Washington State University Extension

Garden Tips

Archive for September 2016


GARDEN TIPS – Written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Published August 28, 2016

I have to admit that when I relocated to Washington a long time ago, I was deathly afraid of spiders. Since then I have come to appreciate these much misunderstood beneficial arachnids.

Spiders are not insects. They have two body segments, eight legs, and eight eyes. They also have a pair of chelicerae, appendages resembling fangs but serving as jaws. In addition they have a pair of pedipalps, appendages resembling small legs that are used for sensing objects, for helping construct a web, and for holding onto prey. Unlike most insects, spiders do not have antennae or wings, but they are capable of producing silk their entire life.

What makes spiders beneficial is that they prey on insects, providing us with natural pest control. What makes them scary is their appearance and the fact that almost every type of spider is venomous. However, that does not mean they are harmful to us. Generally, most spiders do not possess venom that causes humans any injury. If their venom does cause a problem, it usually just an itchy bite. Out of the approximately 50,000 species of spiders that exist in the world, only about 25 of them are capable of causing human illness and none are considered deadly.

The reason spiders possess venom is to aid them in gaining control over their prey who no doubt try to escape when captured. Spiders are not intent on attacking us and “taking us down” as prey. The most venomous spider in the US is the black widow and it only bites humans when disturbed or threatened.

Spiders take different approaches in capturing their prey which are usually insects. Some build sticky webs and wait for an unsuspecting insect, such as a fly, to become stuck in the strands. As the insect struggles, the spider injects it with venom to immobilize or kill it. Other spiders build webs with dry silk and quickly attack their prey when the vibrating strands alert them of their dinner’s presence. About half of all spider species do not spin webs for capturing prey. Some spiders hunt down their victims, while others sit in hiding to wait for dinner to pass in front of them.

As fall approaches, many homeowners fearful of spiders migrating indoors from outside, will spray their yard and home foundation with pesticide to kill the spiders. This is shameful. Spiders are our friends, eating all sorts of other insects and providing natural pest control just like preying mantids, lady beetles, and other beneficial insects.

This spraying is also misguided because most of the spiders found living inside a home are house spiders, not outdoor spiders. House spiders are ones adapted to indoor conditions that are not favorable to outdoor spiders. House spiders arrive in homes as egg sacs with building materials used to construct the home or on household goods. They spend their lives hidden somewhere within or under the home. When you see them in the early fall roaming about the house, they are in search of females for the purposes of mating.

Outdoor spiders are not well adapted to the limited food and water supply available inside a house. They will stay outdoors, not migrate inside to find a cozy place for winter. They are adapted to surviving winter outdoors. If they get lost and come indoors, they will die.
If you do have a number of house spiders start appearing in your house in the fall, they have come from somewhere within the house. While creepy, it should not cause you sleepless nights. Just buy a bunch of sticky spider traps at the hardware or grocery store and place them along baseboards in the corner of rooms or under the beds. If cobwebs are a problem on the outside of your house or on shrubs, simply brush them off with a broom or use a forceful spray of water to wash them off. Remember, spiders are our friends.

Spiders are much misunderstood creatures. To learn more about spiders go to the University of Washington Burke Museum website that debunks many myths you may have heard about spiders at:


GARDEN TIPS – Written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Published August 21, 2016

If you ever hear gardeners talking about green manure you might be wondering just what type of animal produces green manure? It is not produced by an animal. They are talking about cover crops. These are crops planted in the garden and tilled back into the soil primarily for the purpose of adding organic matter, but they also provide additional benefits. These other benefits include the reduction of soil erosion from wind and water, the relief of soil compaction by crop roots, the discouragement of weeds by shading, and decreased nutrient loss over the winter by temporarily tying up of nutrients.

I do not know many area vegetable gardeners who plant cover crops, but they should consider it. Late summer through early fall, mid-August to mid-September is a good time for area gardeners to seed a cover crop in the garden. This is early enough to give them time to grow before cold weather begins and while irrigation water is still available.

There are different types of cover crops that can be used in gardens or on farms, including grains, grasses, legumes, and broadleaf crops, each with different benefits and management techniques. For home gardeners, an important consideration in the selection of a cover crop is how easily it can be worked into the soil next spring. Unlike farmers that utilize cover crops, most home gardeners do not have tillage equipment that makes it easy to incorporate the plant material into the soil.

Home gardeners will want to pick a crop that grows quickly and can be easily worked into the soil. Some cover crops may get too tall to easily work them into the soil without cutting them first. Depending on the crop, gardeners can use a rotary mower (without the mulching attachment), a string trimmer, scythe, or grass whip for cutting the crop down.

If you want to give cover crops a try, you do not need to end your vegetable gardening season early and remove plants that are still producing. Cover crops can be planted between rows or plants. If you have areas of the garden that are finished producing, remove the plants and seed the entire area.

Leguminous cover crops (vetch, clover, beans, peas) are desirable because they add both nitrogen and organic matter to the soil. However, legumes work in association with a special soil bacteria, called Rhizobia, that take or Afix@ nitrogen that is in the air. If you select a leguminous cover crop, you will need to inoculate the seed with the right Rhizobium species for that crop or purchase seed that is pre-inoculated.

When making the decision of what cover crop to grow, consider the advantages and disadvantages of each. For more information on selection consult the WSU Extension factsheet Cover Crops for Home Gardens East of the Cascades FS117E found at In addition, a good resource on the use and management of cover crops in the garden is Methods for Successful Cover Crop Management in Your Home Garden FS119E at

Once you decide what cover crop to plant, ask your local garden or feed stores if they carry the seed. If not, there are on-line sources of cover crop seed including Territorial Seed Company (, High Mowing Organic Seeds (, and Peaceful Valley Farm & Garden Supply (


GARDEN TIPS – Written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Published August 14, 2016

Tree anomalies have a way of occurring from time to time over the years. They are signs of potential problems that justifiably alarm tree owners. Recently, some local tree owners became concerned when a considerable number leaves on their trees started to turn yellow and drop on the ground.

Midsummer leaf drop occurs before the arrival of fall and is usually related to heat stress. As you can imagine, excessively hot days can stress trees, especially species not well suited to hot climates. The root systems of these trees are not able to keep up with the water demands put on the trees by high temperatures. Some types of trees respond to heat stress by getting rid of some leaves, thereby limiting the loss of water through their leaves. Other types of trees develop leaf scorch (brown, dry edges on the leaves) when they cannot keep up with the water demand caused by hot weather.

In our area, sudden yellowing and dropping of numerous leaves due to heat stress has been noticed on birch, cherry, Liriodendron (tulip), linden, sycamore, and willow trees. This year’s midsummer leaf drop was probably more pronounced because of the abrupt change from moderate weather to high temperatures.

Drought stress can also lead to tree leaf drop, especially when paired with heat stress. During hot summer weather, it is important to provide your trees with the water they need via deep watering. Large shade trees seldom receive adequate water when getting moisture only through lawn irrigation. It is important in hot weather to provide trees with a deep watering at least once a week.

How much water do trees need? They need a lot of water because they lose a lot through the pores, called stomata, in their leaves. Adequate irrigation is extremely important. To determine how much water your shade tree needs, go to the WSU Irrigation website and use their Tree Water Management Calculator at

A Supposedly “Fruitless” Plum Tree with Fruit: It can be annoying for owners of a flowering plum tree when their supposedly fruitless plum occasionally or frequently produces a prodigious crop of plums. When this happens, I get asked the same two questions. Why did this happen and are the fruit edible?

The production of fruit on ornamental plums is not a reliable occurrence, but it can happen if their bloom overlaps that of other types of plums. Typically, purple-leaved flowering plums bloom in early spring before other plums are flowering, limiting the possibility of cross-pollination and fruit development. Before buying a flowering plum tree, check with your nursery to make sure the cultivar you are selecting is rarely fruitful in our area.

As to edibility, the fruit can be eaten, but are generally of poor quality for eating. The trees were bred for their beautiful flowers, not their fruit. If you are a thrifty gardener, you might try making jam with the fruit and see if it is tasty enough to be worth your time and trouble. Do not use the fruit if the tree has been treated with pesticides not labeled for use on edible fruit trees.

Garden Note: Whenever applying pesticide to a tree with edible fruit, check the label for the “days to harvest” or the number of days after application that you must wait before harvesting the fruit. Also, make sure the type of fruit receiving the application is listed on the label.



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