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Birches and a number of other tree species, including ornamental and fruiting cherries, will drain lots of sap if they are pruned in late winter or spring. There's nothing that can be done to stop it once the flow has begun. Painting the cut with sticky "wound paint" isn't effective and isn't recommended by Washington State University plant specialists.
The flow usually stops. Trees with this characteristic are best pruned in fall or very early winter before the sap begins moving.
There are many organic strategies for controlling aphids. A forceful stream of water will dislodge aphids and may be all you need to keep down the population.
Beneficial insects such as ladybeetles, syrphid flies, lacewings, and wasps eat a great many aphids. Encourage these predators and parasites by growing flowers that provide nectar and pollen. They prefer shallow flowers like yarrow, parsley, cilantro, sweet alyssum, and daisy. These beneficials feed on nectar that is easily reached on the surfaces of flowers with these open, shallow shapes.
On many plants aphids are a problem only on the soft new growth. Observation will show you that aphids tend to cling to the new shoots on roses, for instance. Avoid overusing nitrogen fertilizer to limit the production of lush, aphid-prone shoots. Using too much fertilizer, too often, is a common mistake in gardening and it will contribute to pest and disease problems.
Black bean aphids like beans, but they like nasturtiums even more. To control aphids on your crop of beans, grow a patch of nasturtiums nearby as a trap crop. When the flowers are full of aphids, rip them up and destroy them.
When aphids get to unacceptable levels and you just can't wait for the beneficial insects to get the population under control, try insecticidal soap. We don't recommend home-made combinations of bath, laundry or dishwashing soap, because they may not be effective and may contain ingredients that are phytotoxic (hurt plants). Insecticidal soaps, on the other hands are blends of the most effective fatty acids and have been tested on plants for toxicity. They are very safe but, as with all pesticides, follow label directions carefully.
Topping, heading or stubbing back the major branches or trunk of a mature tree is nothing more nor less than an arboreal atrocity. The practice destroys the aesthetic value of the plant, and it will also very likely lead to disease encroachment and perhaps the ultimate death of the tree.
A deciduous tree's response to topping is to produce a mass of epicormic shoots or watersprouts which are very weakly attached. They stand up like a bunch of broom shoots. When these shoots grow larger after a few years, they are very prone to breaking off and can cause serious damage.
In addition, the large wounds created by topping a broadleaf tree are seldom able to heal or callous over completely. These wounds are open highways into the tree's internal structure for decay organisms, which will reduce even more the stability of the plant over a period of time. Blowdown or breakage may very likely be a future problem.
Conifers, all plants commonly thought of as "evergreens", when they are topped, take on an especially unnatural and unsightly appearance. One or more of the nearest lateral (or side) branches will probably begin to grow upwards creating a misshapen and deformed plant. These too may be subject to breakage after they've grown weak new upright limbs.
Large trees, blocking views, may be limbed up or also thinned out by a competent arborist to open vistas under or through the plants. Large, mature trees, that for whatever reason cannot be managed this way, are also best removed and replaced with genetically smaller trees which will not grow so large as to obscure desirable views. Smaller trees, if they are healthy and well anchored, may be thinned to reduce the canopy and to allow the wind to blow through trees rather than into them. Look for arborists registered as certified with the ISA (International Society of Arboriculture) if any major tree work needs to be done. This registration makes the person a "certified arborist" with special professional training. Mature trees are far too valuable to be topped indiscriminately.
Nigbtcrawlers, which are sort of overgrown earthworms, are very beneficial to your garden soil. Unfortunately, they also shove little piles of soil, called castings, up to the soil surface. Some gardeners, especially those who want lawns like putting greens, find this most annoying.
Nightcrawlers draw their nutrition from the organic matter in the soil that passes through their bodies. The castings (what comes out the other end) are extremely fertile. In compact or poorly drained soils, the castings often appear at the surface of the soil. Ironically, the tunneling of the worms will benefit these compacted soils the most, since their action opens up soil and enhances drainage.
So what can you do? It's not advisable to use pesticides to kill a beneficial organism that is occasionally a nuisance. If you are seeing the castings in border areas, put an organic mulch around your bare soil under trees and shrubs. The castings will still be there, but you won't see them. And the mulch will be beneficial. Lightly rake lawn areas when the castings become objectionable in turf.
Wood ashes contain potassium, a necessary plant nutrient. They are also very alkaline, so they help bring our naturally acid soils closer to a neutral pH. Wood ashes used in moderation can be good for the vegetable garden or annual flower garden, especially where they can be thoroughly mixed into the soil before planting. Use about one heaping spadeful per square yard every two years. Do not use ashes from painted or treated wood, glossy magazines, or other non-wood debris.
Around existing plants, such as roses, you can work about one cupful into the top couple of inches of soil every other year. Be sure not to use ashes around plants that do best in acid soils such as rhododendrons, azaleas, kalmias, heaths and heathers, magnolias, lilies, potatoes and blueberries.
If you enjoy fires regularly and have an average size lot, you will make far too many ashes each year for your garden to take them all. A limited amount of ashes can also be added to compost heaps to decompose with other plant materials. Sometimes in soil fertility test reports where the potassium is at excessive, toxic levels, the gardener has been over applying wood ash.
Rhododendrons and azaleas which are so much a part of western Washington landscapes, are unfortunately too often taken for granted. Far too many of these popular plants are subjected to all sorts of environmental and cultural stresses which cause them to become eyesores instead of the bright and attractive additions to gardens that they should be.
The culture of rhododendrons and azaleas which, by the way, are both members of the genus Rhododendron, should start out when they are purchased. Choose only healthy looking, well branched plants. Rarely is it a bargain to buy plants that are yellowish or whose foliage is sparse or undersized, or plants that just don't look healthy. It takes too much effort to bring plants that have been mistreated or neglected back to health. In some extreme cases, it may not be possible at all.
Although rhododendrons can be planted and transplanted at any time of the year, extra special attention and care must be provided if they are installed in the landscape during the drier spring or summer. Fall and winter rains provide those wonderfully moist conditions for them to re-establish; when these conditions are lacking, extra water must be provided by the gardener. Even established rhododendrons do not tolerate heat and drought stress well; it stands to reason that newly planted ones will tolerate it less.
When watering new rhododendrons, especially those that have been container grown, it is extremely necessary to make sure both the original container medium and the surrounding native soil are both completely moistened. Often the soil around the root ball is well watered but the container medium dries out, thus subjecting the plant to severe drought stress. Until the plant can get its roots out into the surrounding soil, it remains totally dependent on its original container soil to supply it with required water and nutrients.
Even balled-and- burlap, field grown plants can be subjected to the same sort of problems, particularly if the soil in which they were originally grown is very different in texture from the one they are being planted in. Water does not move very readily between soils of different textures.
Exposure is another matter to consider. Many rhododendrons do not do well if planted in full sun, especially with extra heat reflected from a wall. The south and west sides of buildings should be reserved for plants more amenable to such conditions.
Larger-leafed rhododendrons do best in filtered sunlight under high trees or they can be planted on the east or north sides of structures. Take a tip from the fact that these larger leafed types have generally evolved in rather woodsy environments. If you want to use some of this genus in sunny or open settings, use azaleas or the very small leafed rhodies.
Rhododendrons will only grow well in well drained soils. They usually languish and die in tight, clay soils. Even clay soils that have been amended with organic matter may not be suitable if planting holes are dug in the tight material. Excess water must be able to quickly exit the root area of all rhododendrons, or else they become subject to root rots.
If you have a heavy soil, it is far more prudent to plant them on top of the ground and mound a nice, loose, humusy topsoil around them. Berms, mounds or raised beds are often the only answer where the native soil is largely composed of sticky, wet clay.
Don't plant azaleas or rhododendrons any deeper than they grew in field soil or in containers. Sometimes placing one as little as one inch deeper than it previously grew will cause the plant to go under stress and eventually die. Organic mulches of bark, sawdust, shavings or compost should always be added soon after planting. Rhododendron roots are most vigorous and healthy if they are always moist and cool. A three inch layer of a permeable, organic material is not too much; keep it a couple of inches away from the crown.
As with blueberries, a close relative, soils for rhodies should be somewhere within a pH range of 4.5 - 6. Soils which have previously been heavily limed may not be appropriate, although soils which are very, very acid may benefit from an application of dolomite lime. Before ever applying lime to a planting, it would be wise to know what the actual pH is by having a soil test done.
Rhododendrons will generally be more vigorous, healthy and will bloom better if some attention is paid to managing their soils' fertility. Like most woody plants, they will really respond to an annual application of nitrogen using something like ammonium sulfate or urea. Application should be made at the time growth starts in spring. Acid-loving plant fertilizers containing phosphorus and potash in addition to nitrogen can also be used.
Pruning is not normally necessary, but if they do grow beyond their allotted space, they can be dealt with right after they finish flowering. Always make your cuts just above a whorl of leaves, or where one used to be. Look for the old leaf scars; there should be latent buds there. Of course, it would be better if rhododendrons did not have to be pruned. Choose varieties that will not outgrow their place in your landscape.
