Don Janssen: Mulch garden to stop weeds, conserve moisture

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Maybe you can’t fool Mother Nature — but you can imitate her.

Think of a pine forest, carpeted in fallen pine needles. Or a stand of hardwoods and the fallen leaves that muffle and cushion your footsteps.

In the forest, this layer of organic materials is called duff. In the garden and landscape, it’s mulch. The major difference is that mulch doesn’t just happen in the garden — you have to put it there.

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For reliable, research-based information 24 hours a day, seven days a week, contact the UNL Extension in Lancaster County Web site at lancaster.unl.edu. It is continually updated with information. Features for today are:

-- What’s the Scoop on Insect Repellents?

-- Keeping Kids Safe Online

-- 9 “Bites” for Better Tasting Fruits and Veggies

-- During Dry Spells, Don’t Forget Your Woody Ornamentals

-- Safeguarding Your Health and Nebraska’s Livestock

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Five Things To Do This Week

1. Order spring-flowering bulbs for fall planting.

2. Check trees and shrubs for girdling damage by guy wires, burlap or ropes.

3. Don’t fertilize woody plants now.

4. Keep newly established plants well-watered.

5. Keep the garden well-watered during dry weather.

Gardeners can use both organic and inorganic materials for mulch. Both have their pros and cons.

Gardeners usually use mulch to inhibit weed growth and conserve soil moisture. Mulch prevents weed growth by cutting off light to the soil. It conserves soil moisture by slowing the evaporation of water from the soil. As a result, plants are less likely to be stressed by dry weather and need watering less often.

Organic mulches can be tilled into the soil at the end of the gardening season. As they decompose, they add organic matter to the soil, improve soil structure and release nutrients. Inorganic mulches, such as black plastic, are not biodegradable and must be taken up at the end of the gardening season.

The best mulch for any particular gardening situation depends on the crop and the objective.

Early in the season, you can use plastic mulch to warm the soil so that early-planted seeds and transplants get off to a quick start. Clear plastic will heat the soil as well as black plastic, but it doesn’t control weeds the way black plastic does because it lets the sunlight through to emerging weed seedlings.

An organic mulch spread after plants are in or seeds have germinated or over plastic through which crops are planted will keep weeds from staging a garden takeover.

Mulching for weed control is most successful against small annual weeds. For best control, mulch before weeds emerge.

Mulches aren’t as successful in controlling quackgrass and other perennial grasses. They may work their way up through even several inches of organic mulch. Black plastic may control them by cutting off the light they need to produce food. The heat and moisture that build up under plastic in hot weather also may help kill the weeds.

By keeping the soil moist and cool, organic mulches also can make a slug problem worse by providing a cool, damp place for them to hide during the heat of the day. Putting slug baits under the mulch may give some control.

On heavy clay soils, plastic mulch, especially, may hold water in too well. Plants may suffer from having too much water and not enough air around their roots. To prevent this waterlogging, apply only organic mulches. You also can build raised beds and apply mulch over them to avoid waterlogging.

On the plus side, mulches keep the fruits of melons, cucumbers, tomatoes, strawberries and other crops off the ground and free of mud spatters and, therefore, free of ground stains and rots. Using organic mulch around vining crops such as squash and melons eliminates the need to cultivate around them to control weeds. As these crops sprawl, this becomes all but impossible.

How much mulch is enough? Three or four inches of organic mulch or one thickness of 1½ mil plastic will do the job. Around low-growing crops such as lettuce and radishes, 1½ to 2 inches of organic mulch is the maximum. Around taller plants, start with an inch when they’re seedlings or freshly set transplants and increase it to at least 3 inches as they grow taller.

Don Janssen is an Extension educator with the Lancaster County Extension of the University of Nebraska-Lincoln. He can be contacted by telephone at (402) 441-7180; by mail at 444 Cherrycreek Road, Lincoln, NE 68528; or by e-mail at djanssen2@unl.edu.