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Hortiscope

Ron Smith answers reader's questions about the world of plants and gardening.

By Ron Smith, Horticulturist NDSU Extension Service

Q: My husband bought me blue and pink hydrangeas a few years ago. I had blooms the first year, but none since. The foliage is beautiful and in great shape. I am assuming they are planted in too much sun. The plants do not get a lot of shade, so I'm thinking about transplanting them to an area that gets some afternoon sun. Will they bloom next year if I do this? (Warren, Pa.)

A: I cannot guarantee they will bloom if you move them to a new location. There are many varieties of hydrangeas. All of them should bloom in the sun or partial shade. In North Dakota, we have the Annabelle hydrangea that blooms in sun or full shade on the north side of a house. You need to find out what specific variety your hydrangeas are and follow the cultural practices for them. Blooming often is tied to what growth the flowers are produced on, such as old wood from the previous season's growth or from the current season's growth only.

Q: We planted a corkscrew willow last year that did really well. This year, it seemed to dry out while we were on vacation. We trimmed off some blackened shoots and watered it. It came back fine, but now the top foot of the main leader has turned black and lost its leaves. A large branch on one side also turned black. Can we prune it and hope for the best? (Atlanta, Ga.)

A: That is about all you can do in your area of the country. A branch fungus is causing your problem. I suggest visiting a local garden center to find out what fungicide you should use to get rid of the problem.

Q: I accidentally watered my garden for almost six hours! Is there anything I can do to minimize the damage? I plan on adding some calcium to the soil so my fruit doesn't rot from too much water. (e-mail reference)

A: There isn't much you can do. Tie a string around your finger the next time you turn your water on so you won't forget to turn it off!

Q: This year's rabbit population has decimated my hosta plants. Is there any chance they'll come back next year? (e-mail reference)

A: If you can keep the rabbits away for the rest of the season, there is a good chance the plants will recover. Once they are established, hosta plants are pretty tough.

Q: I have a question about a rubber tree that I've had for three years. It lives next to a window and has been doing great. However, I went on vacation for two weeks and left it on my screened porch for my neighbor to water. When I came home, all of the branches were drooped over the side of the pot. I immediately propped up the branches and returned it to its usual location. It is growing new foliage and appears healthy, but the branches continue to droop if I remove the props. Will my beautiful tree ever recover? (e-mail reference)

A: I don't know what happened to cause the lateral branches to droop. Propping them up will make it worse. As long as the plant is showing new growth, I don't think you have anything to worry about. I suggest cutting the drooping branches back in steps to see if they will hold steady. If the branches still droop, remove them completely. As new growth progresses at the top, nip out the terminal bud to get new, lateral branches growing lower on the tree. This is the best advice that the doctor can offer at this point! Whatever you do, don't overfertilize or overwater in an attempt to push the plant. Just follow normal cultural practices.

Q: The garden area where my bleeding heart is planted is in desperate need of compost because the ground is very hard. I would like to dig up all my plants and till in compost around the first part of September. I realize the best time to move bleeding hearts is after they are through blooming. (Fargo, N.D.)

A: Do your work this September. You probably will not sacrifice anything in the process if you apply normal care in handling the plants.

Q: I live in southeastern Pennsylvania and just planted eight arborvitaes. Someone at the nursery that sold me the plant said that arborvitae require 10 gallons of water per day during the first summer. That sounds like a lot of water to me, but I’m not much of an expert. Would you happen to know? (e-mail reference)

A: I just came back from eastern Pennsylvania where I was visiting my 92-year-old mother in Doylestown. While the soil is not high in clay, it isn't pure sand, either. The soil would have to be pure sand if you were going to apply 10 gallons of water a day! In a nutshell, that's too much water. What I would suggest is spreading organic mulch over the planting area to keep the soil moist, which is all that is needed. Then use common sense. If you have several hot, windy days without decent rainfall, then give them a good soaking two to three times a week, but no more. They should do just fine under that watering regime.

Q: I have a cascade prairie willow tree in my yard. It has been there about a year. This year, it is starting to get some black branches on it. Does this mean it has a disease or should I just trim the branches off and let it grow? I also am wondering how this will affect our yard and how fast the tree will grow. (e-mail reference)

A: This probably is a fungal disease of some kind that is common on willows. Prune the branches as the black branches show up. Willows grow fast, so I hope you gave your tree plenty of room to spread out. Willow problems usually do not impact the surrounding plant material.

Q: My husband and I want to add wildflowers to our lawn. What is the best way to learn about wildflowers, such as what looks good together and how to plant them? (Bismarck, N.D.)

A: Add wildflowers to your lawn? What will you do about mowing? Are you going to cut out parts of your lawn and replace it with beds of wildflowers? I assume the latter. Your best bet is to go to a nursery in Bismarck and talk to someone who can advise you about what will grow best in your location. Most wildflower mixes are customized for sunny, dry, shady or moist locations. The best time to get them started is in late summer or early fall. They will germinate quickly in the warm soil and have fewer weed problems than if you did the same thing in the spring. The following spring, your planting will be awash with beautiful flowers! They are good attractants for honeybees, butterflies and hummingbirds.

Q: I have a question about thatching a lawn. The lawn has 1/2 inch to a little more than an inch of thatch. What can I do to lessen the amount of thatch in the lawn? Can I do anything this year or do I have to wait until next spring? (Fargo, N.D.)

A: Late summer or early fall is the best time to do lawn renovation work in North Dakota. I would suggest a core aeration followed by a power raking. Overseed the area and give it a shot of winterizer fertilizer, which just means that it is lower in nitrogen and higher in potassium.

Q: We moved into a house (southern New Hampshire) last year that had four grape vines that were very small. There wasn't much growth last year and no sign of grapes. This spring they started out small, but now the vines are roughly 7 feet tall and have huge leaves. However, there is no sign of grapes. About a month ago, I thought I spotted some tiny clusters of grapes, but they have since disappeared. Is it possible that the soil is too rich in nutrients so the plant can't produce fruit? I'm not sure what to do at this point. I'm not fertilizing the plants and all they get for water comes from rain, but their growth the last few months has been incredible. Ideally, I would like to get fruit and not just have huge plants. (e-mail reference)

A: All you can do now is try to keep them from becoming the Kudzu of the North. Prune them back to a manageable size and keep them there. Most likely they are beta or valiant grape varieties, which are hardy and vigorous. These varieties make good grape juice and half-decent homemade wine. They eventually will produce grapes. I have a valiant in my backyard that does the same thing. The plant keeps me in shape with the pruning, but we get decent grape production without even trying.

Q: I have a problem that needs to be solved. I have a large evergreen that is in need of trimming because it hangs over our deck. I need to be able to seal off the branches that I need to prune back; otherwise, the sap will drip on the deck. Does anything seal the ends? (e-mail reference)

A: Nothing will seal it up except time. The wounds will compartmentalize and then stop dripping. In the meantime, I suggest placing a cloth or pans where the dripping is taking place on the deck.

Q: I've read all the material on your crab apple Web page, but I still need help. I had a local nursery plant a thunderchild in my backyard (facing south) in June. It's been a very warm summer, so I was watering once a week. It was looking very dry, so I started watering it every evening for 15 to 20 minutes. It now appears that there is a white dust type of coating on the tree. I also noticed a bit of blotchiness on the leaves, but I'm not sure if it’s a disease or because it was so dry. (e-mail reference)

A: Thoroughly watering once a week should have been enough unless your soil is almost completely sand and your part of the country has been getting hit with 100-plus degree heat and rainless days. I suggest getting back in touch with the nursery that planted the tree for you. It sounds like the tree has powder mildew fungus and is starting on apple scab development or some other leaf spot fungus. The nursery is in a better position to assist you with your particular problems and should stand behind the tree it sold you.

Q: My question concerns a bur oak that the city planted in my front yard this spring. There is a gas line a foot away. I phoned the gas company to let it know about the situation. However, the person from the company told me there's nothing to worry about. From your experience, do you think there will be a worry down the road? Also, a co-worker told me that bur oaks, once they get going, can grow so fast that the bark can split. This tends to happen in our area (Ontario, Canada). Have you heard of this happening? How can I prevent it? (e-mail reference)

A: You have nothing to worry about, at least from the tree. As for the bur oak bark splitting, it rarely happens if you wrap the trunk every fall before winter arrives. Do that until the trunk begins to get corky. To further prevent this from happening, don't fertilize unless the tree shows deficiency symptoms. Most trees planted in a landscape setting do not need fertilization on a regular basis. The nutrient level of most soils is adequate for healthy growth.

Q: I was given a very nice begonia, but do not know what kind it is. It has large, waxy, deep green leaves and small, pink flowers. It has been hanging outside all summer in full to partial sun and is doing well. I want to know if I can plant this in the ground. If I do, will it come up again next year? (e-mail reference)

A: Only if you live in a frost-free area of the world will it survive through the year. Otherwise, you must dig it out of the ground before killing frosts arrive. Allow the plant to dry, store it during the winter months in a cool, dry location and repot it in the early spring for replanting outdoors when all danger of frost has passed.

Q: This spring I transplanted some young cottonwoods from a nearby lake. Some of them now have bark opening up on the trunk. It looks like some kind of canker, but no sap is coming out. It there something I can do to treat this problem before it affects the tree? (e-mail reference)

A: This is due to the fact that the trees were removed from a sheltered area and planted in the open with their thin bark exposed to the elements, especially the winter sun. The tree usually heals on its own. However, I would recommend wrapping the trunk every fall before winter arrives to provide protection until the trunk develops a corky bark in a few years.


NDSU Agriculture Communication

Source:Ron Smith, (701) 231-8161, ronald.smith@ndsu.edu
Editor:Rich Mattern, (701) 231-6136, richard.mattern@ndsu.edu
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