Horticulture Guy

Q. How do I keep crows out of my cherry trees? I heard an owl decoy might work. Help?
Scott Landon - Surrey, B.C.

A. From what I remember from being a naturalist back in NJ crows will mob and attack raptors including owls. I found always found this fascinating since many smaller birds will dive bomb and attack larger birds that attack their young. I have seen sparrows going after blue jays, blue jays going after crows and then crows going after hawks. I have also heard from hunters that crows really dislike Great Horned Owls, which most owl decoys are created to simulate. So they use the decoy to attract crows when hunting them. So after the crows beat up your decoy they may just celebrate and knock back a few cherries. The best way to keep crows and other birds out of your trees is to use bird netting which is a black poly mesh (usually 5/8 inch openings) that comes in various sizes to accommodate different tree sizes. It can be cut easily down to size with a pair of scissors. It is draped over the tree and fastened at the trunk.

-- HG

Q. Is it a good idea to prune my Roses way back this time of year? I didn’t prune them earlier and they have a lot of black spot. I would burn the branches. Thanks Dottie Morris - Shelton, WA

A. Whether it is a good idea is debatable. Rose pruning seems to me to be part science and part art. Even dyed in the wool rosarians disagree at times on the finer points of pruning. Yes you can summer prune roses especially old roses ramblers that bloom once per year. They are flowering on the previous seasons growth so the recommended to prune these roses right after they bloom. Most remontant roses (have one major bloom period followed by sporadic spurts of flowering) can also be pruned after the first major bloom since flowers are produced on old and new growth. Although I have never seen recommendations for summer pruning hybrid teas they could also be pruned in the summer, but a drastic (as in “way back”) pruning will obviously curtail the plants growth. Part of the problem your roses may be having is reduced air circulation since you didn’t prune them this season. Another alternative is to selectively prune the shrubs heading them back to a few feet rather than “way back” and thinning to improve air circulation. Then cut out the diseased leaflets. The main branches will then send out new growth, which you can protect by following the guidelines I set out for Evelyn Moore in last week’s column. If you are interested in more info on more specific rose culture you may want to contact The Olympia Rose Society http://www.olyrose.org/ which is probably closer to you than the Puyallup http://www.puyalluproses.org/ or Tacoma http://www.tacomarosesociety.org/ Rose Societies.

A great product for insect and disease control on roses is Rose Rx 3-in-1

-- HG

Q. My peonies have good foliage, however the last two years they grow tall stems have heavy flowers that fall to the ground and don’t last long. Lora Fleener - Vernal, Utah

A. The flowers are not lasting very long because of their contact with the soil, which introduces soil microorganisms that begin to precipitate decomposition of the flower. Flopping (the unofficial term) is fairly common in many peony cultivars. I think the flowers have been bred so large and showy that the plants can’t support them without help. The solution is to support the peonies. There are various commercially available support loops, rings, and grids that can be used to support the peonies. Good ones are vinyl coated green so they are slow to rust and unobtrusive. Short stakes and twine can also be an effective alternative.

-- HG

Q. Black spots my rose leaves can you help? Evelyn Moore - Parkland, WA

A. It’s that time of year again. One of the problems with many of gardener’s favorite roses is that they are susceptible to a common fungus called black spot. The breeding of roses over the centuries rivals the plots of afternoon soap operas. Hybrids were made with roses from around the globe. The Mediterranean roses contributed to many modern roses being susceptible to black spot and other fungal diseases. This is because fungal diseases were at a major disadvantage in these dry climates so the roses didn’t evolve strategies to combat fungal diseases. I have heard ancestors of the Persian yellow roses tend to have the least disease resistance. But there are many good heirloom roses and Rugosa roses that have very good disease resistance. But since you are probably not interested in yanking out your prize roses and replacing them you will need to have a strategy to control the disease. First locate roses in an area that gets good ventilation or cross wind. This allows the surface of the leaves to dry more quickly after rainfall. Moisture on the leaves is needed for the development of fungal spores. So it follows that overhead watering should be discontinued or should take place in the morning keeping the amount of time the leaves stay wet to a minimum. In addition water is the vehicle that allows black spot spores to spread so splashing water only exacerbates the problem. Now that you have sings of the disease it is best to remove and destroy infected plant parts. Also rake up leaves that drop from the disease. This reduces the chances for future infections. Finally you may wish to maintain a spray regimen to further combat black spot. One popular home remedy was developed at Cornell University. Cornell’s baking soda spray consists of 1 tablespoon of baking soda (sodium bicarbonate), 2 ½ teaspoons of summer oil, a natural oil based insecticide used on plant, mixed with 1 gallon of water and sprayed on the leaves. The increased pH of the leaf surface seems to interfere with black spots ability to infect the leaves. Also Neem Oil has been now labeled for use beyond insect control. It now can be labeled as a miticide and a fungicide. You may see it marketed for the Rosarian as Rose 3-in-1. This is a good option if you also have the insect bane of the Rosarian the aphid.

-- HG

Q. I have a strange plant growing next to my walkway. How can I go about identifying it? Conrad Cinq-Mars - Gig Harbor, WA

A. That all depends on how strange it is. If your neighbor’s name is Seymour and he feeds it blood it might be Audrey II. I think it is doubtful that you have a Mean Green Mother from Outer Space though. But your neighbors might be a good place to start. Sometimes plants may reseed from your neighbors’ yard that you may be unfamiliar with. Another option is to bring it to the Pierce County Master Gardeners Plant Clinic. They are quite knowledgeable and should you truly have a strange exotic plant they will have resources like books and extension agents they can reference to solve your mystery. The Plant Clinic is open from 9am - 3pm weekdays, at WSU Cooperative Extension, 3049 S 36 Street, Suite 300, Tacoma WA 98409. Other parts of the county probably have similar programs through their County Agriculture Extension and Master Gardener Program.

-- HG

Q. One of our cedar trees has brown tips on the needles in one area of the tree. Both pictures are of different sides of the same tree. The brown area developed almost overnight about three weeks ago. We have not done any digging or grading in the yard from 15 years. I hope you might give us some idea of what might be causing this. Wayne Asplund – Bonney Lake, WA

A. From the picture you sent me I think what you are seeing is a fungal disease called leaf blight or tip blight. Our Western Red Cedar is a Thuja related to the Common Arborvitae so this disease can be seen on these plants as well. The fungus that is most likely to attack the Western Red Cedar is Cedar Leaf Blight or sometimes Kethia Blight (Didymascella thujina) one of the few diseases to be successful against these normally insect and disease resistant trees. The fungus overwinters on the needles of the trees or in the cast-off needles previously diseased needles. The spores start germinating in the spring during which time the fungus commandeers the needles resources (causing them to yellow) to produce more spores usually from late summer to early fall. You may be wondering why after all these years the disease has appeared. Most likely the trees became fuller as they got older and now there is less air circulation through the tree. Moisture is necessary for the fungal life cycle. Fungicides with fixed copperin them like COPPER DUST & SPRAY are appropriate for control. Since you have a large tree I would suggest you have a certified arborist take a look at the tree to verify that this is a fungus and to spray/treat the tree. The arborist may also suggest some judicious pruning to allow for better air circulation. Sometimes this disease is confused with normal fall leaf shedding, but since you have only seen these symptoms in the last week I suspect Cedar Leaf Blight.

-- HG

Q. My peach trees have leaf curl. All information I’ve been able to find indicates that there’s nothing that can or should be done once the tree has leafed out, but that when all the leaves have fallen off the tree (presumably in the autumn, although one of the two is dropping the most severely affected leaves already) it should be sprayed with a particular chemical (that I’ve been able to obtain from Lowe’s). Will it do any good to pick the affected leaves off right now? Should I do this? Can this problem kill a tree? Thanks for any help you can provide. Best, Steve Rodgers - Tacoma, WA

A. Well the fungal disease leaf curl has been the scourge of commercial peach growers in our area for years. Most commercial growers switched over to leaf curl resistant varieties like Frost. I am growing Q-1-8 from Raintree (a variety that kept its research designation – not a Star Wars droid), which has proven in my yard to resistant even in its youth (Frost can be affected when it is young but is resistant as it gets older). The recommendation is to spray fungicide during the dormant season since the spores overwinter on the bark of the tree. Then the spring rains move the spores to the new growing leaves. Once the spores have infected the leaves in the spring they cannot be treated. It would be helpful to remove any infected leaves now (in stages- so that the tree is not stripped of all its leaves at once) and any leaves that have fallen to the ground to reduce sources of new spores. Destroy the leaves (burning is best where allowed). In the short term the disease will not kill the peach tree, but it can weaken the tree leaving it open to other problems as well as reduce peach production. Be ready next dormant season so you can catch the disease in time.

-- HG

Q. I have two Wisterias, outside of the apt., I just moved into. They are growing from each side of a overhanging trestle When is the best time to prune them and how? Thank you Donna Beets - Upper Lake, CA

A. Prune them immediately after they finish blooming. This is to ensure you don’t remove next year’s flower buds.

-- HG

Q. Will it hurt evergreen trees to put woodchips around them as mulch if the chips are from recently chipped up trees and branches (green)? Bob Heacock - Harleysville, PA

A. Over the years there has been some controversy over using fresh wood chips as you describe in the landscape. The issues of soil nitrogen depletion from the mulch, disease transmission from the source material, oxygen depletion have all been raised when using fresh (not composted or aged) mulch. Most current though in the agricultural extensions and colleges indicates that nitrogen depletion from fresh mulch only affects the surface of the soil where at the mulch/soil interface. This means that established plants that have extensive root systems below the soil surface will not be affected. Disease transmission is rare, especially if you use hardwood mulch (from deciduous trees) on evergreen trees, as is in your case. If you know the source of the recently chipped trees and branches to be disease free then the chance of this being an issue is remote. The thickness of the mulch would need to be quite deep to prevent gas exchange between the soil and the atmosphere above. If you are mulching within normal ranges of 2-4 inches this will not be an issue. So I would say that your evergreens would benefit from the fresh mulch.

-- HG

Q. Why has my photinia hedge of 20 years losing it leaves? They are turning brown, curling up and falling off.
Barry Christensen - Puyallup, WA

A. Well twenty years is a good run if this is the first time you have had problems with your photinia. Leaf drop is occurs in the advanced stages of blackspot fungal infection. This is due to the presence of the fungus and suitable environmental conditions. Hedges are more susceptible because the act of shearing causes dense growth which decreases air circulation. Don’t trim the hedge during the summer months since young leaves are more susceptible to infection and the summer is when the temperature favors the fungus. Also irrigation systems that wet the leaves are also contributing. Remove all the leaves that drop off and dispose of them. In addition to these cultural changes you may also need to hire a certified contractor to spray the hedges with an appropriate fungicide like neem to get the disease in check.

-- HG