Washington State University Extension

Garden Tips

Archive for June 2015

Floating Row Covers in Gardens

GARDEN TIPS – written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA April 9, 2015

Because I am lucky enough to work with WSU Extension Master Gardeners I am privy to the tips and tricks they have for coaxing the most out of their gardens. One of these is the use of floating row covers.

Have you ever noticed a garden with the rows or beds covered with white fabric?  The material is called floating row fabric. It is called “floating” because it is a very light fabric made of spun bonded polypropylene or polyester. The fabric is porous enough to allow light, water, and air through. It also keeps out certain insect pests, such as beet and spinach leafminers and cabbage loopers.

Floating row covers also provide plants with some protection from wind (a big factor in our area). Plus, depending on their weight, they can help protect plants from light frost by trapping heat close to the plants.  Generally, there are three weights of row fabric, light, medium, and heavy.

Heavyweight fabrics only transmit 30 to 50 per cent of the light, but can protect plants from temperatures within the 24-28 degree range. They are used more as a “garden blanket” for frost protection early in the season and are not usually left on for an entire season.

Lightweight fabrics do not provide any protection from frost, but do transmit 90 per cent of the light. They can be left on the entire season for protection from insect pests, but are not left on if the crop, such as squash or cucumber, requires cross pollination by bees for fruit production.

Lightweight fabrics are not as durable as the other weights, have a tendency to rip, and will likely last for only one season or less. The medium weight fabrics last longer and are the best choice for home gardeners. They transmit 85 per cent of the light and provide frost protection down to 28 degrees. When treated with care, this weight an last for several years.

If you want to use floating row covers in your garden, the first step is to obtain the fabric. Floating row fabric comes in different widths and lengths. Fabric should be wide enough to cover the row or bed, provide enough “slack” to allow for the crop’s growth, and still have wide enough edges so they can be secured. WSU experts recommend using 6-foot wide fabric when covering a 3-foot wide row.

Next, plant the row and then place the fabric over the row. As you can imagine, something that “floats” is liable to blow away in a good breeze unless well secured. Next, trench around the four edges of the row or bed, place the fabric edges in the trench, and then refill it with soil. Leave the fabric loose enough so the plants can lift the fabric up as they grow. Instead of covering the edges with soil, some gardeners secure the edges with boards, making it easier to periodically check below the fabric for any problems.

Another approach is to create a row cover fabric tunnel by constructing a frame using wire or pvc pipe hoops and then attaching the fabric to the hoops with clips and securing it with boards at the base of the hoops.

You can find row cover fabrics at local garden stores or for sale on-line. Look for the size and weight that best meets your needs. Now you know one of the Master Gardeners’ tricks too.

For more information on installing a floating row cover, download the free WSU Extension fact sheet FS089E “How to Install a Floating Row Cover” available at

Helping Landscape and Garden Plants Cope with Drought

GARDEN TIPS – written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA

Written April 2, 2015

With the prospect of limited irrigation water in the coming months, we may have to make agonizing decisions regarding which plants in our yards and gardens to save and which plants to let go. To me, it is like making ASophie=s Choice.@  Before making these difficult decisions becomes a necessity, there are some things we can do to make the most of the water that will be available.

As much as 50 percent or more of the water that is applied to bare soil is lost to the atmosphere through evaporation from the soil. The rate of evaporation increases with increasing air temperatures, solar radiation, and wind. In addition, the lower the humidity, the faster the evaporation. By applying a mulch in our landscape and garden beds we can reduce the amount of soil moisture lost through evaporation by as much as 50 per cent, depending on the type of mulch.

For landscape plants and perennial flower beds, I recommend using shredded bark or wood chip mulches applied on top of bare soil and maintained at a depth of 3-4 inches. Bark and wood chip mulches should not be used in vegetable gardens and annual flower beds because they will become incorporated into the soil. This causes a problem because soil microbes will use the nitrogen in the soil for the decomposition process, thereby tying up the nitrogen and making it unavailable to garden plants.

Where annual crops are grown and the soil is regularly tilled or disturbed, organic mulches that break down more quickly are advisable. I recommend applying well-rotted compost, lawn clippings mixed with compost, or lawn clippings as mulches. Keep in mind that the general recommendation is not to collect lawn clippings, but if you do have them available they can be recycled as a mulch. However, you should never use clippings if they have been treated with an herbicide without waiting the amount of time specified on the product label.

Never apply more than a one-inch layer of fresh grass clippings at one time because they mat down and start to decompose anaerobically, making a gooey mess. Instead, wait until the clippings last applied have dried, and then apply another one-inch or less layer. The clippings can be tilled into the soil at the end of the season, adding organic matter to the soil.

To increase the effectiveness of a grass or compost mulches, place one to two moistened sheets of newspaper on top of the soil, overlapping the sheets as you place them in the garden, and then cover the paper with a layer of mulch. (Without a cover of mulch, the newspaper will easily be blown away by wind.) Do not use glossy color sections of newspaper, as they may contain heavy metals or other chemicals that will contaminate the soil. The newspaper will decay over the growing season and then can be tilled into the soil along with the layer of mulch on top.

Rock mulches are suitable for areas vulnerable to wildfires or non-plant areas, but they should generally be avoided around landscape plants because they are heat sinks. The rocks absorb heat during the day and then radiate that heat back at nighttime, increasing the heat stress and water needs of plants. Light-colored and white rock also reflects light back onto plants compounding

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