In 2021, Oregon gardeners searched for answers to myriad questions for the experts at Oregon State University Extension Service, but a few topics dominated. We’re talking mulch of all kinds, raised garden beds and how and when to prune. But the question that drew the most readers caught us by surprise.
And remember. If you have a question about gardening in Oregon, you can turn to Ask an Expert, an online question-and-answer tool from Oregon State University’s Extension Service. Faculty and master gardeners generally reply within two business days, usually less. To ask a question, visit the OSU Extension website, type in your question and include the county where you live.
These were the 10 most-read Ask an Expert posts on OregonLive in 2021.
10. Early rose pruning could cause dieback, result in re-prune next spring. (Jan. 16)
Q: With this warm early January weather my roses are growing like crazy and have several blooms. How can I protect the roses, if the weather turns cold again in February? – Multnomah County
A: In western Oregon/Willamette Valley the best time to prune is mid-February to early March. Pruning mid-month or later is recommended. This timing is suggested because generally we will have weather that encourages the plant to start growing. Pruning earlier (before the last frost or forecast bad weather) will cause the rose grower problems. See the full answer from Jack Master, OSU Extension Master Gardener Diagnostician, here.
9. When it comes to coffee grounds in compost, how much is too much? (Nov. 6)
Q: I was wondering if one could have too many coffee grounds in a compost pile?
I have a three-bin system and take in so many leaves from my neighbor’s yard each autumn (about 30 yard bags). This year, to help make sure I have a better balance, I’m getting a 5-gallon bucket of coffee grounds from a local coffee shop each week and am adding it to each bin on a rotating basis so that every third week, each section will get the grounds in addition to my kitchen waste.
I was wondering if my overall compost pH will be relatively balanced if I’m mixing the grounds with this huge abundance of leaves or should I dial back on the grounds? – Multnomah County
A: Interestingly, when a compost pile is composed of primarily plant matter (leaves, food waste, coffee grounds), it begins at a low pH and rises to about neutral. Low pH because the decomposition of plant materials results in the release of organic acids – initially. See how Linda Brewer, OSU Extension soil specialist, explains how to get the correct balance here.
8. Is it too late to prune a hydrangea? (Nov. 27)
Q: Is it too late to prune my hydrangea? I can see new buds of some sort down on the stems so I could leave those for next year’s growth if that’s called for, or do I just suck it up and prune next season? – Clackamas County
A: It turns out now is a fine time to prune, although it might be hard to clip while holding an umbrella! I’m attaching an article about hydrangeas; skip down to the “Pruning” section and you’ll get some good tips. – Rhonda Frick-Wright, OSU Extension Master Gardener (You can find more advice about pruning, this time perennials, here)
7. Is my HOA’s application of bark dust every year a waste of money? (Nov. 14)
Q: I live in an HOA in Corvallis. Every year or two we pay a lot to have the bark dust blown into the beds around bushes. It’s blown in to save the expense of humans shoveling it in. Is there a study of the relative costs of having bark dust blown in every couple of years vs. having larger bark chunks shoveled in by humans? In addition, would it be more cost effective in some less-obvious places to have the vegetation removed and the area covered by “path rock” (ground rock designed to not move over time)? Presumably all that would be required after that would be an infrequent application of herbicide. – Benton County
A: I can’t answer your question about the relative cost of different mulch applications – you will need to get bids from landscape contractors. Our purpose in the Extension Master Gardener program is to educate people about sustainable gardening methods, so what I can do is discuss the pros and cons of the materials you suggest and how they relate to soil health. If there are any plants growing in these spaces, then good soil health is critical for their longevity and growth. See the full answer from Signe Danler, OSU Extension Master Gardener instructor, here.
6. Compost, mulch or bark: What’s best for a flower garden? (Oct. 26)
Q: Which is better, mulch vs. compost vs. bark for our existing, healthy landscape flower garden? When/why/how to use some or all of these? We applied high quality compost 1.5 years ago when we first started the flower garden. Nothing added since then. – Washington County
A: Thanks for your question about the various mulches (they are all technically mulches) that you can put on your flower bed. They all have pluses and minuses. See the full answer from Rhonda Frick-Wight, OSU Extension master gardener, here.
5. When wood chips are added to soil, they compete with plants for nutrients. (May 29)
Q: We added about 3-4 inches of yard debris compost into our garden. We got it from a landscaping company as a soil amendment. The leaves on our cucumbers, beans, tomatoes and squash are all starting to turn yellow. The cucumbers have it the worst. I don’t know if it’s from the compost or what. I haven’t done a soil test. Any advice? Could I till in some top soil? – Clackamas County
A: Yes, you have nailed the “compost” problem. As you can see by the size of the wood chunks, what they call compost has not really broken down yet. What it is doing right now is trying to break down by using up the nitrogen in competition with your plants. Obviously, the “compost” is winning. See how Rhonda Frick-Wright, OSU Extension master gardener, explains in detail here.
4. Should raised garden beds be covered for winter? (Oct. 16)
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 also wonder if we should get something to cover the raised beds for the winter? – Lane County
A: 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. Pat Patterson, retired OSU Extension horticulturist, also has suggestions about a pH soil test. See Patterson’s full answer here.
3. Can I reuse potting soil? (Oct. 28)
Q: Is it best to store used potting soil for reuse in a sealed plastic container in the winter? It was used in outdoor pots, flowers and veggies. – Clackamas County
A: Yes, you can put it in a plastic tub sealed and stored in a dry place. You could also use burlap bags or heavy cardboard boxes as well. Keep the soil in a dry place and make sure the soil is dried out. Moisture can grow mold. It could be stored in the pot it was used in too. But there’s more you should know. See the full answer from Sheryl Casteen, OSU Extension master gardener, here.
2. Follow these steps to replenish nutrients in raised garden beds. (March 13)
Q: We have two raised garden beds in our backyard and I was looking for advice on how to best prep the soil for this year’s garden. Both garden boxes are approximately 8 -by-2 feet long by 2-feet wide by 2.5- feet deep. One was built two summers ago and the other was built last summer. Both beds were filled with compost when they were built.
Last year we added a little bit of compost to the original garden box and mixed it in with the soil that was already there. Other than that, we have not added anything else to the soil. Is there something that we should add to these garden boxes to replace nutrients used up by plants over the last couple of years before planting in them this year?
In one garden box we grew potatoes, bell peppers, basil, carrots and garlic. The newer of the two had tomato plants, green onions and carrots, although the tomato plants took over so the other veggies didn’t survive. – Marion County
A: Vegetables will usually do well for a year or so in a new bed, but because they are annual plants, they quickly deplete the nutrients, which must be replenished regularly. See the rest of the answer from Lynn Marie Sullivan, OSU Extension master gardener, here.
1. This clover lawn was allowed to grow to 8 inches. Now what? (Published Oct. 3)
Q: In the summer of 2020, we removed our lawn and replaced it with mini-clover. It filled in very nicely and we kept it mowed to about 2 to 3 inches.
However, this spring it looked so lovely that we couldn’t bear to mow it, so we let it grow unimpeded all summer. It has grown to about 8 inches, and we love it that way.
We are wondering whether we should mow it in the fall after the leaf fall has ended, in order to let it regrow afresh in the spring. We want to make sure that it is still tall next year. What should we do to help it get through the winter? – Marion County
A: OSU has done research on ecolawns but these studies were conducted under regular mowing schedules that kept the lawns to a height of about 3 inches. So we don’t have data on how to best manage this specific situation of a grown-out ecolawn.
That said, OSU Extension horticulturist Brooke Edmunds, had a few ideas. See them here.
— The Oregonian/OregonLive shares questions and answers from OSU Extension Service’s Ask an Expert tool each week at oregonlive.com/hg.