Tuesday afternoons in the woods

by Sandy Garland

When our ash trees were taken down last spring, not only did they leave enormous “holes” in the Old Woodlot, but they also caused damage to other trees and plants when they fell and were dragged out of the area. Increased light means the ground vegetation is likely to change. All this prompted us to form a regular work group to restore this habitat and create a mixed woodlot full of a variety of native plants, shrubs, and trees.

A small group of us have been tackling this work, a bit at a time. Here are some successes and some things we’ve seen.

Over the last few weeks, a priority has been to remove Garlic Mustard, especially plants that are blooming as we want to prevent any more seeds from planting themselves. Garlic Mustard is an invasive species that is especially a problem in woods. See our fact sheet and photos.

Dog-strangling vine (DSV) is the most difficult invasive species to control. In fact, we don’t seem to be able to control it at all. Our goal is to at least keep the plants that are already in the woods from producing seeds. Mirko proved to be very adept with a scythe last Tuesday and cut a lot of DSV that was just starting to bloom. We’ll have to cut these same plants again in a month and probably once more in late summer as they grow back quickly. But if we can deplete the resources the plant stores in its roots, we might gain a few “points” in the battle. See our fact sheet and photos.

Newly scythed Dog-strangling Vine. Cutting gives grasses an advantage as they grow back faster than DSV.

Newly scythed Dog-strangling Vine. Cutting gives grasses an advantage as they grow back faster than DSV.

Glimpse of a gartersnake photographed by Kate Davis

Glimpse of a gartersnake photographed by Kate Davis

Kate chose to dig up DSV as that’s the only way to truly get rid of it. We dig it out around “good plants,” but it would take an army to do this all through the garden. In this area, goldenrods, blackberries, native clematis, and other wildflowers are competing with DSV. We’re on their side. While working, Kate found this gartersnake that seems to live on the south edge of the woods.

Another way to fight DSV is to cover thick patches of it with a tarpaulin. The tarp has to be left in place for more than a year to make sure the plant roots are killed. Last week, Catrina and I moved a tarp from this area to an adjacent one. I was very pleased to see that blackberries from nearby had grown runners under the tarp and were now sending up new shoots. You can just see blackberry flowers at the right of this photo. And you can just see the tarp in its new location in the background.

After killing DSV by covering it for more than a year, we were delighted to find blackberries growing into this now bare area

After killing DSV by covering it for more than a year, we were delighted to find blackberries spreading into this now bare area

Names of plants

A mass of Large-leaved Asters

A mass of Large-leaved Asters

In addition to invasive species, we’re all learning the names of the “good” plants. At the left are Large-leaved Asters (Eurybia macrophylla; see our database), a good ground cover in shady areas. They DO bloom, in late summer and early fall, usually just before Heart-leaved Asters.
Jack-in-the-Pulpit on the left growing right next to White Trilliums (right)

Jack-in-the-Pulpit on the left growing right next to White Trilliums (right)

At the left are two spring ephemerals, both of which have three-part leaves: Jack-in-the-Pulpit (Arisaema triphyllum; database) and White Trillium (Trillium grandiflorum; database).

Interesting sightings

We learned that Kate’s the one with sharp eyes – and a great cell-phone camera. She spotted and photographed a huge spider (not sure what species), a morel mushroom growing in our plant nursery, and a colourful American Toad (Anaxyrus americanus).

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Help wanted

With Ted off in Europe and Gene visiting grandchildren, we are down two valuable people from our Old Woods team. If you’d like to help, please come along any Tuesday afternoon at 1:30 pm. Even helping for one afternoon is important.

Birds and insects in the rain at FWG

by Christine Hanrahan

Dodging the rain showers and gusty winds, I spent several hours walking around the garden looking for birds, plants, insects… Naturally, the latter were scarce and had to be looked for under leaves, huddled against stems and branches, seeking shelter from the rainy weather. I did see a pretty common spring moth in the Backyard Garden (BYG), but it flew off before I could photograph it. If you are interested in seeing this black and white beauty, there is a photo from a few years ago here.

Also in the BYG, one of the impressively large green blister beetles with vivid orange legs. Elsewhere, a few flies, including a syrphus sp., some bumblebees, and a few of the tiny Publilia treehoppers with their attendant ants. In another week, these insects should be more numerous.

One of the benefits of sometimes letting a week go by between visits is that you can be properly astonished by the sheer rate of plant growth, something that is less startling when you visit the site daily. Thus, last week I saw the small comfrey plants sitting a few inches above the ground, and today they were fully grown with flower clusters opening. It was quite a transformation of the land, both along comfrey alley (near the pond) and of course, elsewhere. Where oaks were putting forth tiny soft leaves last week, now they are big and bold, ditto for the black maple leaves, and indeed for most of the others. Bloodroot is long gone, save for the leaves, and the trilliums are on their way out. Mayapples are in flower (look under the leaves for their large white blooms).

In the BYG, there are yellow lady’s-slippers, drifts of blue forget-me-nots, the tiny native dwarf iris just starting to flower, and the two similar Geums, prairie smoke and water avens, both in flower with a few going to seed.

Gray treefrogs are calling from various spots around the garden.

New bird arrivals since my last visit include gray catbirds, least flycatcher in the ravine, great-crested flycatcher in the new woods, common yellowthroat (a warbler), a ruby-throated hummingbird vigorously chasing a tree swallow (!), and a lone male canada warbler foraging for insects on an apple tree. I got a great look at this beauty with its black “necklace.” Canada warbler is considered a species at risk, federally and provincially, having undergone a long-term decline. Very sad.

Other birds noted include barn swallows, tree swallows, chickadees, nest-building cardinals and red-winged blackbirds, grackles, robins, a couple of ravens who flew over to Carleton U, where they must be nesting, crows, mourning doves, goldfinches, phoebes still on nest (good), yellow warblers, starlings, baltimore orioles singing from every corner of the garden, and a roof full of rock pigeons (red barn). No sign of either kestrels or green herons today. A mockingbird was seen by others in recent days, but not by me, alas. These birds turn up at FWG and the adjacent Arboretum every few years.

On a more sombre note, the small rototilled area in the old field is thickly carpeted with garlic mustard seedlings. Seedlings of other plants are there too, but the mustard dominates. Also making an unwelcome reappearance is lamium. This common garden plant spreads rapidly and is very hard to get rid of once established. It has been at that location for about 12 to 14 years, another legacy of the temporary leaf dump, which also gave us celandine, though the latter is not a problem here. The lamium, I confess to having in my own garden, because its silver and green foliage lights up shady sites, and it grows where a lot of other things do not. It also has very pretty yellow flowers in spring. However, let it escape into a natural site and it can become a nuisance. Indeed, I expect there are gardeners who wish they’d never let it into their gardens!

Lots more photos on the May Blog

Garlic Mustard – Ecology and Control Methods

by Christine Hanrahan

Garlic mustard (Alliaria petiolata) is recognized as a serious invasive plant species in North America. Native to Europe, the plant was brought here by settlers for food and medicinal purposes. It has been present in North America for over 140 years, apparently first recorded in 1868 on Long Island in New York State and in Canada (including Ottawa) in the late 19th century. Since then, it has had a long lag period, sitting quietly, doing nothing, until about 40 years ago, when it began to spread rapidly, alarming naturalists and biologists alike.

The plant is most abundant in southwest Ontario, but can be found all along the St. Lawrence Valley and, of course, throughout Ottawa.

Garlic mustard is found in forests, edge habitats, along trails, roadsides, and in just about any disturbed area. It grows in shade, sun, damp conditions and dry, although it prefers dry, wooded locations.

Biology of Garlic Mustard
This early spring plant grows rapidly. In the first year of development, only basal “rosettes” are visible, but by the second year, when they reach maturity, the plants can reach a height of 1 to 1.5 metres. A biennial plant (a 2-year life-cycle), it self-pollinates and is cross-pollinated (by insects) and spreads only by seed.

Seeds usually germinate in the second year, although they can remain viable in the soil for 5-10 years; seed viability apparently decreases over time. Long exposure to cold is needed for germination to occur; thus our winters are perfect. Individual plants can produce anywhere from about 350 (usual) to 8,000 seeds, and the germination rate is 40-100%. Although seedling mortality is high (only about 2-7% survive) and drought can kill off 95% of seedlings, none of this seems to prevent the spread of garlic mustard.

The problem with Garlic Mustard….
Garlic mustard is a habitat generalist; it seeds prolifically and has no natural enemies in North America. It displaces native plants (especially spring ephemerals) and decreases diversity, which in turn decreases available food for wildlife (pollen, nectar, fruit, foliage, roots). It probably also decreases suitable habitat for ground-nesting birds, such as ovenbirds and hermit thrushes, when it is the dominant understorey plant.

I read somewhere that in a highly infested area, seedling density may reach 17,000 in half a square metre. Even it only 2-7% survive, this is still a lot of garlic mustard. In one local site with a high diversity of native plants, particularly spring ephemerals, garlic mustard was first noticed about 12 years ago; within 5 years, it had almost completely dominated the area to the detriment of native flora.

It has been found to disrupt the symbiotic relationship between tree seedlings and arbuscular mycorrhizal fungi (mycorrhizae colonize root systems and are critical for nutrient and water uptake). In recent years, high concentrations of cyanide compounds have been discovered in garlic mustard, and these compounds may contribute to the reduction in mycorrhizal fungi.

Studies have shown that the growth of sugar maple (Acer saccharum), red maple (A. rubrum), and white ash (Fraxinus americana) is poor in soils invaded by this species. Worse, the negative impact of garlic mustard on the soil and on arbuscular mycorrhizal fungi continues for several years after the plant is removed from a site. Not all tree species are affected, and further studies are ongoing.

Garlic Mustard Control Methods
Control of this plant is both easy and difficult. It is easy to pull up, but difficult to completely eradicate. At the Fletcher Wildlife Garden (FWG), we’ve been pulling it out for years. Initially, we thought we’d eradicated it, as it didn’t reappear for several years. But disturbed soil facilitates seed germination, and it came back in areas where we’d been removing it and other invasives.

Management options vary depending on the size of the infestation. For a small stand, pulling is feasible. For large areas, methods proposed by those who deal with this problem regularly include herbicide use (usually 1-2% glyphosate) and controlled burns. Neither of these is particularly desirable, although both can have some impact.

Pulling is easy to do (especially when the soil is damp), quick, and requires no special tools. However, this disturbs the soil, which encourages further growth from the seed bank. You also need to ensure that the entire root is pulled up (see photo of the long roots below). Nonetheless, this is the easiest method for smaller infestations, such as we have at FWG.

Cutting is often suggested for large areas of garlic mustard, particularly if nothing else is growing with it. Scythes, weed whippers, even lawnmowers are three tools that work best for cutting many plants at once, particularly as they must be cut at ground level. This needs to be done after flowering (earlier, and they may re-sprout), but before seed production.

Hoeing up the basal rosettes could help prevent plants from growing and setting seed, but we’ve not tried this at FWG, yet.

No matter the method you choose and whether you have few or many plants, follow-up control is critical. Your goal is to prevent seed production AND deplete that seed bank. You will likely have to do follow-up work for at least five years and, in most cases, much longer. Studies suggest that single-year control efforts are worse than no management at all, because the resulting soil disturbance creates perfect growing conditions for garlic mustard, aids in growth and distribution, and exacerbates the problem. Without follow-up control, it is probably better to do nothing!

Disposal is important too. If you have cut or pulled plants when seedpods are just forming, don’t leave them on the ground, as seeds will continue ripening. Place them in plastic bags and dispose of in garbage. Not an ideal method, but composting in a small home composter, or leaving on the ground, will nullify all the work you’ve put into removal! Creating a big pile and covering it with a tarpaulin may work to control seed production if the tarp is well secured. Basal rosettes dug or hoed up, can be left on the ground.

Other Plants Similar to Garlic Mustard
When removing garlic mustard, remember that many other common plants can closely resemble their leaves and flowers. Early saxifrage (Saxifraga virginiensis) and toothwort (Dentaria diphylla), both have small white flowers similar to garlic mustard. Leaves of yellow avens (Geum allepicum), barren-ground strawberry (Waldsteinia fragarioides), violets (Viola), and non-native motherwort (Leonurus cardiaca) can be mistaken for garlic mustard.

Bio-control
In Europe, 69 species of insects are known to feed on garlic mustard. Efforts to find bio-control agents for North America began in Europe in 1998, and several weevil species look quite promising. One, Ceutorhynchus scrobicollis (a root miner), has been in quarantine at the University of Minnesota (with two other weevil species)for several years, and if all goes well, it will be reared for release sometime in the next few years. The two other weevil species in quarantine, C. alliariae and C. roberti, are shoot-mining weevils. A fourth, being studied in Switzerland as quite promising, is a seed feeder.

References
Friends of the Patapsco Valley and Heritage Greenway, Inc., 5th Annual Garlic Mustard Challenge.

Gerber, E., Cortat, C., Hinz, H.L., Blossey, B., Katovich, E., Skinner, L. 2009. Biology and host specificity of Ceutorhynchus scrobicollis (Curculionidae; Coleoptera), a root-crown mining weevil proposed as biological control agent against Alliaria petiolata in North America. Biocontrol Science and Technology, 19(1-2).

Mabry, C. 2007. Background and methods of control for garlic mustard. A Report Prepared for the Sierra Club.

Nature Conservancy of Canada. 2007. Control methods for the invasive plant garlic mustard (Alliaria petiolata) within Ontario Natural Areas. V1.0. NCC – Southwestern Ontario Region, London, Ontario. 16 pp.

Nuzzo, V. 1997. Alliaria petiolata. Exotic Pests of Eastern Forests, Conference Proceedings, April 8-10, 1997, Nashville, Tenn.

What is a Weed Ninja?

Invasive plants are the vegetative evil doers of the plant world. They slyly sneak in and wreak havoc on unsuspecting native plant colonies, displacing, damaging or downright killing our local flora. Such plants are also difficult to control or eradicate – this is the difference between the aggressive invader and a regular non-native plant.

Pesticides work for some invasive plants, and biological controls are researched for others – but the harsh truth is that sometimes the most effective, and only, plant control strategy is manual removal and monitoring. Considering the amount of natural green areas we have in Canada and even naturalised spaces in Ottawa, this equates to the need of an ARMY of weed pullers.

However, since we can’t always work together, even if you pull a garbage bag of weeds alone you are making a difference. Imagine if everyone did that! You are the Weed Ninja who clears the greenspace of Garlic Mustard along your favourite jogging path. A Weed Ninja identifies Dog-Strangling Vine in their child’s playground and eradicates it. When you brush off your dog between runs in natural areas to prevent the transport of weed seed, you are making a difference. You are the Weed Ninja when you educate your neighbours and encourage them to not throw their Periwinkle or Creeping Jenny over the fence.

You are that stealthy force for good, so arm yourself with education, garbage bags and gardening gloves, then go out and HI-YA the heck out of invasive plants!

Join us for a Weed Bee this summer to pitch in as part of the group, or organise your friends and tackle forgotten public lands further afield.

Weed Ninjas Unite! Your Target: Garlic Mustard

Garlic Mustard

This is the perfect time of year to tackle our first invasive foe of the season: Garlic Mustard (Alliaria petiolata). If you’re gazing out the window along the Transitway or parkways, you can’t miss this white-flowered plant standing out from the grass or other herbaceous plants around it. Rarely does one plant grow alone, so also noteworthy is its nature of having one tall plant in the middle surrounded by many of its smaller brethren (or children!) This group growth form is due to the way Garlic Mustard produces many seeds, which it then releases in the same location.

Garlic Mustard is a shade-tolerant biennial plant that thrives in woodland settings. It is considered a serious invasive pest of natural areas, particularly woodlands, displacing native flora and severely reducing species diversity. Its aggressive, rapid growth allows it to form dense carpets that prohibit growth of other species.

Recent research shows that Garlic Mustard can release chemicals that destroy the mycorrhizal fungi that many trees depend on for nutrients. This allelopathy means that when Garlic Mustard invades a site, growth of tree seedlings is reduced. Maple trees are particularly susceptible. Like many non-native plants, Garlic Mustard has few natural enemies to help keep it in check.

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