Archive for Saturday, April 7, 2018

Garden Variety: Now’s the time to start weed control

April 7, 2018

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Gardeners like to keep weeds — the riffraff of the plant world — out of their landscapes and gardens to better allow their favored plants to thrive. Managing weeds is a challenging task, especially as cool weather-loving species are already arriving, and they always seem to grow faster and more plentiful than more desirable plants. The key is to use a multifaceted approach and get started now as the plants arrive.

The first step to weed control is deciding what a weed is to you and what your tolerance levels are for it. That might sound odd, but really, if you like to leave a few dandelions growing to add to your salad, then a dandelion is a desirable plant at your place. On the other side of it, if you planted old-fashioned cleome 10 years ago and it keeps coming up from seed, these volunteer plants may seem very undesirable to you. Once you have identified your enemies and the ones who only get annoying in bunches, move forward with control and eradication.

Mechanical removal is the cheapest and easiest means of getting rid of weeds. Pull them, use a trowel, garden knife or shovel to pop them out of the ground, or use a hoe to cut the tops away from the roots. Pulling or digging gets rid of each individual weed and can feel oddly gratifying — especially as you watch the plants wilt and die as their roots dry out in the sun. Hoeing kills some weeds, but the toughest will come back from the roots. Still, it is a good option when you have a lot of ground to cover or the soil is hard and dry, making it hard to pull weeds out of the ground.

Speaking of weeds being hard to dig: The best time to pull or dig them is after a rain or irrigation while the soil still has moisture. If the soil is too dry, they will just break off and you’ll spend a lot more time and energy trying to get rid of them.

The bad part about any kind of mechanical removal is that it disturbs the soil and/or mulch and turns up new weed seeds. Weed seeds need light and moisture to germinate. If they are buried very deep in the soil they will eventually lose viability, but the most frustrating can hang out in your garden for decades waiting to be brought up to the surface. Mulching over the disturbed soil areas can help, as well as avoiding excess tillage and cultivation.

Mulch blocks light from weed seeds (preventing germination of at least a few), minimizes soil and moisture fluctuations in the soil, and breaks down to improve soil. In the landscape, wood or bark chips are the best option. In the vegetable garden, straw or prairie hay work best. Compost, chopped leaves, pine needles and other plant waste materials can also be used. Plastic and rock can also be used as mulch and will prevent some weed growth, but they lack the other benefits of mulch derived from plant materials.

Filling in those empty spaces in the landscape leaves less room for unwanted plants to grow, so look at places to fill in this spring. Large expanses of mulch are better than large expanses of bare soil, but often fill in with weeds due to the lack of competition. In the vegetable garden, consider planting in blocks instead of rows, or find other ways to group plants and minimize bare space.

If weeds get away from you at some point this season, the best thing you can do is try to remove the seed heads before they release hundreds more seeds into the landscape. Clip them with shears or a scythe if you happen to have one, or use a string trimmer to lop off the tops. Then you can mechanically remove the rest of the plants later.

One thing some gardeners try that sounds like an easy fix to weed problems is weed mat or weed cloth. Weed mat is usually black, looks like a heavy-duty fabric or felt and is sold in rolls. Weed mat is a fantastic product to use under stonework such as a flagstone patio, brick walkway or pebbled path. In the landscape it works OK the first couple of years, but if mulch is used on top of it, weeds will end up germinating in the mulch and root down into the fabric, making them harder to remove. Weed mat also restricts the movement of air and water to plant roots, so it is not recommended for use in close proximity to desirable plants.

— Jennifer Smith is a former horticulture extension agent for K-State Research and Extension and horticulturist for Lawrence Parks and Recreation.

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