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alternatives to pesticides - weeds - Poison oak

poison oak

Poison Oak

In the open or in filtered sun, poison oak grows as a dense leafy shrub. Where shaded, it becomes a climbing vine. Its leaves are divided into three leaflets. Poison ivy, which grows in eastern Washington, is very similar, but it is more sprawling in growth habit and rarely climbs. The foliage of both turns bright orange or scarlet in the fall.

Poison oak will eventually die out if you keep it clipped to within an inch or two of the ground with a power mower or hand clippers. Grasses tend to crowd it out so it can’t get enough height to put out leaves.

Physical Control

Woody perennials, such as poison oak and wild blackberries, have high reproductive capacities, and established plants are difficult to eradicate by digging. But it is not impossible. Mulching is the easiest way to get rid of stubborn perennial weeds, but it may take a year or two. Grub out rootstocks; treat with boiling water, mulch heavily. Mulch options include old carpeting, old swimming pool liner, and 10 to 20 sheets of weighted newspapers or sheet metal, such as old tin roofing. To eradicate young plants, put on a long-sleeved jacket and leather gloves and pull them out by hand as fast as they appear to destroy the roots.

Biological control
If the plant is young and not woody, goats, if managed properly, can be helpful in eliminating woodier weeds such as poison oak and ivy, wild blackberry, bamboo and scotch broom.

Least-toxic chemical control
If plants persist, paint the leaves with the least-toxic systemic herbicide available rather than spraying.


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