30 Aug 2010

Weeding – Field Bindweed – Non Chemical Methods of Weeding

bindweed - Convolvulus arvensis

[One person’s weed is another’s flower?- Bindweed flower, Convolvulus arvensis]

Bindweed can be  a pretty and probably harmless flower in fallow fields.  But, in my yard, it’s ugly, aggressive, out-of-place, detrimental; and, therefore a weed.

A weed is any plant that is growing in a place you don’t want.  To me, weeding is not about fighting mother nature (which is useless).  It’s more about opening space and resources for the plants you want to flourish.  You’re working with mother nature, not fighting her.

Little can flourish amidst too much competition and bindweed is the most competitive weeds I’ve encountered, so it must go.  It snakes through weed fabric, through inches of mulch.  It strangles small bushes and trees (why are there white trumpet flowers in the canopy of those evergreens?!).

If you’re not familiar with this weed, consider yourself fortunate.  It has dark green leaves the shape of arrow heads, and a small white or pink flower that resembles a morning glory.  It grows in heat, full sun, good soil, bad soil– even hard pan.  Why it’s tough: the roots can run deep (studies have found viable roots at 10-14 feet deep); and, the roots run both vertically and horizontally.  Because of this extensive root system it can persist and lie dormant for many years (some report up to 60 years).

Pull the Top Growth Every 2 Weeks

You will probably never completely get rid of it, but you can try to suppress it by vigilantly plucking the top growth.  This weed is tough to pull roots out with your hands because the top growth usually breaks away from the thin roots.  If you remove the leaves each time they re-sprout (about every couple of weeks), the plant will exhaust its energy  and eventually die; however, this process could take years.  This approach requires you to be consistent and vigilant– never let the weed develop more than five leaves, flower, or go to seed.

Cultivate

Because I don’t use herbicides, I have few options but to remove the weed by digging it up.  Although it may have hellishly long roots, the bulk of the root system resides within the first two feet of soil.  Depending on the situation, generally, I dig out the roots until there are no more.  Since even fragments of roots are capable of generating regrowth, I go as deep and wide as possible without disturbing the roots of any nearby plants.  After removing as much roots as possible, I turn the soil, repair the weed fabric and apply a thick layer of mulch.  Several university studies conclude that vigilant, deep (16-18 inches) cultivation is the best approach.

Out-weed It (Out-compete it)

This is one of the least labor intensive methods.  The idea is to plant something with aggressive early spring growth– this will deprive the bindweed of light and water.  I planted Erigeron (“Fleabane”) and Lantana.  Be careful, these plants can be very invasive.  (It’s a compromise. )  Both have worked very well to keep bindweed at bay as long as they were not stressed and were healthy.  In places where water was insufficient, the bindweed won.

Soil Solarization

If you need to prepare raised beds where bindweed is or was growing, you could try solarizing, but most university studies have shown that this method is only marginally effective on bindweed because of its extensive dormant root system and hard seed coat.  Within weeks, the bindweed returns.  If the idea is to start with a clean slate of soil before starting a new planting bed, I think this is a good way to go.  This method involves preparing the soil in the hottest months of summer by removing all the weeds, by tilling, by amending, by leveling the soil and by thoroughly watering.  You then cover the area with 1-2 mil thick clear (not black) plastic.   You should leave the plastic in place, depriving the area of water and air, for at least 6 weeks.  Clear plastic and the moisture from the watering allows the soil to reach temperatures hot enough to kill off diseases, and the top growth of the bindweed, but it won’t necessarily challenge dormant seeds or deep roots. Be sure to choose the hottest part of the season and weigh down all the edges where wind or air might infiltrate.

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