Weed Control Strategies

Learn To Love Your Weeds

No matter how hot, how dry, how wet, how cold–indeed, whatever the weather, the weeds seem to love it. The benign maritime Northwest is a generous host to many an unwanted import that makes itself all too much at home here. In years when gardens struggle and crops fail, weeds thrive. What’s a gardener to do?

One solution is to learn to love weeds. Dandelions are quite lovely in a meadow and pink and white English daisies and blue veronica are charming in lawns. Red and copper clovers make handsome accents in beds and borders and help store nitrogen in the soil. Dock has beautiful architectural seedheads and great fall color and its summer leaves look as good as many hostas. Thistle seed nourishes goldfinches, while morning glory and stinging nettles feed butterflies and other pollinators.

Or Not

No? Another solution is to develop strategies that give you an edge over the worst weeds. For instance, among the least favorite lawn weeds, those ubiquitous dandelions rank pretty high. Professional dandelion growers (fancy salad mixes sometimes include them) say their worst crop enemy is turf grass. Thus, to get rid of dandelions, grow stronger grass.

How? Most turf has shallow, weak roots, largely because it is overwatered. To win the war against lawn weeds, start with a step-weeder. These clever gadgets pop tap-rooted weeds out of the ground with a quick press of the foot (notice that you don’t need to bend over). This trick works especially well in winter, spring, and fall when the soil is damp and loose.

Autumn is the perfect time for the next step comes this fall; spread up to an inch of compost on the lawn and overseed with a regionally appropriate turf mixture. A rugged playground mix is great where there’s lots of foot traffic, while shade tolerant blends work best i areas that get less than a full day of direct sun.

Mow Mow Mow

In the meantime, mow weekly as long as your grass is actively growing. Frequent mowing will reduce or eliminate coarse wild grasses and many broadleaved weeds in a few seasons, because mowing favors fine textured plants that are more resilient to being cut down or browsed.

Sweep Scotch Broom Clean Away

Scotch broom is an easy one; pull youngsters in the rainy season when the ground is soft. Old growth Scotch broom won’t come back when cut, so chop it off at ground level, leaving the roots and nitrogen storage nodules in the soil. Spread mulch after removing Scotch broom because it throws an amazing amount of seed around.

The Self-Igniting Weed

One precaution; never heap Scotch broom and leave it because it may self-ignite in warm weather. That’s because this sturdy plant contains volatile oils that can heat up fast in the sun. To take advantage of this, grind Scotch broom stems and roots and add them to the compost heap to heat it up. Leave out the seedpods if possible, though a well constructed pile can get hot enough to cook the seeds.

Controlling tap-rooted weeds like thistles is a harder job. Canadian thistle, with fine textured leaves, is (relatively) easier to get rid of than Scotch thistle, which seems to put down roots to China. Weeds with running roots, like bindweed, are also tough to eliminate because any scrap of root left behind will resprout.  In each case, frequent mowing can keep the plants from going to seed and will weaken the root system over time. However, well established weeds may need several types of intervention.

Three Steps To Success

For persistent pests, try three highly successful techniques:

Use your step weeder whenever you spot a fresh crown of Queen Anne’s lace, dandelions, dock, thistles, and other tap-rooted weeds. The weed may well come back a bit, but frequent removal really speeds up the root-weakening process.

Cut crowns back to the root in spring and cover the cut part with high-nitrogen fertilizer. Try this with pretty much everything from thistles and bindweed to blackberries and false bamboo. This may kill small plants outright.

With larger plants, this will trigger renewed growth that is “paid for” by the mother root. New growth should be cut as soon as it matures and begins to replenish the root (the texture changes from soft and fresh to matte and tough). Repeated cutting and fertilizing will eventually exhaust the storage root.

Cut weed stems short in spring and paint each stem with an herbicide concentrate such as Burnout (a citrus and vinegar based product). From mid-April into May, plant are in intake mode and will carry the toxin to the root. Hand paint the herbicide concentrate just on the cut stem. This can also work with blackberries and false bamboo.

Get With A Program

To keep weeds from taking over, we need to follow a consistent program of controls. Where Himalayan or European cut-leaf blackberries are thick, mowing 3-4 times a year will eliminate them within a few seasons. If you don’t have time to do this or you’ve got lots of property to cover, timing your cuts can maximize the effectiveness of this technique.

In spring, allow young plants to send up shoots (these will feed off and deplete the mother root). As soon as the leaves turn matte and dark green, they become capable of photosynthesis and can replenish the root. That is the moment to make your first cut, clear to the ground (usually in May).

Let a fresh crop of shoots develop and again wait until they turn matte and dark green before making your second cut (usually In August or September). Do it right now if you haven’t cut your blackberries back this year. Onward!