question is dependent on location, location, location. A lot of us don’t remember what we had for dinner yesterday so, based on that rationale, even more of us probably forgot that our state was covered by a glacier until about 15,000 years ago. (See box below on Glaciation in Connecticut.) Any native earthworms were either forced south or obliterated by the glacier. So where did the worms we now find in our gardens come from? Most likely not from more southern locations, as GLACIATION IN CONNECTICUT Compiled by Will Rowlands G laciers have ravaGed the topography of New england and connecticut for millions of years. The last major glaciation advanced as far as southern long island some 21,000 or 22,000 years ago. at that time the laurentide ice sheet covered eastern canada and New england. connecticut has experienced a number of ice ages. some suggest there may have been as many as 10-20 glacial periods in North america over the last 1 or 2 million years. check it out yourself. Find an outcrop of bedrock and look for glacial striations. Glaciers carry massive rocks and boulders that gouge grooves in the bedrock as they advance. The signs are unmistakable and give the glacier’s direction of movement, generally north to south. dating of recent glacial events is possible through carbon dating of organic components in glacial deposits. They can also be dated by varves, which are layers of sediment deposited seasonally in glacial lakes that can be counted like the growth rings of a tree. relative temperatures, up to almost a million years ago, can be estimated by analysis of oxygen isotope data obtained from deep sea core samples. long island is actually a moraine composed of glacial till, the material picked up by the glacier as it advances. When a glacier recedes, it melts and drops whatever material it was carrying in a terminal (or end) moraine. There was so much material left behind when the last glacier melted and retreated that it created a dam and a freshwater lake from the meltwater (lake connecticut) in the area that is now long island sound. The captain islands, Block island, Falkner island, Martha’s vineyard, long island, Nantucket and the Norwalk islands are all glacial deposits. September/October 2014 sea level was lower at that time, as much of the earth’s water was tied up in continental glaciers. When the glaciers melted, sea level rose, eventually flooding lake connecticut and creating long island sound. Glacial periods tend to repeat in 100,000-year cycles. More recently, we’ve seen some 40,000-year cycles. The alternating glacial and interglacial periods are believed to be driven by overlapping cycles in precession (direction of the earth’s axis), obliquity (tilt of the earth’s axis), and eccentricity (shape of the earth’s orbit). as you might suspect, how the earth absorbs, or reflects, solar radiation from the sun is a major factor in determining the frequency and length of ice ages. historically, warm periods have been the exception and cold ones the rule. right now, we’re 12,000 years into an interglacial warming period. The last interglacial lasted 20,000 years. When you think about ice ages, consider how native soil organisms and plants were displaced and/or killed off. The laurentide ice sheet was probably around 2,000 feet thick in connecticut and several thousand feet thick in northern New england and eastern canada. like huge bulldozers, glaciers scraped off 60 feet or more of surface material and destroyed entire ecosystems in the process. The average depth of the residual glacial till left in New england is around 10 feet. as connecticut has been subjected to advancing and receding glaciers a number of times, it should come as no surprise that we don’t have any native earthworms. 짮 Will Rowlands has a BS in geology from Dalhousie University in Halifax, Nova Scotia, and is a UConn-certified Advanced Master Gardener. 24 Connecticut Gardener Crazy Snake Worms earthworms move about a half mile every 100 years, so they would not have reached our New England forests yet. Earthworms and their cocoons came along with the plants that our early European ancestors brought over with them or imported. A second mode of intercontinental earthworm travel was in ship’s ballasts, which were emptied on shore for weight adjustments before leaving port. Two common Connecticut earthworms, also found in Europe, are Lumbricus terrestris (nightcrawler) and L. rubellum (redworm). There probably are at least a dozen more earthworm species of European origin in Connecticut, according to Dr. Görres, as he has documented 14 of them in Vermont. These early European immigrants were right at home – and even productive workers – in cultivated gardens and fields. As they consumed soil, soil microbes and organic matter, they made nutrients more available to plants, as well as improving the soil’s drainage and other properties of interest to cultivated, non-native plants. Worms may influence the soil’s pH as well, as some species of earthworms contain calciferous glands and their casts may contain considerable amounts of calcium, a base cation. The USDA estimates that an acre of soil may contain 500,000 earthworms, though other sources say closer to one million, and that these creatures can move up to 5 tons of soil per acre every year through their bodies. A Cornell University website states that the earthworms in an acre of soil can produce 700 pounds of casts a day. That is an extraordinary amount of activity taking place right beneath our feet! And in some locations, most especially forested ones, this is a problem. Soil and forest scientists have recogcontinued on next page EXPERIMENTS IN GARDENING: Battling Invasive Earthworms By Kathleen Nelson i first encountered Amynthas worms in the fall of 1992. a friend and i were replanting a garden for a client. every time we stuck a trowel in the ground, dozens of fast-wiggling worms bubbled out of the ground. Other gardeners noticed the same. We were all delighted – earthworms, we knew, were good. somewhat later, i heard rumors that earthworms weren’t so good: they aren’t native and they’re damaging our forests. at first it wasn’t easy to find information but, eventually, i found people studying the problem. it wasn’t only forests – gardeners were reporting problems, too. There didn’t seem to be a solution. i spent hours on Google looking for ideas. Gardeners reported mixed success with diatomaceous earth. scientists noted that earthworms do not thrive in acidic soil. My own thought was – do NOT feed them tasty mulches year after year. My gardens were suffering. My garden soil, lovingly prepared with lots of deeply dug organic matter and carefully mulched with wood products each year, had become a sea of worms. My perennials were not doing well. Only fast-growing annual weeds thrived. Amynthas worms are apparently “annual” worms, a new population growing from overwintered eggs each season. By late summer, with each step i’d sink inches-deep into the soft soil. i could reach into the soil with my bare hands and pull up a handful of a dozen or more giant squiggly worms. i read of commercial growers who could no longer raise hosta in their gardens. My most-affected garden was a shady mulched bed with annual weeds and unhealthy perennials. Being impatient, i threw everything at the problem garden. in 2010, i weeded it, then sprinkled the 40 x 40 foot area with diatomaceous earth and sulfur pellets. i mulched with buckwheat hulls, an expensive oatmeal-sized mulch that doesn’t seem to rot. i looked at what was growing well in other areas with worm problems and decided to propagate 15 flats of the native running groundcover, Tiarella cordifolia, to plant the next spring. That garden is amazing now. Tiarella covers the ground between larger, healthy, mostly-native perennials. i don’t need Connecticut Gardener mulch. i don’t sink in when i walk on the ground. i can’t reach into the ground with my bare hands. recently, i needed worms for an invasives exhibit and could only find a few. The soil ph is now 5.2 or lower (5.2 is the limit of my ph test kit), down significantly from 6.4-6.8 in my other garden beds. did one or more of these treatments help? if so, which? Would my sunny perennial beds survive a ph of 5.2? did the diatomaceous earth damage the worms? did it damage other critters? is it safe to broadcast diatomaceous earth over such a large area? Maybe next time i’ll skip that. i no longer add compost to anything. i have no idea what we can do with the giant pile of garden waste in the back of our property but for sure i’m NOT going to use it to feed the worms. Where i need mulch, i use either buckwheat hulls or, in rock garden areas, crushed rock, though i still use shredded cedar mulch for paths. My newest gardens were planted by hacking small holes into the dry compacted soil of the old nursery paths, then shoving in the plants. These gardens are doing splendidly. The new gardens contain native woodland plants and dry-meadow plants – would this method work for more ordinary perennials? Meanwhile, i’m experimenting with native groundcovers, mainly Phlox stolonifera, between the larger plants in my older, sunny perennial beds in the hope of weaning the garden from mulch. in 1988, i was the cover girl on the first issue of Fine Gardening magazine. My article about how i became a gardener emphasized my discovery of mulch and how that made gardening possible. Garden books told me that i should be able to dig in well-prepared soil with bare hands. and i could. Now we have invasive Amynthas earthworms, and my methods have changed. This is the story of an experiment. i don’t know if one or more of the treatments is responsible for the success of that garden bed today. i’m not quite ready to recommend my methods to others. But, so far, the treated garden and the new mulch-free compost-free gardens are a success. My favorite worm website is Great lakes Worm Watch, www.nrri.umn.edu/worms 짮 Kathleen Nelson, a former nursery owner, is the chairperson of the Invasive Species Advisory Committee of Mad Gardeners. 25 September/October 2014 Crazy Snake Worms nized the role that earthworms have played in soil formation since at least the end of the 19th century, when assigning mor, moder and mull terminology to describe the integration of the humus or organic component of forest soils with the underlying mineral layer. Briefly, a mor forest floor layer would typically be found in conifer forests and consist of a notable litter layer with little mixing with the mineral soil underneath, while a mull forest floor would be less thick, more typical of deciduous forests, and show some signs of the mixing of organic materials and mineral soils by a diversity or organisms, including earthworms. Moder would be somewhere in between. In the 1980s, the Institute for Ecosystem Studies in New York wanted to examine the health of forest ecosystems and created a 100-mile gradient from New York City to rural Connecticut. One of the scientists noted areas with hardly any leaf litter and copious amounts of earthworms. This was not a desirable finding in northern forests. Our native woodlands evolved over the last 10,000 years or so in the absence of nature’s rototiller, the earthworm. In undisturbed forests, the litter from trees, shrubs and herbaceous plants forms a protective cover over the woodland soil. The litter layer (duff) breaks the force of raindrops, preventing soil erosion, and retains moisture for plant roots and other forest creatures. It provides lodging for many species of fungi critical for forest tree survival, and fornumerous insects and animals such as salamanders. The litter layer serves as a seedbed and nursery for trees like our beloved sugar maple, and for wildflowers like trilliums and bloodroot. Decomposition occurs slowly, mainly through the actions of decomposer fungal species and invertebrates. Lift up a handful of litter in an undisturbed forest floor layer and you’ll find the delicate white fungal hyphae coursing through the accumulated September/October 2014 — continued from previous page leaves, needles, twigs, branches and other organic debris. Since decomposition is slow, nutrient release is slow. Trees are conservative creatures, internally recycling many nutrients before shedding leaves or needles. This and other features are adaptions to life in low-nutrient, acidic soils naturally occurring in many areas of New England. Enter the earthworm. The earthworm’s goal is to turn organic matter into soil. While this may be desirable on cultivated lands, it is definitely a detriment in forested areas. As the litter layer is consumed, the bare soil is exposed to rain and wind, and erosion increases. Nutrients held tight in the litter are changed into available forms as they pass through the gut of the earthworm and any nutrients not taken up by plants can be leached into the soil and into water bodies. Seeds of forest trees and flowers no longer have a germination bed and, lacking the cover of the litter layer, are also exposed to increased predation. As the earthworms turn soil and organic material into casts the soil becomes more and more aggregated with the increase in aeration, causing it to dry out. Native plants struggle, but conditions are perfect for many invasive plant species, like garlic mustard and honeysuckle, to move in. And it doesn’t take long for these changes to occur. According to Dr. Görres, “Within a decade or two, the worms can essentially change the soil profile into something like the black, mineral-rich soils that are found in many European forests.” In addition, once the understory is disturbed and most of the annual vegetation is lost, deer may start grazing saplings of the canopy species. This 26 MORE INFORMATION www.vtinvasives.org/otherinvasives/earthworms www.uvm.edu/~entlab/Greenhouse% 20IPM/Workshops/2014/InvasiveEarth worms.pdf www.nrri.umn.edu/worms www.epa.gov/osp/tribes/NatForum10/ ntsf10_2m_Knowles.pdf www.harringtonsorganic.com/wpcontent/uploads/2013/11/CT-InvasiveWorms-vers-10-4-11.pdf may suppress forest regeneration. As if the European worms weren’t causing enough problems in our northern forested ecosystems, about 70 years ago or so, another genus of earthworms, Amynthas, from Asia started being detected in New York greenhouses. These are large, turgid, fast-moving earthworms with A. agrestis seemingly most common. Amynthas species can only be identified by dissection. Because of their frenetic movements when disturbed they are often referred to as Alabama jumpers or crazy snake worms. If you were to grab an adult by its posterior end, the body will break away from the tail, leaving you with a squirming piece of worm in your hand and a surprised look on your face while the rest of the worm quickly slithers away. Not only are the Amynthas launching an accelerated assault on our forested areas, they are causing problems on residential lots as well, with lawns, perennial, and ornamental beds seeing the brunt of the damage. Sites rich in organic materials like compost, leaf mold and bark mulches are all fair game. The excessively well-aggregated soil they create dries out quickly because of increase air circulation and loss of that protective, moisture retentive mulch layer. This disrupts root growth and also Connecticut Gardener Crazy Snake Worms the soil microbial community with which many plants have formed mutually beneficial (symbiotic) relationships. Curiously, I have found that my garden beds invaded by Amynthas all have Jack-in-the-pulpits growing in them. This has been noted by others, who also found Pennsylvania sedge as an indicator of earthworm disturbance. While we do not know the extent of Amynthas spread in Connecticut, if it follows the pattern in other states where surveys were conducted, the earthworms generally follow human activity. Most likely, as with their European predecessors, they arrived via the horticulture and shipping industries. Once here, earthworms and their cocoons can be spread by fisherman who dump their unused bait by the lake, in compost, mulch and topsoil purchases, in the soil stuck in the wheels of ATVs and other off-road vehicles, in potted plants from your friends or purchased at local plant sales, garden centers or big box stores, and by logging trucks and other vehicles that travel to and from forests. Also, earthworms can be purchased online and are often advertised as fish bait, vermicomposting worms, or touted as something to be added directly to your garden soil to make it more porous and enhance the health of your plants! (If you’re looking to purchase worms for vermicomposting, only buy those listed by their Latin name, Eisenia foetida.) Current research is being focused on the distribution of Amynthas species, their devastating and far-reaching effects on forested ecosystems and on control methods. As of now there is no effective control measure. In some cases, pesticides have been tried which do kill the worms but probably a lot of other organisms, and once the pesticide degrades, more worms will probably move back in. Dr. Görres is experimenting with some naturally derived control agents. Sulfur used at about 6.5 ounces per square yard reduced earthworm populations in another researcher’s experiment, but keep in mind that sulfur will also lower the pH of your soil. Kathleen Nelson, chairperson of the Invasive Species Advisory Committee of Mad Gardeners, Inc. in western Connecticut has been battling Amynthas on her property for many years. (See box on page 25.) Instead of quickly-degrading wood mulches, she now uses buckwheat hulls or gravel. Her current approach is to stop amending the soils with organic materials and find plants, such as tiarella, which can tolerate unamended Photo / Josef Görres, University of Vermont crazy snake Worm (Amynthas agrestis) in the wood mulch of a horticultural bed at a tree nursery in vermont. check out the white ring around the worm’s body. in Amynthas species it stretches all around the body and it is well offset from the rest of the body. Connecticut Gardener 27 native soils. That might be a suggestion, much to many gardeners’ dismay, that we should think more about. If we mostly grow native plants, which tolerate our native soils, we would not have to add copious amounts of organic matter and mulch to have great gardens because, by doing so, we’re just creating invasive worm magnets. Also, native plants tend to prefer low pH or acidic soils and earthworms do not. If mulching is imperative, it is thought that mulches with high carbon to nitrogen ratios may be less appealing to earthworms. One of the UConn Master Composter interns, William Flahive, wrote an article about a homeowner sparring with the Amynthas that took over and destroyed their lawn. He called the situation, “depressing” and I totally agree with him. When we can’t even control the garlic mustard or bittersweet we see above ground, how can we control a creature below ground that is only seen when dug up? The best we can do at the moment is educate ourselves, inform others and take care not to participate in the spreading of these destructive earthworms. UConn’s Master Gardener and Master Composter programs will soon issue a survey in which gardeners will be asked to let us know where they have Amynthas species. This will be a first step to understanding where we might need to intervene to manage this invasive species. 짮 Dawn Pettinelli is an assistant cooperative extension educator in the Department of Plant Science at UConn. She manages and coordinates the activities of the UConn Home & Garden Education Center and the UConn Soil Dawn Pettinelli Nutrient Analysis Laboratory. September/October 2014