Q: I have several varieties of hot/spicy peppers that we are growing to make hot sauce. Is it too early to plant the starts? I was thinking of waiting until later in June, but looks like temperatures may be increasing sooner.
A: Waiting until late June would most likely give you the best results for growing your peppers. Temperatures are on a bit of a roller coaster, with nighttime temperatures still dipping into the low 50s. The Oregon State University Extension publication “Spice Up Your Garden with the Perfect Pepper” (bit.ly/3PX7iTg) say s to plant when the air temperature reaches 70 to 80 degrees during the day and 60 to 70 degrees at night.
Cloches are a great idea to help keep your plants warmer. The Cornell University article “Growing Guide — Peppers” (bit.ly/3MbDW0A) also suggests using black plastic or row covers. As mentioned in the article, be sure to remove the row covers and/or cloches during the day to prevent the sun from overheating and damaging your plants.
— Jan Gano, OSU Extension master gardener
Is vinegar weed killer bad for the environment?
Q: Is some vinegar bad for environment? And is there also “good” vinegar that isn’t harmful that can be used as a weed and grass killer?
A: Acetic acid (AKA vinegar) products have low toxicity and break down quickly in the environment. A study by the University of Maryland found that 20% vinegar (which is four times more acidic than what you have in your pantry) is effective as an herbicide on some plants. It doesn’t work on established plants, particularly those with taproots, and works only temporarily on grasses. You can read the full study at bit.ly/3GMl9HP.
— Kris LaMar, OSU Extension master gardener
What can I do to help my withering peonies?
Q: I noticed yesterday that my peonies were turning black and withered. I was so happy to see them come up looking beautiful and healthy after all the strange weather. I have not fertilized them, as the dogs are attracted to fertilizer and it is not healthy for them to eat. What should I do?
A: This sounds like botrytis blight, a fungal disease. Remove all of the blackened leaves and flowers and clean up the area around the plant. Bag and throw the diseased plant material away.
Pure neem-oil could be used on the plants, but most of the problem can be taken care of with good sanitation and removing any diseased leaves.
Organic fertilizers such as compost (which breaks down very slowly and usually does not attract dogs) will help the plant. Liquid fish emulsion may attract your dogs, but they won’t be able to eat much.
Clean up and cut the peonies down to the ground in the fall.
— Sheryl Casteen, OSU Extension master gardener
Why are my tomato starts spindly?
Q: What could be the cause of my heirloom tomatoes, started from seed, becoming spindly after being transplanted into my raised beds. The seed was planted March 3 and transplanted May 10. They were hardened off starting one week before with nighttime protection in my garage.
A: Tomatoes are one of the most popular vegetables grown in home gardens. They love the heat and require full sun and a long, frost-free season. Tomatoes that do not get a minimum of six hours of sun per day will become weak and spindly.
Typically, tomatoes can be planted outdoors from late May through early June. This year, with the unusually cool spring weather, May 10 may have been too early to plant outside. The soil temperature in your raised beds needed to be at least 60 degrees to prevent growing problems with the plants’ fruits and roots.
Can this dogwood be saved?
Q: We had a small miniature dogwood professionally planted last year. That year, it flowered but didn’t get many leaves and didn’t grow much. We understand it is a slow-glowing tree. This year, it had nice blooms but, again, very few leaves. It now looks pretty sick to me and I’m wondering what is wrong with it. Do you think there’s anything we can treat it with or any ideas what might be going on with it? Or do we just need to replace it?
A: The tree is probably on its way to dying. It is most likely a fungal disease. With dogwoods, once a fungal disease in the system, it will cut the flow of nutrients throughout the tree, causing exactly what you have mentioned — fewer and fewer leaves and then dieback of the leaves.
Unfortunately, you cannot cure it; only try to keep the disease down. Unless you want to spray it many times each year, I would replace the tree and not plant another dogwood in the same spot. Spores can live in the soil for a long time and may infect another dogwood. You might want to leave that spot unplanted for some time and maybe put a non-living decoration there.
— Sheryl Casteen
What’s causing Japanese maple’s defoliation?
Q: The mature Japanese maple in my yard was just starting to leaf out when the April freeze hit. At that time, it dropped about half its leaves, and they do not appear to be re-budding.
Previously, it has appeared very healthy and had a nice thick canopy. I water it about once a month during the summer, and watered especially deeply and more frequently during last year’s heat dome. I do notice that the tree has a fair amount of lichen growing on it. It also has a lot of dead twigs on the branches that lost leaves. The main small branches are green under the bark though.
Is the tree in danger of dying? Should we fertilize it this spring or summer to help compensate for the missing photosynthetic ability? If so, what should we use and how much?
A: There are at least two possibilities to explain why your maple has defoliation. One is the late, unexpected freeze, just as foliage was emerging. The foliage won’t be replaced this year.
A second, more serious possibility would be a soil disease called verticillium wilt, a fungus that causes defoliation. It is not treatable and is always fatal to the tree. This can be diagnosed only in a lab by examining a branch and soil testing.
It’s your call whether to do testing now or wait to see if the tree loses more leaves, giving it another year and hoping for a warmer spring.
Regardless, adding fertilizer is a bad idea. Without leaves, the plant cannot use the nutrients in the fertilizer because it cannot photosynthesize. Then excess nitrogen finds its way into waterways. So just keep the tree hydrated, especially if we get another heat dome.
— Kris LaMar
Tips for potted tulip care
Q: I had great blooms on my potted tulips this year. What is the best way to treat them so I can get them to bloom again next year?
A: Some kinds of tulips come back better than others. Some are grown for a strong bloom one year, and are best treated as an annual.
If your tulips were labeled naturalizing or perennializing, they are more likely to come back. Darwin hybrids, Fosteriana/Emperor tulips and some Triumph tulips are known to perennialize well.
To save them, cut the bloom stem when the flower wilts and allow the foliage to die naturally. You can then lift and store the bulbs, or store them in the pot, watering sparingly. Heavy irrigation and winter rains increase the chance of rot.
— Jacki Dougan, OSU Extension master gardener
Ask an Expert is an online question-and-answer tool from Oregon State University’s Extension Service. To ask a question, visit extension.oregonstate.edu/ask-expert.