invasive plants in gardens

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Author Message

miyo stevens

I'm looking for some direction that will lead me to information about what soils amendments are needed to dissuade invasive plants from taking up residence in my large garden - invasive plants such as Canadian Thistle, Tansy Ragwort, Wild mustard, Bog Rush, Bull Thistle, and Dock. Also what do they take out of the soil? Like thistle, I know that thistle are healthy food for sheep, cows and horses and they'll eat them when they've wilted. Someone once said that thistles are more nutritious than the grasses stock are usually left to munch on. Perhaps it is good to compost them minus the roots and the seeds. Lots of work though! The question is - What can invasive weeds tell me about my soil and how can I best deal with them other than pulling them year after year while trying to avoid their seeding on this side of the fence?

Monday 15 August 2011 10:33:42 am

EJ Hurst

Yes, I would also like to know about Gout weed which is taking over my parts garden. Pulling it up just makes 10 more new plants for each piece.

Monday 15 August 2011 12:52:13 pm

Linda Gilkeson

The invasive plants you both list are difficult to control, no question. There really is no amendment that will help keep them out because by their nature they are well adapted to grow vigorously in a wide variety of sites.
Where it is feasible for your situation, the best control for invasive plants is a thick, light-proof cover over the soil where the problem plants are growing. Mow tall plants to the ground, then lay down a thick layer of newspapers or cardboard or even a heavy opaque tarp. Paper and cardboard are better as they don't have to be removed later and they add organic matter as they break down. Covering the newspaper or cardboard with a layer of leaves, bark, etc. will make it look presentable while you are suffocating the weeds. Leave the cover on the soil as long as you can but not less than 3 months--over the whole winter is great.
If you can't do this, then being very persistent in pulling out the weeds as soon as they get large enough to identify works better than pulling them when they are quite large and have built up a food supply in the roots. I find that one season of being right on top of a particular invasive, especially those darn 'ground-covers' that get away, is enough to knock them out of my garden. But you do have to be very vigilant for that season.
No matter what methods you use, you need to remember that there are still weed seeds in your soil. They will continue to germinate whenever you disturb the soil. So you have to keep up your vigilance for the first couple of years until the seed supply in the soil is depleted. Be sure to cut down nearby weedy areas before they go to seed to prevent new seeds from arriving in your yard and avoid weed seedy materials (such as spoiled hay). Keeping deep mulches of leaves, straw, etc. around plants, whether in ornamental or food gardens, smothers new weeds as they germinate and by exluding light prevents some seeds from germinating at all.
After the first few years of hyper-vigilance and mulching you will notice that there are very few new weeds showing up--and gardening gets much easier. Honest!

Friday 19 August 2011 08:19:17 am