Fall is upon us and gardening is starting to wind down, but it isn’t over yet and you may have some questions. For answers, turn to Ask an Expert, an online question-and-answer tool from Oregon State University’s Extension Service. OSU Extension faculty and Master Gardeners reply to queries within two business days, usually less. To ask a question, simply go to the OSU Extension website and type in a question and the county where you live. Here are some questions asked by other gardeners. What’s yours?
Q: Our garden area is three raised beds and the remainder of the garden we usually put pole beans, zucchini, yellow squash and a winter squash in the soil. We try to rotate crops from year to year. I would like to ask if we should be enriching the soil with something now. I heard on In the Garden segment on KEZI to add a soil-building conditioner and garden lime. Just wondered what you thought about that. I have composted material that I add to the raised beds in the summer after we pull some crops and before we plant another crop. I have some ready to add now but wonder if it’s better to wait until spring so the rain doesn’t deplete all the good it does. I also wonder if we should get something to cover the raised beds for the winter? – Lane County
A: Have you done a pH soil test on your garden ever? This is the perfect time to take one. The local Eugene extension office can now do those by appointment only. That way you will know the pH, which determines whether your soil needs lime. You can also buy an inexpensive kit to test for pH. The fertilizer home kits tend to be inaccurate frequently. Compost is your soil conditioner. It can definitely be applied in the late fall and will break out nutrients only after the soil temperature reaches 50 degrees, as the soil organisms go mostly dormant below that temperature. Having some sort of cover for the garden in the winter is a very good idea. It helps prevent rain compaction of the soil. A cover crop is ideal as it catches any soluble nutrients and protects the surface and reduces weeds. That should have been started in late September, but will probably catch now. One of our favorites is red clover or scarlet clover or fava beans. Wetted newspapers, burlap sacks, leaves (preferably chopped), even bark chips all work. These are pulled aside in the spring before planting to allow the soil to warm more quickly. Your garden sounds very good and probably has extra fertility. – Pat Patterson, retired OSU Extension horticulturist
Should these trees be separated?
Q: I bought a tamarack in a 5-gallon container. It’s a beautiful tree about 6 feet tall. There is also a sub-alpine fir growing in the same container, close, like 2 inches away, also a beautiful tree. Question: Should these be separated before planting? They look great together, very natural pairing. – Clackamas County
A: It looks like you have one tamarack and two pines growing together in the pot. While we usually separate trees and space them out more from each other (even with intentional “cluster planting” we usually space them out least 2 or 3 feet apart) you could let them grow this way – as sometimes happens in nature. Keep in mind they can all grow up to be pretty large trees. You might take a hike in a natural forest and look for trees growing this close together to see for yourself how this might turn out. The individual trees will form somewhat lopsided crowns due to the mutual shade in the center of the cluster. With the stems so close together, there will be some pressure of the trunks pushing on each other as the trees grow in diameter. And the root systems will be lopsided and tangled up a bit, which can make for a weaker anchor. With these factors in mind, I would not keep them together like this close to any homes or other buildings. But if you have the space in more of a wildland setting, where there is less concern for creating “hazard trees,” it is really up to you and your own aesthetic preferences. – Glenn Ahrens, OSU Extension forestry specialist
How to treat cottony scale
Q: What is this on my red twig dogwood branches? Also, how to treat to control? – Douglas County
A: This appears to be cottony scale. Notoriously hard to control, scales are sap-sucking insects that prey on most kinds of trees and plants. Some species can cause a great deal of damage to the foliage on which they feed, while others are harmless. Resembling small bumps on twigs and branches, scales don’t look like most insects; therefore, they can easily go undetected.
Different species of scale vary in appearance and there are more than 1,000 species in North America. Some look like tiny oyster shells, some resemble fish or reptile scales, and there are plenty of others. During early growth stages, scales are called crawlers because they are mobile. These six-legged insects are smaller than a pinhead. Adult scales become stationary, feeding on one spot of the host.
Scale infestations weaken the host tree, and if the infestation is severe enough the tree can die. Damage to an infected tree can include:
- Branches covered with small bumps. (The bumps are actually the insects.)
- Yellow or brownish leaves
- Premature leaf drop
- Twig or branch dieback
- Slower growth.
Horticultural oils work by smothering the insect during any stage, while insecticidal soap is a natural pesticide that can be used to kill only the larvae. These methods usually require repeated applications.
Looking for tree ideas
Q: We just had to pull down our Himalayan birch due to birch bark borer. Can you suggest a good tree to replace it? It was 5 years old and had just begun providing the only shade in our northwest-facing backyard. – Lane County
A: When considering what you want to replace your tree with, you might want to contemplate planting a native species tree. Natives are better adapted to the Pacific Northwest’s climate and soil, making them generally easier to care for and less susceptible to pests and diseases.
If you are thinking about replacing your birch tree with another deciduous tree, there are several to consider. Red alders and big leaf maples are beautiful fast-growing trees. The Oregon white oak is slower growing but is very long lived. On the smaller size, cascara grow to 30 feet tall, but has gorgeous blooming flowers. Madrones are another good choice but do shed and should be keep away from areas you would like to keep clean, such as a deck.
There are also good native evergreen choices. Ponderosa pine is a fast-growing and very long-lived tree, while another to consider is the tall and stately western red cedar.
For more information on these and other native trees see: Gardening with Oregon Native Plants West of the Cascades and Recommended Native Plants for Home Gardens in Western Oregon. – Jan Gano, OSU Extension Master Gardener