August 22, 2015

1 - Moist soil and mulch make weed removal easier in the garden.

Yard and Garden August 22, 2015

Q.

I am having a hard time controlling weeds in my garden. I do not like to use weed killers in the garden, so I pull the weeds by hand, but they just break off and come back within a few days. Is there some way to get rid of the weeds without weed killer?

A.

When soil is dry it may hold plant roots tightly causing the weed to break off and then regrow as you have described. Weeds are much more easily removed from moist to even soggy soil immediately after irrigating. For some weeds this is effective even when the weeds are very close to the desirable plants. Some weeds have a more fibrous root system and may pull us much soil at the base of desirable plants, or even dislodge the desirable plant when pulled. In that case a knife or other tool to carefully cut the roots just below the soil line or below the crown of a grassy weed may allow you to manually remove the weed while doing minimal damage to the desired plant.

Further away from your garden plants you can use a hoe to manually remove the weeds. I like to use a scuffle hoe that cuts the weeds roots just below the soil line. The weed can then be raked from the garden. A scuffle hoe disturbs the soil less than a chopping action type hoe which disturbs the soil and brings new weed seeds to the surface where they can sprout and perpetuate the weed problems.

Another way to minimize weed problems is to use mulch to cover the soil and reduce weed growth. Some gardeners use black plastic under their plants. The black plastic eliminates sunlight needed for germination of weed seeds, but it can become hot enough in New Mexico's sunlight to burn the garden plants. A covering of organic mulch may help avoid overheating. The organic mulch (straw, wood chips, newspaper, or other biodegradable material) may be used without the plastic as well. A thick layer will also exclude light and reduce weed seed germination. Perennial weeds may still come through the mulch since they do not need light to germinate, but the mulch will help maintain soil moisture making the weeds easier to pull. Organic mulches also moderate soil temperature changes and may protect plants from our intense summer heat. The soil in direct sunlight can be 10 to 20, or more degrees, hotter than the surrounding air.

Weeds you have pulled can be composted to use as soil amendment in the garden next year if they are not diseased or have not produced seeds. If your compost pile heats properly the weed and disease concerns become lessened. Another way to be sure weed seeds do not germinate next year is to put the weeds into a black plastic bag in a sunny location for a few days before putting them into the compost. The weeds should be freshly pulled so that they are still moist when you do this. They heat of the sun will kill most of the weed seeds and potential plant diseases in a few days in the solar heated plastic bag. There should then be less concern about perpetuating the weeds with the compost next year.

If you eventually become so frustrated with the weeds that you decide to use chemicals, be sure to choose a product labeled for use around the desirable plants you are growing and then read, understand, and follow the directions.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook page.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!