Gardening is in full swing and if you’ve got questions, 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: We bought a house and found it had an untrellised grapes – Thompson seedless and Concords – growing in the grass. Long story short, we trellised them and the first year they did great. Every year since, the Thompson starts off great and then the leaves start yellowing, getting brown streaks, and the fruit never gets very big. We have clay soil and don’t fertilize the grapes because the former owner told me that once grapes are established you don’t fertilize them? I’m completely new to grapes so I took her at her word. We also have a dribbler sprinkler head that runs at the base of the grape vine for five minutes at 7 a.m. and 3 p.m. This year we followed the trimming/pruning/thinning regimen we saw outlined in YouTube videos, thinking that airflow might be the problem. Our leaves are still having trouble. – Washington County
A: Dr. Bernadine Strik, our expert on growing grapes in the home garden, gave me the following advice for your Thompson seedling grape plant:
Growing Table Grapes publication
She also gives pruning courses online. One is for grapes. Much better than what you can find online through YouTube.
Thompson Seedless is not recommended for here for two reasons.
- It will only produce small round berries under natural growing conditions; a plant growth hormone (gibberellic acid) is needed to get the characteristic long berries you see in the store.
- The cultivar is very sensitive to powdery mildew. I could not access the pictures, but this can definitely cause the leaf symptoms described. It is not practical for a home gardener to spray for powdery mildew. Simply too many sulfur sprays are needed. So, it’s much easier to grow a more resistant cultivar like those recommended in the publication I link to above.
Fertilizer is not needed. Also, on well-established vines, not much irrigation is needed either. – Anne Schmidt, OSU Extension Master Gardener
WaspOSU Extension Service
Q: I have a flowering bush that bees absolutely love. Today, however, I noticed a huge wasp/hornet flying around the bush as well. It's unlike any other wasp or hornet that I have ever seen. This one is approximately 1.75 inches long and has an intimidating orange body. The bees seem unperturbed by this interloper. There must be at least 100 bees buzzing around this plant, as is the norm on a warm sunny day like today. Likewise, the wasp/hornet seems to be ignoring the bees. I was able to take a few photos to share with you to see if you could identify this species and advise whether it's any more aggressive/dangerous than other wasps/hornets. – Multnomah County
A: I think your concern is whether or not this is an Asian giant hornet. It is not. The coloring on the abdomen is incorrect. To ease your mind, OSU IPM center has put together an Asian giant hornet identification and comparison sheet.
Precise identification of insects from photos is difficult. However, your photo does look similar to a great golden digger wasp which in spite of its large size is not particularly aggressive. – Anna Ashby, OSU Extension Master Gardener
Leaf damage on yard plants. Is it a disease?OSU Extension Service
Q: Three of the plants in my yard are exhibiting leaf damage. The affected leaves are dry, brown and brittle. The damage concentrates on the south side of each of the plants. The plants are: cotinus, fernleaf false cypress, styrax. – Polk County
A: Let me take these plants separately, although they are all exhibiting symptoms indicative of the same issues. Cypress: Evergreen trees get brown needle tips when stressed by not enough water, especially during drought seasons. Here is a page from the OSU Diagnostic manual.
Cotinus: We have no diagnostic information on this species in the Pacific Northwest, because it is found most commonly in the South, especially the Southeast. Stressed trees often develop leaf spots, which, together with other factors, can lead to leaf death.
Styrax: This, too, has no OSU diagnostic material available. As explained here, it has no serious insect pest or disease problems.
The common denominator among these plants is the southern exposure of the damage. This is typical for leaf scorch, where the leaves dry out during constant sunlight penetration. That is why plants most susceptible to it are often planted as understory (shade) plants, rather than full sun. But the other theme is a lack of water. I suspect you have been providing no supplemental water, and the plants are reacting by drying up, especially the plant tissue getting the most sunlight. Watering more often – when the soil is dry at your second knuckle is a good test if you don’t have a soil water meter – will help with that aspect. They are probably too large to be transplanted into partial shade (styrax and cotinus), but water will help them get through summer. – Kris LaMar, OSU Extension Master Gardener
Creeping red sorrelOSU Extension Service
Q: I have this small purple weed in my yard in Woodburn, and so far I cannot seem to stop it from coming back. I have sprayed it with Ortho Weed Be Gone products and that seems to kill existing growth but it always comes right back. I also pull it but that only removes the leaves. – Marion County
A: This weed is commonly known as Creeping Red Sorrel or Oxalis and the species name is Oxalis corniculata. It is a common weed in nursery production in pots, but it can also be problematic in flower beds and as you are seeing, even the lawn. It is problematic to control because it is perennial and will develop a fairly robust taproot from which it can re-grow if the leaves are pulled off. The taproot in a well-fertilized and watered lawn will be fairly long and is probably best removed if you use a small digging tool suitable for dandelion and similar weed removal. This weed also spreads by stolons, above ground shoots that root where they touch the ground. So, the weed is commonly found in clumps.
If that were not enough, it also reproduces by seed in cylindrical pods, which forcibly eject the seed when ripe. So, you may be knocking back the existing weeds with the spray you are using, but if it has gone to seed in the past, it will re-occur when they germinate.
So, to manage this weed, encourage good turf vigor with appropriate watering, fertilizing and mowing. Scout the lawn regularly for the characteristic purple foliage and remove or spot-spray young seedling plants prior to bloom (they have small yellow flowers). It may take some time for the existing seed bank to be depleted. – Neil Bell, OSU Extension horticulturist
Subscribe to Oregonian/OregonLive newsletters and podcasts for the latest news and top stories.
The Link LonkAugust 16, 2020 at 09:09PM
https://ift.tt/3kJuTHw
Ask an expert: Thompson grapes may not produce well in home gardens, even with adequate care - oregonlive.com
https://ift.tt/3eO3jWb
Grape
No comments:
Post a Comment