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Hortiscope

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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I bought a bunch of echinacea because they were selling for $1 a pot. Such a deal! My plan was to plant them now, but on the Web it says to plant them in the spring. Will they die if I put them in the ground now? (Hampstead, N.H.)

A: Plant them now. They should survive and be there for you next spring. Spring plantings are common for most perennial plants, but most can survive fall plantings as well. They are perfectly hardy for your part of the country.

Q: I live in Fargo. How do I get my raspberry plants ready for winter? (e-mail reference)

A: Cut out the canes that bore fruit this season. I usually wait until a good frost has killed the mosquitoes, yellow jackets and other bugs before getting into this work. It is pretty good exercise and generates a lot of body heat. Next spring, cut the canes that will bear for you back to about breast height.

Q: Is there any way to stop a linden tree from producing suckers around the base? My 25-year- old tree has gone completely crazy. I try to cut back these suckers about every two weeks. However, there are several hundred of them, so it gets to be very tiring and frustrating. Will the tree stop producing suckers with age? I'm even doubtful about cutting the tree down because I may not be able to control the suckers. I've tried covering them, but they keep growing. (e-mail reference)

A: This can be a problem with some tree species. The decision is to put up with it recurring or cutting the tree down. There is a sprout inhibitor called “Sucker Stopper RTU” that you can get at most garden centers. The product is sprayed on the cut surfaces of the suckers. That usually stops any further growth for the rest of the growing season. A tree that suddenly becomes a suckering headache usually is indicating some kind of stress, such as root rot, borers or cankers in the trunk or stem tissue. The problem also could be anaerobic conditions in the soil for an extended period. This is caused by a change in the water table or an overland flood. If you do decide to have the tree removed, late summer or fall is not a good time. Wait until next spring after the surge of new growth has abated and then have the tree removed. There will be fewer carbohydrates left in the roots to cause sucker growth. You will experience some suckering, but less in number. Another option is to use undiluted glyphosate (Roundup). Pour it over the freshly cut stump. Drill three or four holes about 2 to 3 inches deep into the stump and pour the herbicide into the holes. Do this a couple of times a week until you start seeing the results on the suckers coming up in the lawn or garden. The material is translocated through the roots and will kill the tree completely.

Q: Slugs are destroying my tomatoes. What can I do about this problem? I would appreciate any advice you could give me. (e-mail reference)

A: Get the tomatoes off the ground if possible. Stake them to make it more difficult for the slugs to reach the fruit. Other options available include using diatomaceous earth, rock salt, stale beer in sunken pie tins, slug motels or poison bait. Some people swear that eggshells work, but studies at the University of Minnesota have proven otherwise. Eggshells slow the slugs but don't stop them. Another trick that some swear by is to take some hydrated lime and put a ring of it around your tomato plants. Be careful not to get any on the tomato plants. Make it a good inch or more wide and sufficiently thick. Theoretically, because of the soft, moist skin on the slugs, this will cause them to dehydrate and die. To date, I have not seen anything that would contradict this home remedy.

Q: I am planning to add on to my garage. The garage will be right next to our rhubarb plants, so I need to move them. They are the red variety and have produced very well for us. When is the best time to transplant and are there any special planting instructions that will yield the best results? A neighbor said putting horse manure in the hole before planting would guarantee good plants. Any advice? I also have an apricot tree that I want to move. Any special instructions to get good results? How deep will I have to dig so I do the least amount of damage to the roots? (Highmore, S.D.).

A: Delay digging as long as you can this fall, but move the rhubarb and apricot tree the day before work on your garage begins. Try to dig out as much of the root system of both species as possible. Forget about adding any fertilizer such as horse manure or otherwise. Have the new hole dug before moving the plants. Transplant going into the evening hours and place them at the same depth as before. Water in completely and don't fret over some wilting taking place. They likely will come back for you next spring without any problems.

Q: I have a question about onions. When can they be pulled and how do you handle them? When should I cut off the tops? (Fargo, N.D.)

A: Have any of the tops bent over on their own? This is a good indication that the bulbs have reached full maturity and are ready to harvest. Allowing them to remain in the ground for too long after the tops have bent over encourages rot organisms to move in and shortens their storage life. Curing is open for discussion because there are several opinions out there and all seem to work under certain conditions. Since you are a backyard gardener and not a commercial grower, lift the onions by pulling and lifting at the same time with a spade. Cut the tops and lay them out in a cool, dry location, such as a garage with good air circulation, for a couple of weeks. You can do the same thing in your kitchen, but it depends on how many onions you have. When "cured" for a reasonable time, they can be stored in a cool, completely dark location with decent air circulation.

Q: We have been living here for three years. The first year, our trees were full of plums and were very good. The last two years, we had many plums on the trees, but they start falling off early in the season and then start rotting. Could you please give me some advice as to what we should do? (e-mail reference)

A: This is usually the result of plum curculio activity. The developing fruit is attacked by small beetles that emerge from the litter under the tree. The beetles begin feeding on the leaves and fruit and the female lays eggs beneath the skin of the fruit. The grubs that hatch then begin to feed on the flesh of the plums. This causes secondary rot and often premature fruit drop. Once the eggs are laid under the skin of the fruit, no controls are effective. The best approach to solving the problem is using operating room cleanliness. Pick up all the fallen fruit and leaf litter this fall. Harvest and destroy any mummified fruit remaining on the tree. Next spring, begin a spray program after blossom drop using a product, such as Sevin, to eliminate any beetles that might have escaped your sanitation efforts.

Q: Can you tell me if I can eat plums before they are soft? I have a very big plum crop this year, so the branches are breaking because of all the weight. Can you stew the plums? (e-mail reference)

A: Two easy questions with yes being the answer to both!

Q: I have a three-clump paper birch in our south-facing front yard. The tree is watered daily with a sprinkler system. Early this summer, we noticed the top one-third of two of the three clumps has drooping limbs and leaves. It hasn't lost any leaves and they appear by touch to be healthy. The entire tree has a heavy production of seeds. Do you think our tree could be unhealthy? (e-mail reference)

A: Without a doubt, watering every day is too much for the tree and turf unless the tree is a weeping willow and the turf is on a golf course with a sand-based green. Back off or it may be too late to save the tree.

Q: Is it true that birch trees should be trimmed in August due to the spread of bronze birch borer? (e-mail reference)

A: Thoughtfully and frugally pruning in midsummer is done to avoid excessive sap flow that would take place in early spring. Overpruning stresses the tree and causes it to decline, which sometimes leads to death through the bronze birch borer. Think twice before pruning any branches on a birch.

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 ronald.smith@ndsu.edu.


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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