Give Young Tree Roots Some Space

One of the best favors you can do for a young tree is to provide a grass and weed-free area around the trunk. This circle not only reduces competition for water and fertilizer, so the tree grows faster, but it also protects it from damage by mowers and line trimmers. Line trimmers are the number one cause of stunting and death of young trees.

Grass and other plants with roots near the surface are fierce competitors for water and nutrients. Not only do the grass roots get first chance at water and fertilizer, but grasses actually produce a substance which suppresses growth of competing roots.

I planted two apple trees one spring at the very same time as a neighbor across the fence was planting apple trees. He remarked that the trees looked the same now, but mine would probably grow faster because I had a “green thumb”. Two years later, when my trees were indeed twice the size of his he said, “You really do have a green thumb. What is your secret?”

I pointed to the ground around his tree trunks. Grass was growing right up to the trunk, but it was neatly trimmed with a line trimmer. Then I pointed to the 4 foot diameter circle of mulched soil around my trees. I pointed to the nice healthy bark on my trees and compared it to the nicks and cuts on the bark of his trees. I explained to him that the food made by the tree leaves travels to the roots in tubes just under the bark surface. When you cut through the bark, you disrupt the flow of food to the roots. A smaller root system means that tree branches grow more slowly also. I see trees which have been constricted near the soil line so badly that they will never recover. If the bark is cut all the way around the trunk, the tree will die.

You can put metal, redwood or plastic edging around the circle to keep the grass from growing into the circle. I prefer not to use concrete edging because the size of the circle needs to expand as the tree grows. You can cover the soil in the circle around the tree with weed barrier fabric. It shuts out the light to the soil below, and no plants will grow without light. You will probably cover the fabric with bark or some other attractive mulch. Eventually, the bark will break down and some weed seeds will blow in and sprout on top of the fabric. They are usually quite easy to remove. Two or three inches of bark alone, without the weed barrier fabric, will eliminate 90 % of new weed growth, unless grass is allowed to grow into it.

Mulch also reduces evaporation of water from the soil, which reduces the amount of irrigation water needed.

Warm Weather Brings Pests

Insects multiply much faster in warm weather. Aphids and mites are two pests to watch for. Aphids (often called plant lice) are small soft bodied sucking insects usually concentrated on new growth. They are usually green, but can also be pink or black. Aphids exude a sweet juice which drips on the ground. Ants are often associated with aphids because they use the juice for food. Mites are tiny eight legged pests which suck juices almost entirely on the underside of leaves. They are especially bad on needle-leaf evergreens. Yellow and brown mottling on leaves or needles is the most common symptom. Hold a white piece of paper under affected growth and shake. You will see tiny specks which move.

Both aphids and mites can be washed off plants. A strong stream of water will wash most of them off. However, soap or detergent will do a more thorough job of removing them. You can make your own mixture using dish wash detergent. A “Syphonex” works very well for this purpose. It is an inexpensive connector placed between two hoses or between the faucet and hose. It has a rubber tube which is placed in a bucket of strong soapy water. The soapy water is siphoned into water running through the hose. With a nozzle on the end of the hose you can wash these two pests off onto the ground and they will not find their way back up onto the plants.

Neem oil is a natural pesticide that is effective in controlling aphids, mites, and many other pests. Neem oil also controls leaf diseases such as black spot and mildew. Because of its dual action, it is my favorite pesticide for roses.

Spinosad is my newest favorite natural pesticide. It is effective on a wide range of insects because of its systemic action. It gets to leaf miners and borers which other insecticides do not reach. I use Spinosad for leaf miners in leaf vegetables such as chard, spinach and lettuce. It is also very effective against cabbage worms which also invade broccoli and cauliflower heads. It is effective against cherry maggot and codling moth worms in apples and pears. Spray it on the silks of corn to prevent ear worms. It is effective against the lace bugs which cause azalea and rhodendron leaves to become mottled and then turn white.

Because it is natural and non-toxic it can be used up until a day or two before harvest. Spinosad is toxic to bees and should be applied in early morning or evening when they are not active. Look for Spinosad on line or in the organic section of full service nurseries and garden stores. Look for “spinosad” on the active ingredient list. There are several brands available from Bonide, Monterey, Green Light and Ferti-lome.

Slugs and snails are another pest which must be re-treated regularly or they eat holes in leaves of annual and perennial flowers and vegetables. They only feed at night or in high moisture conditions, so you seldom see any signs except holes and their slimy trails. Snail and slug bait lasts about 2 weeks and then must be re-applied. The most common slug baits contain mesurol. However, baits with iron phosphate are safer for use around children, pets and wildlife.

Lace Bug Damage to Azaleas and Rhodendrons

I have noticed a lot of lace bug damage recently on azaleas and rhododendrons. Azalea lace bug (Stephanitis pyrioides) is a relatively new insect pest in the Pacific Northwest. According to Washington State University Hortsence web site (, “azalea lace bug attacks both azaleas and rhododendrons and may cause significant damage on both. Both adults and nymphs feed on the underside of leaves. Symptoms of damage are stippling, bleaching, or a silvery or yellowish (chlorotic) appearance of the leaves. The underside of the leaf will appear dirty due to the presence of insects (eggs, nymphs, and adults) and brownish or tar-like fecal spots, particularly along the leaf veins.

Heavily damaged leaves may drop from the plant. Adults are about 1/10 inch long with lacy, net-like, transparent wings. The azalea lace bug has smoky, brown markings on the wings, which distinguish it from the pale whitish-tan rhododendron lace bug. The young nymph is colorless to black and spiny depending on age.”

Several insecticides will control lace bugs. The problem is getting the bottoms of all the leaves thoroughly covered. Because of this, systemic insecticides which are translocated through the plant’s circulation system are most effective. Imidacloprid is a systemic pesticide which can be applied to the soil and is taken up by the roots. It is available in several brands including Monterey Once A Year Insect Control and Bonide flower and vegetable insect Control granules. Acephate (Orthene) is another systemic available in both spray and granular form. Spinosad is a new systemic organic pesticide which is effective on a wide range of insects. Neem oil is another organic pesticide which will control lace bugs. Three spray applications at 2 to 3 week intervals are necessary to control the multiple generations of this pest. One application of granules or Once a Year Insect Control is sufficient.

Continue Fertilizing Flowers and Vegetables

Most of us fertilize our plants when we plant them. With short season vegetables that mature in 60 days or less, such as radish, spinach and leaf lettuce, that is probably adequate. Longer season vegetables and flowers need repeat fertilization. Containers need the most frequent fertilization because of lower soil volume and more rapid drainage and evaporation. One of the first signs that plants need additional fertilizer is when lower plant leaves turn yellow.

Osmocote and similar coated, slow release fertilizers are my favorite for containers. They are the longest lasting. General purpose fertilizers such as 16-16-16 work well for flowers and vegetables.

If you are irrigating your lawn, another application of lawn fertilizer will keep it green through the summer. I always recommend lawn fertilizers which contain part of the nitrogen in a coated or slow release form. Organic fertilizers are naturally long lasting.