Monday, May 6, 2013

Ochard Update - Entry 2: Invasive Plant Removal

Year in, year out, we battle the same old foes on the Orchard grounds: Invasive Weeds.  We had a recent workshop run by our community gardener Matt, who also works with an environmental firm.  Among the material handed out was this guide from the Greater Vancouver Invasive Plant Council.

Creeping buttercups have taken over large swaths of the Orchard land.  They like shady, poorly drained areas and spread quickly through areas, both by expanding roots, by disturbed rhizomes - when fragments of the plant roots are broken apart - and from seed.  Originally from Eurasia, these plants were introduced as ornamental groundcovers.  However, their vigourous spreading habit often shades out other plants, is toxic to grazing animals, and they deplete the soil of potassium.  Last fall, volunteers and I dug them out and planted clover seeds instead; the buttercup quickly re-established itself and smothered out the clover.  This year, we've attentively dug out the stragglers as they've re-emerged, and planted it with a mix of wildflower, clover, and mustard seeds  (which I got plenty from the local Indian grocer).

Post-dig buttercups re-emerging.  
The idea is that these new plants will hold the soil in place, keep the nutrients active, and prevent the buttercup from coming back in full force.  We've chosen plants that will be good companions to future fruit shrubs we will transplant into the area - clover (as with other peas) adds nitrogen to the soil, and the flowers from mustard will attract beneficial bugs while repelling pests.  As they grow, we need to ensure they are well-watered, especially with the early heat-wave we're experiencing.

Dug-up Morning Glory Roots

Morning Glory is another invasive that is even more problematic.  It is a bindweed that has generates long, climbing vines around trees and taller plants and can smother them by depriving them of sunlight.  Morning glory tends to grow in sandy It builds an extensive root system (albeit generally shallow) that can span meters upon meters, sending long, cable-like roots through entire sites.  And improper weeding can make the situation worse - morning glory can regenerate from small pieces left in the soil.

One method we've used to control its growth on site is by laying cardboard and piling mulch on top.  But year after year, it finds a way around and over the cardboard, sending roots through the decomposing mulch.  So, aside from pulling out cables, we also just tear out  the emerging vegetation, hopefully depriving the plant of sunlight (and food) without disturbing the soil too much.  But I've got an experiment soon on the go: apparently, large pumpkins and squash plants can help shade out bindweed, so these are going in next week and staying over to fall.  After the harvest, we will plant rye, as it is known to create allelopathic effects that discourages broadleaf plants, like morning glory, from establishing.  So we'll see if this strategy works!

Burdock (and my thumb for scale)
Burdock is an invasive plant that is also a food crop - its roots are harvested in Asian cuisine, and used to be popular in Europe.  The plant has a very deep, soft tap root, grows stalks and leaves not unlike rhubarb, and can get as large as 3 meters tall.  We had several last year that grew to about 4 feet.  Hacking it down was no fun process - its seedpods have burrs that act like velcro and stuck to my clothing.  I dragged them all over the house.  I've dug them out at every opportunity this year, but they keep coming back.  Their seeds remain viable for quite a long time.  I think I'll try to eat the next one I dig up - that may be the best strategy to keeping it in check :p  I'll let you know how it goes.

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