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Ron Smith answers questions about flowers, trees, gardens and shrubs.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I have two huge cottonwood trees. This spring, they began to start oozing sap. It started with just a fine sort of spray covering everything within a 100-foot radius or so. Now it is coming down in full-sized droplets! The trees also have not stopped shedding cotton, which is creating a ridiculous mess. I can't mow, rake or burn it. It's covering my yard, car, deck and house. I'm at my wit’s end with these problems. Please tell me this happens once every very few years and it should stop any minute now. (email reference)

A: I could tell you that, but it wouldn’t be true. It sounds like you have a very bad infestation of mites, aphids, scale, borers or all of the above. I encourage you to get a certified arborist out to your place as soon as possible to see if the mess can be stopped without poisoning the entire neighborhood. The arborist may recommend taking the trees down because they might be in a state of decline, which usually is indicated by an onslaught of insect ravages such as what you are experiencing. Go to to locate an arborist in your area. Be sure to check credentials and insurance coverage before allowing any major work to be carried out.

Q: Our tomato plants have curled leaves that I think are caused by all the wet weather. I would like to know if it would be OK to take off the affected leaves or just leave them. (email reference)

A: Leave them alone because what you are seeing is a normal response with some varieties to the heat of summer.

Q: About five years ago, we had a large linden tree removed from our front yard because it was encroaching on our house. We also had the stump taken out. Since then, I have rented a small backhoe twice to remove roots that were sending out suckers. The second time, I drilled holes in the remaining roots that were too large to remove and poured a stump herbicide into the holes. In preparing to lay pavers for a pathway, I discovered that the suckers are back. These are tenacious roots! Do you have any suggestions as to how to get rid of this tree once and for all? (email reference)

A: Indeed, they are tenacious. Get a licensed arborist out there to treat the suckers with a powerful systemic herbicide. An arborist usually can use more potent stuff than a homeowner.

Q: I came across your brilliant website yesterday. Thank you for offering the resource. I've learned so much from reading your plum Web page. However, I can't quite get to a certain diagnosis based upon other plum-related posts. I have a Santa Rosa plum that was planted about six years ago. It has given us bumper crops for the last four years. I prune it each fall while the leaves are on the tree. It occasionally is attacked by aphids, but not this year. About once a month after fruit set, I give the tree a low dose of a Malathion-based pesticide. It has worked well to keep the fruit free from pests. We had an extremely wet and cool spring here in Idaho. It had many flowers this spring, but since leafing out, it has shown little vigor and many branches have died. One branch is alive and bearing fruit. There is sap oozing from multiple points on the wilted part of the tree. There also is sawdust on some parts of the tree. If you have the time to write back to give me some ideas or solutions, I would greatly appreciate it. If it cannot be saved, I need to know so I can plant a new one to pollinate my other plum tree. If it is contagious, what can I do to prevent the loss of the other plum tree? (email reference)

A: The tree has been discovered by borers. When that happens to the extent you discussed, it is like a bullet to the temple of the head. You need to have the tree removed as soon as reasonably possible. The wood needs to be debarked, burned or hauled away as far as possible. The best control is to get pheromone traps. The traps are available locally or at The traps will disrupt the life cycle of the insect. Another tactic is to spray with an insecticide that has a residual, such as Malathion, just prior to leaf opening. Finally, the best preventive is to maintain the best possible care of the tree by eliminating or minimizing the stresses of drought, compaction or unnecessary wounding.

Q: We moved into a new home in south Fargo about four years ago. Our sodded lawn was beautiful the first two years despite some serious vole problems. For the last two years, the lawn has had areas without grass or thin grass and the color of the lawn is not bright green. I've noticed that part of the lawn near the drain is lush. I presume that is because that area has received excess water. Much of the problem area of the lawn has a mat of old grass, so we may need to have it raked when weather permits. Would you please write or call to give us tips on steps I can take to recover my once lush lawn. (email reference)

A: Lawns are easy to resurrect. Rent or have someone core aerate your lawn and follow that with a power raking. I assume you have an irrigation system because you had it sodded originally. This will create a lot of duff that will require raking and removal. If you have it done commercially, expect to pay a heftier price to have everything picked up and taken away. Scalp mow the lawn and collect the clippings. Expect it to look terrible after this treatment. Get a good-quality seed mix that has at least 55 percent or more Kentucky bluegrass, some creeping red fescue and a touch of perennial ryegrass (10 percent). Irrigate frequently and lightly for about two weeks. Do that two to four times a day until germination is evident. Once germination takes place, water about three times a week for 20 to 30 minutes each time. However, it depends on natural precipitation. Going into the fall, have a winterizer fertilizer applied to toughen the young grass for winter stresses. Keep mowing as long as there is no snow cover. The last mowing should be a full inch shorter than usual (assuming a 3-inch cut) and collect the clippings. Next spring, when the grass is green and you’ve mowed at least a couple of times, fertilize the lawn. Fertilize again around July 4. Fertilize again sometime in the fall. If this doesn’t give you a green lawn to be proud of, then something is wrong with nature, the seed you purchased or just bad luck.

Q: My question involves early blight on tomatoes. I planted from seed for the first time. The plants are beautiful and bushy. The plants also have a fair amount of fruit. I have a raised bed and use drip watering. Sadly, I returned from vacation to find the plants afflicted with early blight on the lower leaves. I removed as many of the infected leaves as possible and sprayed the plants with Serenade, which didn’t help much. I then used Daconil, which seems to have halted the progression of the disease somewhat. I had the same problem in a different bed last year, which is why I used a new bed this year. I filled the new bed with 100 percent compost from a local garden center. I’ve used 100 percent compost in the past with good success. My potatoes on the other side of the house now have the same problem. Do the spores travel by air? Could the spores have been in the compost? Is it a bad idea to use 100 percent compost as the base soil? I admit that I did not mulch. I don’t have too many other places to rotate them into next year. Vermont summers tend to be humid with plenty of sun. However, we do get many thunderstorms. (Vermont)

A: Using compost is OK as long as the area has good drainage and the material that went into making it compost did not have any herbicide residue. Grass clippings are used often for composting after a broadleaf herbicide was used for weed control. This doesn't sound like the case with your problem. Another potential problem is the use of diseased plant material. If composting temperatures reach 140 to 160 degrees for a sufficient length of time, many of the pathogens are killed. If the temperatures did not achieve that level, then there is a very good chance some of the pathogens will survive and infect a new planting. I would like you to contact the Extension Service agent where you live. Go to to find an agent. The agent may want to test for high salts or nutrients and possibly evidence of pathogens.

Q: My sand cherry tree is shooting up runners all over the flowerbed. The runners are very hard to control. The runners that come up have green leaves instead of the purple leaves on the mother tree. Why is this happening and is there any way of preventing or controlling the problem other than to cut off the runners? Also, after I cut the runners, more runners shoot up from that cut. Would spraying the runners with Roundup kill the whole tree or just the runners? I haven’t tried that yet, but I’m getting desperate. (email reference)

A: Sorry to say that this is the nature of the sand cherry tree beast. It is wired to sucker, so there is nothing you can do to stop it completely. That is why it has value in a shelterbelt planting. If you want to continue the battle, get some Sucker Stopper RTU. Spray it on the freshly cut surfaces. No more sucker growth will emerge from that spot. You will need to do the same thing next year. My strong suggestion is to get every trace of this shrub dug out and replant with something attractive and nonsuckering.

Q: I live in central Alberta, Canada. About four years ago, I transplanted Colorado blue spruce trees from a tree farm. They did well the first year, but we had a dry summer and fall the next year. The largest tree lost many needles on the west side. This year has been quite wet, so all the trees have lots of new growth. However, the largest tree still is having problems. Are there ways to promote new growth? I also have a number of smaller white spruce trees that have long leaders. Some are bending over. Should I prune the trees so they grow straight up? (email reference)

A: The answer is yes to your last question on pruning. As to the dead needles on the shaded side of the tree, I doubt they ever will catch up with the rest of the tree because of the shading. Don’t get too carried away with the watering if you are having a wet summer. Irrigate enough to prevent drying out, but don’t allow the soil to become soggy. When in doubt about watering, wait another day.

Q: I hope you can shed some light on the flowering crabs planted in our yard. I am including photos for you to look at. On most of the flowering crabs, the leaves are very narrow and thin and filling out poorly. The trees with burgundy leaves are prairie fire crabs. Those with green leaves are Robinson crabs. The prairie fires are in a wetter part of the yard but only sat in water for two to three days at the most. Even so, the Robinson flowering crabs and some of the other varieties that did not sit in water look the same. Could it be that they are not hardy for the area? I’ve had them for three to five years. The last photo of the flowering crab has branches that are turning brown a branch at a time. The branches look like the moisture is being sucked out of the branch because they get dark and dehydrated looking. We have cedar trees on our property, but I don't think that they are causing the problem. The very last picture is of a red maple whose bark split on the south side of the trunk. Is there anything we should do about the loose bark? It's one of the prettiest trees on our farm, so we want to protect it if we can. If we were going to pull out the flowering crabs, which I am seriously considering, what would you recommend for a tree with a nice shape, is sturdy, disease resistant and wouldn't be so terribly slow growing. Should we consider red maples? We need something that won’t grow so tall. Thanks in advance for your answers. (email reference)

A: The poor crabs are in miserable condition. I don't think they will amount to anything you would be proud to have on your property. Go ahead and have them removed. Replace them in an area where the chance of standing water will not be as great. You may want to consider planting spring snow flowering crabs. These are proving to be very hardy in our area and seem to tolerate heavy clay soils and our miserable winters. Cut the loose bark on the maple back to where it is attached to the trunk with a pocketknife. Leave it alone after that. This will facilitate quicker healing and not allow it to be a hiding place for marauding insects.

Q: I bought a house where the prior owner had planted 22 poplars down a long driveway. The trees were causing the blacktop to crack, so we cut them down. Most of them were dying and ugly anyway. We also applied a systemic herbicide. However, I have to walk the road every three to four days to pluck out all of the suckers that are popping up. I read where you said Roundup would not work. What will work? If I just keep pulling up the suckers, when will the roots die on their own? (email reference)

A: That process will work eventually. However, I don’t know where or when I said Roundup wouldn’t work because it does work on suckering roots if they are not attached to a tree. It will have the same effect as you pulling them out. Keep in mind that you also will have a dead spot in the area because Roundup kills anything green it touches. You also might want to consider using something like Weed-B-Gone herbicide because the product will not cause any collateral damage on the surrounding grass. It has systemic action as well.

To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or e-mail

NDSU Agriculture Communication – July 27, 2011

Source:Ron Smith, (701) 231-7971,
Editor:Rich Mattern, (701) 231-6136,
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