Ambrosia artemisiifolia: delcious-sounding name for a very annoying plant

Warning: this plant is considered a noxious weed under the Ontario Weed Control Act.

Such a lovely-sounding name for this plant with such pretty, fern-like leaves! (click the photo to get a better look) If only it weren't for the flowers...

In case you haven't recognized this common but easily overlooked plant yet, it's better known as common ragweed (petite herbe à poux). Those boring little green flowers have no interest for animal pollinators, so ragweed instead releases massive amounts of lightweight pollen into the wind, relying on the sheer quanitity of pollen to ensure that some of it will reach a female flower and fertilize it. (Separate male and female flowers are produced on each plant.)

Ragweed grows in the same habitats and blooms around the same time as its showier cousins, the goldenrods (verge d'or, Solidago spp.). Because ragweed is so inconspicuous, goldenrod is often unfairly blamed for ragweed pollen allergies. In fact goldenrod pollen is too heavy to be wind-borned; that's why it has those gorgeous flowers, to attract the insects needed for pollination.

According to Wikipedia, the genus name Ambrosia comes from the same root, άμβροτος, as the ambrosia which is the food of the gods, but this root word actually means "immortal", referring to the difficulty of eradicating this plant. (This species is actually an annual, so not immortal by any means.)

Ragweed is one of the top 10 herbacious plants to feed wild birds, because it produces numerous, oil-rich seeds. However, given how many people are allergic to it, I think it should be kept to wilderness areas far from humanity, certainly not in Toronto gardens.

Asclepias syriaca

Note: this plant is legally considered a noxious weed in Ontario (but grow it anyway).

Asclepias syriaca, known in English as "common milkweed", "butterfly flower", "silkweed", "silky swallow-wort", or "Virginia silkweed", and in French as asclépiade commune, bébé lala de lait, herbe à ouate, or herbe aux perruches, is a perennial native to eastern and central North America. The "milk" in milkweed is its thick white sap, which is poisonous to many animals. Some insects, most famously the monarch butterfly larva, are able to feed on milkweed. Monarchs store the toxins in their bodies as a deterrent to predators.

The field behind my mom's apartment buidling in Almonte (eastern Ontario) is dominated by various non-native flowers, but the milkweed is one native that is holding its own. When I checked the undersides of the leaves on this vigorous clump, I found many eggs, probably monarchs. You can see how a big group of milkweed like this would be a butterfly magnet!

The clusters of muted pink flowers are attractive to many different pollinators.

Now, technically, this milkweed is considered a noxious weed under the Ontario Weed Control Act. (Asclepias viridiflora, Asclepias incarnata, and Asclepias verticillata are also listed as noxious.) Milkweed is toxic to livestock and can also invade fields of crops, reducing their yield, so if you are farming or live near a farm you'll want to control or remove milkweed. But I don't think that applies to most of us here in Toronto.

The asclepias are a vital genus of plants for monarch butterflies; they are the only plants that their larvae can eat. If milkweeds are eliminated everywhere, then so to will be the monarch butterflies. So I think that those of us who aren't near farms should make an effort to include some of the asclepias in our gardens if growing conditions are suitable.

The Ontario Weeds Act FAQ states:

As long as the population of milkweed planted doesn't negatively affect agricultural or horticultual land by spreading seed and new vegetative plant material (i.e. root stock) into fields, nurseries or greenhouses then it is acceptable to plant milkweed in your garden. It is recommended that you consult with your local weed inspector and/or neighbours so that all parties involved are comfortable that the impact to agriculture or horticulture is negligible.

Tragopogon dubius seed heads

Warning: this plant is considered a noxious weed in Ontario Tragopogon dubius, known in English as "western goatsbeard", "yellow goatsbeard", "meadow goatsbeard", "western salsify", "common salsify", or "wild oyster plant", and in French as salsifis majeur or salsifis douteux, is a biennial native to Europe. The flowers and seedheads are somewhat similar to those of the dandelion, but goatsbeard is much larger and the leaves are grass-like and clasp the stem.

Goatsbeard is considered a noxious weed under the Ontario Weed Control Act.

I photographed this plant in Almonte, in eastern Ontario.

Toxicodendron radicans foliage

Warning: this is a noxious weed in Ontario. Toxicodendron radicans, known in English as "poison ivy" and in French as sumac grimpant, herbe à puce, bois de chien, or sumac vénéneux, is a woody vine native to much of North America. It's important to be able to recognize its characteristic leaves, with three leaflets, because it contains urushiol, an oil which causes a horrible itchy rash in many people. (When we were kids, my sister actually decided to try rubbing it on her arm to see if she really would get a rash. She sure regretted that.) Because of its allergenic properties for humans, poison ivy is considered a noxious weed in Ontario.

Although few people will deliberately plant poison ivy, it is one of the top twenty plants in terms of providing food for birds and mammals according to American Wildlife & Plants: A Guide to Wildlife Food Habits by Alexander C. Martin, Herbert S. Zime, and Arnold L. Nelson (New York: Dover, 1961). I like Sara Stein's suggestion, in Noah's Garden, of planting poison ivy in areas where vandalism is a problem; it would not only deter vandals but feed birds as well.

I photographed this poison ivy in Purdon Conservation Area.

Ambrosia artemisiifolia: foliage

Note: this plant is considered a noxious weed under the Ontario Weed Control Act Ambrosia artemisiifolia, known in English as "common ragweed" or "short ragweed" and in French as petite herbe à poux or ambrosie à feuilles d'armoise is an annual native to North America, infamous for its highly allergenic pollen.

Last year when these pretty leaves started emerging in the spring, I was sure they were something "good". Imagine my disappointment when I realised they were in fact ragweed. Ragweed's flowers are tiny and green; they don't need to be showy to attract insects because they are wind-pollinated. I don't know if I'm allergic to ragweed myself (I'm stuffed up all year round due to my fibromyalgia), but a friend down the street suffered from ragweed allergies, and ragweed pollen can travel hundreds of miles on the wind.

Even though ragweed is a native plant, I think those of us in populated areas should pull it out of consideration for all the people sickened by ragweed pollen. The Ontario government has designated ragweed as a noxious weed.