We’re well into gardening season and you might 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 it in, and include the county where you live. Here are some questions asked by other gardeners. What’s yours?
Q: All of my dahlias have ragged edges on the petals. Usually earwigs are the culprit, but this year, I’ve noticed more spotted cucumber beetles doing the damage. Is there any way to get rid of them without harming the bees?
I first noticed slug damage on the leaves soon after the dahlias began emerging this spring/summer, so I used Sluggo Plus, and that seemed to help. I have also used diatomaceous earth on the ground and Vaseline on the flower stalks to prevent earwigs, and so far, I haven’t found them hiding between the petals as I often did last year.
However, as you will see in my photos, my blooms have ragged petals with holes through them. I can’t even manage to get one flower that isn’t damaged. The diatomaceous earth and Vaseline won’t help against the cucumber beetles since they can fly in. How can I prevent them from eating my dahlias without hurting the bee population? – Washington County
A: Judging from your notes, you may well have a very large population of cucumber beetles. At this stage of their life cycle, you’re limited to daily hand-picking the adults, then dropping them into a cup of soapy water. In order to protect bees this year, you’ll need to rely on mechanical methods to limit the adult beetles, as mentioned above. This excerpt from our official pest management handbook highlights the details from the beetles’ lifecycle:
“Cucumber beetles overwinter as fertilized females and are active beginning in early spring. Adults lay eggs at the base of plants. Eggs hatch in seven to 10 days, and larvae feed on roots for about three weeks before pupating in the soil. Adults emerge two weeks later and feed on pollen, foliage, flowers, and pods.”
Thus, “Planting can be delayed until after the beetles have dispersed and deposited most of their eggs. Individual beetles can be picked off.”
Whenever planting or digging your tubers, keep a watch for wireworms, the larval form (youngsters) of cucumber beetles. You might even see the eggs. Destroy both on sight. (Images of the eggs and wireworms are here.)
Unfortunately, all the possible homeowner chemicals listed for managing cucumber beetles, including the organic products neem and spinosad, are toxic to bees. – Jean Natter, OSU Extension Master Gardener diagnostician
Q: Should I remove brown leaves from hydrangeas? The tips on some branches of my western cedar got scorched during the heat wave. What should I do? Just leave them? I’m thinking of cutting off the sun-damaged rhododendron leaves as I don’t want to look at that for three years. I am hesitant to do too much as we might get another heat dome this summer. Suggestions? – Clackamas County
A: Unsightly landscapes are a challenge, but your instincts about being cautious are spot on. The more damaged leaves you remove, the greater the chance of even more loss of water in the plants’ systems. And if you remove any tissue below the flowers, it stimulates new growth, which is even more susceptible to sun scorch than the old. Conifer trees have new-growth issues but the dead branches and leaves (needles) won’t recover. Wait to prune until next spring. Water all of these plants regularly and mulch around them (out to the extent of the root systems) with large-sized bark chips. This article has other ideas. – Kris LaMar, OSU Extension Master Gardener
Q: I bought some shrubs (Korean spice viburnum and ‘Tiny Tuff Ah Ha’ hydrangea) before the heat wave. They are recovering fine from those 110-plus days. Now is it better to leave them in their original plastic containers, transplant to fabric aeration bags for now or transplant directly in ground? I’m in The Dalles, 1/2 mile from the river. – Wasco County
A: Don’t plant or transplant now. Too-warm soil temperatures can kill young seedlings or cause cankers where the stem meets the soil line. Transplanting is stressful to plants without the added issues caused by high temperatures. Postpone planting or transplanting until cooler temperatures arrive.
Here is a paper on heatwave in the garden. – Mary Desisto, OSU Extension Master Gardener
Primrose can be a good choice to plant under low-hanging lace leaf maple. Marcia Westcott PeckLC- Marcia Westcott Peck
Q: I have a lace leaf maple in my front yard. It has a very good structure with a wonderful spread of foliage spring, summer and fall. However, because it does fill out so well, I cannot plant anything under it that will show during its leafing out period. Therefore, in the winter when the leaves are gone, I would like to add some color under the canopy of the tree to add color to the yard during the winter. Is there such a plant? I do not want to deplete the leaf canopy that I now have for the growing season. – Washington County
A: The winter garden doesn’t have to be bare of flowers and this article gives some planting ideas.
I also have a drooping laceleaf maple. Finding groundcovers that grow under it in the shade and don’t disrupt the tree roots is a challenge. I have a very dark-leaved ajuga that survives. Hardy cyclamen and some primrose are options. Even some Saxifrages, for example strawberry-leaf begonia (Saxifraga stolonifera) may spread and thrive, depending on how dense the summer shade is. – Jacki Dougan, OSU Extension Master Gardener
JasmineOSU Extension Service
Q: We just bought a new house and it has a fantastic garden. That said, it’s been neglected and I’ve been working over the past month to get some of the problems under control. I’m afraid to “treat” some of the things that I can’t identify and am hoping you can help. I’ve uploaded a few photos of the trees/shrubs that I’m hoping you can help identify. – Yamhill County
A: It is so fun discovering a new yard. Keep in mind that you don’t have to whip it into shape all in one season. Give yourself the gift of time. It will help if you observe it in all four seasons. You will see the plants bloom (if they do), which will help identification. You will also see the sun and shade patterns and any water issues. Then you can decide if you really like any particular plant.
Remember, this is now your garden, so you might not like what somebody else has planted and that is OK.
Plants are most easily identified by their blooms. I cannot identify the plants in your first two photos. If they are in your way remove them, or if you can wait until they bloom next year, they’ll be easier to identify. Since you can see the plants and can examine them closely, you might try using this on-line landscape plant identifying tool from OSU. If that doesn’t work, wait until they bloom.
You are correct, the third photo is a star jasmine, which is evergreen. Enjoy its heavenly fragrance. – Anna Ashby, OSU Extension Master Gardener
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