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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 https://pubs.wsu.edu

WHY NOT LANDSCAPE FABRIC?

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published – SEPTEMBER 19, 2014

WHY NOT LANDSCAPE FABRIC?

When we moved to our new house seven years ago, I had the enjoyable task of starting our landscape from scratch. My plan included a variety of trees in the lawn and plenty of shrubs and ornamental grasses in landscape beds around the house and the perimeter of yard. Adamantly opposed to using landscape fabric or geotextiles, the beds were mulched with a four inch layer of medium size shredded bark after planting.

Admittedly, landscape fabric or geotextiles are better than the black plastic used for mulching landscape beds in the 70s and 80s. They allow for the movement of air and water, where black plastic does not. Even though they do break down with time, geotextiles covered with mulch last longer than the black plastic in the same situations.

So why am so I fervently against using landscape fabric? To make landscape fabric more aesthetically pleasing, it is often covered with a thin layer of mulch. Bark or wood chip mulches decompose with time, creating material in which weeds can grow. While rock mulches do not break down, blown in dust can create a layer of soil where weeds can grow. Plus, landscape fabric does break down with time, especially when not covered with a thick (3-4 in) layer of mulch that blocks UV radiation.

Many gardeners who have used landscape fabrics will tell you it is not a permanent solution to weed control. Weeds will invade the beds, and then the fabrics become a nightmare, especially when Bermuda grass and field bindweed (wild morning glory) are involved. The roots or rhizomes of these trailing pernicious weeds find their way into the fabric fibers, making it impossible to rogue them with pulling. If you do try to pull them out, the fabric comes with them. Arrrgh!

The best way to control weeds in landscape beds is with organic mulches. I prefer the look of shredded bark, but wood chips are just as effective and less expensive. WSU Extension Horticulturist, Dr. Linda Chalker Scott, prefers wood chips because of some of the problems that bark shredded bark can pose. She favors wood chips because of the possible contamination of bark with salt or weed seeds and because of the sharp, pointed fibers of softwood bark are not “gardener friendly.” Plus bark can resist water penetration because of the waxes they contain.

Whether you use bark or wood chips as a mulch, the layer should be 4-6 in thick. This blocks light from getting to the soil and helps maintain soil moisture. I do advise keeping mulch away from directly around the base of trees and shrubs. It retains moisture and excludes air. A thick layer of mulch touching a plant’s base can lead to collar rot causing serious damage to trees and shrubs.

Chalker-Scott points out that if you are trying to reclaim a site or an area with serious perennial weed problems consider using a 8-12 in thick layer of wood chips. She cautions you to taper down to a very shallow layer close to trees and shrubs.

Mulching with bark or wood chips is not a place-it and forget-it situation. They decompose with time, adding organic matter to the soil. Periodically you will need to add fresh mulch on top of the old, to maintain the weed controlling 4-6 in layer, being careful to keep the mulch away from the base of plants. By the way, fall is a great time to renew the bark or wood chips in your landscape.

Published: 9/19/2014 12:27 PM

Using Landscape Fabric

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

GARDEN TIPS – SEPTEMBER 19, 2014 – WHY NOT LANDSCAPE FABRIC?

When we moved to our new house seven years ago, I had the enjoyable task of starting our landscape from scratch. My plan included a variety of trees in the lawn and plenty of shrubs and ornamental grasses in landscape beds around the house and the perimeter of yard. Adamantly opposed to using landscape fabrics or ‘geotextiles,’ I mulched the beds with only a four inch layer of medium-size shredded bark after planting.

Admittedly, landscape fabrics or geotextiles are better than the black plastic used for mulching landscape beds in the 70s and 80s. The fabrics allow for the movement of air and water, where black plastic did not. Even though they do break down with time, fabrics covered with mulch last longer than black plastic in the same situations.

So why am I fervently against using landscape fabrics? To make landscape fabrics more aesthetically pleasing, they are often covered with a thin layer of mulch. Bark or wood chip mulches decompose with time, creating material in which weeds can grow. While rock mulches do not break down, blown in dust can create a layer of soil where weeds will also grow. Plus landscape fabrics do eventually degrade, especially when covered with only a thin layer of rock or bark mulch that does not block UV radiation well.

Many gardeners who have used landscape fabrics will tell you they are not a good solution to long-term weed control. Weeds will invade the beds and then the fabric becomes a nightmare, especially when Bermuda grass or field bindweed (wild morning glory) are involved. The roots or rhizomes of these trailing pernicious weeds find their way into the fabric fibers, making it impossible to rogue them out with pulling. If you do try to pull them out, the fabric comes with them. Arrrgh!

The best way to control weeds in landscape beds is with organic mulches. I prefer the look of shredded bark, but wood chips are just as effective and less expensive. Dr. Linda Chalker Scott, WSU Extension Horticulturist, prefers wood chips because of problems associated with shredded bark. She favors wood chips because of the possible contamination of bark with salts or weed seeds and because the sharp, pointed fibers of softwood bark cause tiny slivers in gardeners’ hands. In addition, bark mulch may resist water penetration because of the waxes and lignins contained in bark.

Whether you use bark or wood chips as a mulch, the layer should be 4-6 in thick. This blocks light from getting to the soil, preventing weed growth. The layer also helps retain soil moisture. I advise keeping mulch away from direct contact with the base of trees and shrubs. A thick layer of mulch touching a plant bases can lead to collar rot causing serious damage to trees and shrubs.

Chalker-Scott recommends applying a 8-12 in thick layer of wood chip mulch if you are trying to reclaim a landscape site with a serious perennial weed problem. She cautions you to taper down to a very shallow layer close to trees and shrubs.

Mulching with bark or wood chips is not a ‘place-it and forget-it’ situation. They both gradually decompose, adding organic matter to the soil. This is good. Periodically you will need to add fresh mulch on top of the old to maintain the weed controlling 4-6 in layer, being careful to keep the mulch away from the base of plants. By the way, fall is a great time to renew the bark or wood chips in your landscape.

Published: 10/9/2014 2:40 PM

THINGS GARDENERS SHOULD KNOW

written by Marianne C. Ophardt WSU Extension Faculty for the Tri-City Herald, Kennewick, WA LANDSCAPE FABRIC: Twenty years ago, many area landscapes were mulched with black plastic and rock mulches. This combination made it particularly tough to grow trees and shrubs successfully. The black plastic didn’t allow for the free movement of water and air into the soil. Plus, the plastic combined with the rock mulches increased soil temperatures and greatly stressed plants. The black plastic didn’t last indefinitely and weeds became a problem again before long. Eventually ‘geotextiles’ came along and started to replace the troublesome and restrictive black plastic. These woven or spun materials allowed for the free movement of air and water. They also were effective in reducing germinating weeds. Today, geotextile landscape fabrics have become the standard in landscaping, but they have not been the ultimate answer to weed management. Landscape fabrics do have some drawbacks. First, they do degrade over time, especially when exposed to sunlight. Ones that are UV resistant will last longer. Usually a top layer of mulch is applied over the fabric, increasing its life and the appearance of a landscape bed. If an organic mulch (my preference) is used on top of the fabric, eventually the mulch starts to decompose and will become colonized by weeds. Weeds are kept out longer if inorganic rock mulches are used… but eventually weeds will show up whether organic or rock mulches are used over the fabric. Removal of weeds in these situations is made difficult because the weeds’ roots grow into the fabric. Also, the roots of landscape plants tend to grow near the soil surface and grow into the fabrics. When the fabric breaks down and removal is desired, plant roots are damaged. While the use of geotextile fabrics can deter weeds for a some time, it’s better not to use them. They don’t provide permanent weed control in permanent landscape situations. Organic mulches, such as shredded bark, coarse compost, or wood chips, are the best choice for managing weeds in home landscape beds. They are attractive, their decomposition nurtures beneficial soil organisms, and their breakdown helps improve the soil. PRUNING PAINT: ‘Wound dressings’ or ‘wound paints.’ have been around for years and have been used by conscientious, caring gardeners trying to keep their plants healthy. It was thought that these wound dressings would stop wood rot and prevent the entrance of decay organisms and boring insects when painted on tree wounds. Unfortunately, the various wound dressing preparations do just the opposite. Wound dressings seal in moisture, actually creating a better environment for the decay organisms. Some of the materials used delay callus formation and the closing of the pruning wounds, increasing the amount of decay that can occur. They can also increase the amount tissue damage at the wound site, increasing the overall injury. Plus, these materials do eventually dry out and crack, making it easy for pathogens to find their way in. The use of wound dressing has not been recommended by tree care professionals and horticulturists for many years. Products containing collagen, pectin, hydrogel, and aloe gel have all been touted in recent years as natural compounds that will enhance tree healing. Unfortunately, there is no evidence that these new materials or the old materials hasten healing or prevent decay. The best way to promote healing of pruning wounds is to make proper pruning cuts and then leave the wound open to light an air. For other physical wounds to trunks, it’s important to make a smooth edge to the wound and leave it open to air and light. There is no good reason to apply a wound dressing or wound paint to pruning cut, trunk injuries, or cracks in the trunk. PHOSPHORUS FERTILIZERS AND FLOWERING: No doubt you have seen specialized fertilizers on the garden store shelf. Some of these are ‘formulated’ to promote flowering of annuals and flowering shrubs, such as roses. Most of the flower enhancing fertilizers contain higher levels of phosphorus. You can probably find a good number of references and web sites that recommend the application of phosphorus fertilizers to promote flowering, but the truth is that extra applications of phosphorus will do no good if there is an adequate level of phosphorus already present in the soil. Most of our local garden soils have adequate levels of phosphorus, especially if someone has applied fertilizers containing phosphorus in the past. Phosphorus does not readily leach out of the soil, as does nitrogen. By applying excess phosphorus you will decrease soil health. By decreasing soil health, you decrease plant health. Weaker plants are more subject to attack from diseases and insects and susceptible to nutrient deficiencies… setting up a greater dependency on chemicals. So don’t add extra phosphorus from flower promoting fertilizers unless you know your soil is deficient in this nutrient. Is your soil deficient in phosphorus? Get a soil test done to find out. LAWN MOWING: Mowing… it’s the most tedious lawn task, but it’s also one of the most important. Mowing at the right height, the right frequency, and the right way go a long way to providing you with a nice looking, healthy lawn that’s able to resist invasion by weeds and attack by pests. Kentucky bluegrass lawns mowed too high will develop thatch more quickly and will lose a nicely manicured look. Mowing too low is even worse than mowing too high. Low mowing decreases the leaf surface area, decreasing the photosynthesis needed for plant growth. This leads to weaker grass plants with shallower, weaker root systems. This makes the grass plants more prone to stress from possible drought and heat stress during the summer. The recommended mowing height for Kentucky bluegrass lawns in our region is 2 to 2.5 inches. Lawns should be mowed often enough so that no more than 1/3 of the leaf blade is removed at any one mowing. ‘Scalping’ the lawn by removing more than 1/3 of the leaf blade will injure and weaken grass plants. If you go away on vacation and the lawn gets away from you, mow first at the highest height you can achieve on the mower. Once those clippings are dry, mow again at the recommended height in a different direction. (However, it would be better to have someone mow in your absence.) For the best looking lawn, mow your lawn in a different direction every one or two mowings. Mow at right angles to the previous mowing. If you always mow in the same direction, the grass will have a tendency to be pushed in that direction and it won’t stand up well. Be sure to keep your mower blade very sharp. Dull blades tear the ends of the grass, which weakens the grass plants by damaging more leaf tissue and leaves a lawn with an off-color, less manicured appearance.

Published: 6/4/2005 1:40 PM

PLANTS SUFFER LEAF SCORCH FROM HOT WEATHER

written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Days and weeks of intense summer heat and sun in our area cause trees, shrubs and other plants to loose large amounts of water through the pores, called “stomata,” in their leaves. This loss of water from the leaves is a process called transpiration.

The purpose of transpiration is to keep plant leaves from cooking in the sun. It’s a plant’s natural method of keeping cool. At least 95 per cent of all water absorbed by a plant’s roots is used for transpiration and cooling plant leaves. Water is also used by plants for normal cell function and growth. In addition, roots absorb water containing nutrients needed for plant growth.

When not enough water reaches the leaves, the leaf tissues become “burned” or scorched. Leaf scorch is a common problem that arises during our area’s hot, dry summer months. It appears as brown to tan, dry leaf edges. This necrotic tissue may also extend into the areas between the leaf veins. On needled evergreens, needles will turn reddish purple first and then brown, especially on spruce.

Leaf scorch will typically be more severe on the south to southwest side of a plant or on the side more exposed to sun, heat and wind. When a tree or shrub exhibits leaf scorch, it’s an indication that not enough water is getting to the leaves. The most logical cause of leaf scorch is a lack of adequate soil moisture. If leaf scorch starts showing up on a tree or plant in your yard, check the soil moisture first.

For large shade trees and shrubs situated in lawns, the 15 to 20 minutes of irrigation applied every day or every other day to keep turf green is simply not enough. These larger plants need a deep watering once a week during hot summer weather. How deep is deep? A “deep” watering for a tree only needs to moisten the soil to a depth of 12 to 18 inches. That’s where most of the water absorbing roots of trees are located. For other garden plants check the soil and make sure it’s moderately moist. The exception is a xeric or low-water-use landscape with drought tolerant plants. These plants can withstand drier soil once established.

A lack of adequate soil moisture isn’t always the cause of leaf scorch. There can be underlying causes preventing water from entering the plant or keeping water from reaching the leaves. These causes include:

1. Inadequate root systems that are unable to absorb enough water to provide for the plant’s needs. This may be due to a lack of room for root growth, damage to roots from construction activities or cultivation, or compacted soil that impedes root growth.

2. Injuries to tree trunk or plant stems can prevent the upward movement of water to the top of the plant, even if the roots are healthy and able to absorb adequate amounts of water.

3. Girdling or restricted roots “choke” a plant and interfere with both the absorption and movement of water to the top of a plant.

It’s important to point out that certain plants aren’t well adapted to our hot summer conditions and are prone to drought stress and leaf scorch. Plants like flowering dogwood, Japanese maple, blueberry, and rhododendron do best if planted where they’re protected from hot afternoon sun. It also helps to keep their roots cool by mulching with shredded bark or compost .

While moderate leaf scorch itself is not a fatal blow to a tree or most woody and perennial plants, the deficit of water and the damaging stress it represents is serious and can lead to a plant’s decline and eventual demise. If a tree or plant in your yard or garden starts showing signs of leaf scorch, you should try to determine the cause and take immediate steps to rectify the situation. Don’t let your plants continue to suffer in the heat.

Published: 8/11/2007 2:38 PM

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