In the Garden:
In a few short months mugwort took over this perennial bed, crowding out the variegated phlox.
Mother Nature doesn't like to leave her soil bare and vulnerable to the elements, so she covers it with plants. Although the image is one of nurturance and protection, in my garden she has chosen to cover her soil with a very invasive and tenacious perennial weed called mugwort.
Weeds: Annual or Perennial?
You might know mugwort (Artemisia vulgaris) as an aromatic medicinal herb, and I, too, thought this way until I saw how quickly the plant spreads. The leaves resemble chrysanthemum leaves -- so much so that mugwort is sometimes called wild chrysanthemum. Indeed the plants do look like mums gone bad when they consume a perennial bed.
I identified the plant a few weeks ago with the help of a local herb grower. I thought I was dealing with annual ragweed, which, although it has its own drawbacks allergy-wise, isn't perennial and so will die back with the frost. Although ragweed and mugwort leaves are similar, this farmer advised me too pull up a plant and look for fat, white, runner roots, which would indicate I was dealing with perennial mugwort. I went out that evening, and even in the fading light the thick, white (and now ominous) roots were unmistakable.
These thick roots show how mugwort is able to take over a newly tilled bed so quickly. Tilling breaks up the roots into little chunks, each of which can sprout into a new plant. So repeated tilling won't control it. This is a perfect example of why it is important to identify weeds -- and all garden pests -- so you can plan appropriate control strategies.
Controlling Perennial Weeds
Annual weeds, such as ragweed and lamb's-quarters, can be controlled by diligently pulling seedlings throughout the growing season. Perennial weeds, such as mugwort and dandelions, tend to have larger, more far-ranging root systems that are difficult to pull, and root pieces left in the soil will sprout to form new plants. Tilling a bed filled with perennial weeds is akin to sowing seeds -- all those chopped-up roots are planted by the action of the tiller tines.
So how can you control perennial weeds? One option is to smother them. A heavy tarp or black plastic laid over garden beds for several months will suffocate the weeds. While this is helpful for vegetable and annual flower gardens, it does mean that the garden is out of commission during that time. In plantings of perennials, landscape fabric placed between the plants will help somewhat, but in my experience landscape fabric covered by a 3-inch-thick layer of mulch was not sufficient to control mugwort. I plan to transplant my perennials to a temporary garden, then cover the perennial bed with black plastic.
Another control strategy is cover cropping. By competing with weeds for light, water and space, fast-growing cover crops can help crowd out weeds. Several weeks ago I tilled my largest gardens and planted a mix of barley and Austrian peas. These cool-season crops will continue to grow into fall and again early next spring, hopefully helping to crowd out the mugwort. Later in the spring, when I mow and till under the cover crop residue, I'll add valuable organic matter to my silty clay soil.
It's frustrating to deal with a weed that appears almost malicious in its intent to take over. To put things in perspective, I did a Web search on mugwort and came up with these tidbits. I can't vouch for their accuracy, but they did make me smile!
--Mugwort has historically been used to treat chronic gastritis.
--In the middle ages in England, young women were told to place mugwort under their pillows to induce vivid dreams.
--A protective amulet made by sewing a small pouch from purple velvet and filling it with dried mugwort will protect the wearer against all sorts of bad external influences.
--Mugwort will help those of us who are considered "spacey" to become more "grounded."
--Rub fresh mugwort on crystal balls and magic mirrors to increase their strength.
Somehow, the plant doesn't seem quite so evil now!
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