Wednesday, April 6, 2011

Horsetail Weed つくし

Horsetail weed (Equinestum) seems to be a problem for many people, as my post about horsetails way back in 2009 is still the most viewed post of the blog.  So here is a little bit more information for those poor souls struggling with horsetail weeds.

Field horsetail has two types of hollow stems which grow from deep, creeping rootsocks.  The leafless or fertile stems are about one foot high (130cm) with a spore bearing cone at the top.  These emerge in early spring and die back soon after the spores are shed.  The sterile stems, two feet high (260cm), produce whorles of green leaf-like branches which die back by winter. Unfortunately, the rootstocks do not die back. The plants are maintained by small tubers that store food reserves and an extensive creeping rhizome system that penetrates to great depth in the soil. (From British Columbia's Ministry of Agriculture)

According to University of Wisconsin's Weed Science Department, horsetail is typically found in wet or acidic soils (that's us here in the Pacific NW), it is more productive in full sunlight, and its growth is significantly supressed by the shade of taller plants.

In Japan, the slender shoots of horsetail are the first delicacy of Spring and school children sing songs and draw cute little animated pictures of "tsukushi". When we moved to the States, I was astounded at the abundance of horsetail growing near my mom's rented farmhouse.  I took my children and gathered an armful, brought them back to the house and cooked them up.  Ick.  They were most definitely NOT the same variety of horsetail as the tender "tsukushi" we had collected at our previous home.

How to get rid of these tenacious weeds?  First, think non-chemical.  Horsetail weeds produce spores, but their main mode of reproduction is by their rhizomes.  If a rhizome is broken off from the main rhizome, it will start it's own root system. Undisturbed rhizomes usually don't bother to reproduce. So, DON'T DISTURB THE ROOTS.  Cut or burn the stems when they appear. Mow over them if you can. Fertilize and lime the soil (horestail does not respond to nitrogen). Plant grass that will choke them out. Plant tall plants in a patch of horsetails--that will both choke them and deprive them of sunshine.

If you have a large patch of horsetail, you can cover it with black plastic (put rocks on the plastic to hold it down), and it will suffocate and die in a year or two.  Heavy cardboard and straw will do the same, but it will need to be replaced as it decomposes. Sawdust and bark are ineffective.

If you are desperate and must have chemicals, you may be disappointed. Most herbicides have been found to be ineffective on horsetail. Round-up does not work. Triclopyr and glyphosate are ineffective. 2, 4-D is only partially effective. Dichlobenil is effective when applied mid-winter, before the stems emerge.  Washington State University has a more detailed article on herbicides here.  Be sure and READ THE LABEL of any herbicide or pesticide before using and only apply to the plants and sites listed.

Horsetail is also a powerful herb, containing silicic acid, calcium, potassium and aluminum salts. Historically, horsetail has been used to stop bleeding, repair broken bones and as an herbal remedy for arthritis.  There are many side effects if taken incorrectly, however, so you will need to consult with a qualified herbalist before using.






つくしは強いハーブです。ケイ酸、カルシウム、カリウムやアルミニウム塩が入っています。むかしは止血剤、骨折やリウマチの治療薬としてつくしを使いました。 Pin It

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