2006-04-27 / News

Use mulch to save water, control weeds

By Roger Marshall

Given that we've had a very dry spring and are likely to have a dry summer, its time to be looking at mulches. There are many kinds. For example, some mulches can be used to prevent weed growth, some to conserve moisture, others can enhance plant growth or build soil.

Using mulch to

inhibit weeds

It has been calculated that a circle of bare soil 6 inches in diameter contains more than a million seeds and most of those seeds will try to germinate. If you leave soil bare, you won't stop weeds entirely, but you'll sure cut down on them if you use a mulch on bare soil. Around shrubs and plantings you should use a mulch of shredded bark or shredded wood. Make the mulch at least 2 inches deep with up to 4 inches being okay. Don't pile the mulch against tree trunks or you could start rot in the trunk. Instead mound it away from the trunk.

Shredded pine bark tends to be a little acidic so it should be used around rhododendrons and other plants that like acidic soil. If you plan on growing clematis, don't use pine bark mulch, its way too acidic, instead you might want to use 3/8inch rocks or small pebbles. Clematis is one of the plants that love alkaline soil. If you intend on mulching your vegetable or flower garden don't use pine bark either, it will make your soil acidic and slow the growth of your vegetables or flowers. In these gardens, you might want to use ground leaves or better yet, ground leaves and unsprayed lawn clippings. Leaves have a lot of carbon in them and lawn clippings have a lot of nitrogen in them. As the leaves will need nitrogen to break down, they can get it from the lawn clippings rather than pulling it from the garden soil.

You might also want to use one of the plastic mulches to inhibit weed growth. I have heard that red plastic mulch helps to promote the growth of tomatoes and peppers, so you might want to put it around your plants. I'm not a fan of plastic mulches unless they are covered with pine bark or stones to hide its ugliness.

Using mulch to conserve water If you want to conserve water, a 3to 4-inch mulch of untreated grass clippings on your garden will help keep the soil moist. You can also use wheat straw. Try not to use hay, because of all the seeds in a bale of hay. I once put hay down and spent years trying to get rid of all the weeds. At the end of the season, leave the mulch in place to help prevent nutrients from being washed out of the soil. You can apply more mulch the following year or simply dig in the old. I prefer not to walk on the garden beds and simply leave the mulch in place.

Any plants that shade the soil will also help to keep the soil moist. If you have ever harvested a lettuce or cabbage, you may have noticed that the area under the leaves shelters slugs and snails that love the dampness of being sheltered from direct sun. You can also use good quality compost as a mulch, too. Simply lay it over the growing bed and let it rot in. At the end of the season, simply dig the mulch into the bed.

Using mulch

for ornamentation

In Europe, people who grow alpine plants often use a thick layer of stones as a mulch and for good drainage. You can use this effect to enhance your garden, too. Many garden stores sell bags of colored stones that can be laid down to provide a pleasing effect if you like that style of gardening. I once saw a gardener who had used various colored stones to make a stone garden in the shape of his country's flag. While this suited him, and gave him no work once the job was done, a stone mulch can preserve moisture in the underlying ground and give good drainage through the stone.

Mulch for plant growth

If you want to conserve moisture and get your vegetables to grow, a mulch is an ideal way to do it. But you'll need to remember that mulches, as they rot, absorb nitrogen from the soil. So when you put a mulch down, sprinkle a little bonemeal down and rake it in before you throw the mulch over the top. That will give your soil a nitrogen boost.

Where to get mulch

Having just moved two truck loads of bark mulch, I figure that by now I am becoming an authority on it. If you only need a little mulch to cover a few feet, you can buy bags at garden centers or Jamestown Hardware can order it for you. I have been known to buy up to 30 bags this way, but it gets expensive in a hurry. I figure that buying by the bag is about 20 percent more expensive than buying by the truckload, and then you have to get rid of all those bags! If you need a truckload or a few cubic yards, Dave Ruggieri, 294-4032, over in North Kingstown has a huge pile. His special ground mulch is slightly less expensive, but pine bark mulch lasts a little longer.

How to estimate your needs

To estimate how much mulch you need, figure out the area that you want to cover. Lets say it will be a patch 10 feet by 9 feet, that's 90 square feet. If you lay the mulch about 4 inches deep, that works out to be 30 cubic feet of mulch. Divide the cubic footage by 27 to figure out how many yards of mulch you need. In this case, we'd need just over one yard of mulch. I'd get that in bags from a garden center. It will be easier to move and to spread. If you are like me and need to cover about 900 square feet, have it delivered by truck.

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