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Don Kinzler, Published July 27 2012

Hortiscope: Patience required with dwarf tree

Q: I bought a dwarf Valencia orange tree about two months ago. Since then, it has not grown an inch. I had transplanted it into a 1-gallon pot and put it in the middle of my dining room table. (email)

A: You sound like an impatient person. A dwarf orange isn’t going to surge into new growth anytime soon. As long as the plant is healthy, with foliage remaining and a normal green color, you should be happy.

When the plant has accumulated enough carbohydrate (photosynthates) energy to do so, it will produce some new growth. It may be that you have it in too low a light situation. If so, move it to where it can get some direct sunlight. If that isn’t possible, then provide artificial light from a plant light for 12-plus hours a day. During the next six to nine months, you should see some new growth taking place.

Q: I read with keen interest your responses to the questions about spruce trees, so I thought you could help us with a spruce issue. We have a cabin in a spot that is very sunny and generally dry during the summer months. In front, there is a long, tall, man-made mound. The soil in the mound is somewhat rocky but of reasonably good quality and it drains well.

We planted some blue and Colorado spruce trees four years ago for screening and installed a drip irrigation system. Since then, we have replaced several of the spruce because many turned yellow, then brown, and died. Several of the trees still have a yellow cast, so early this June, we began ramping up the irrigation rate.

We now irrigate every night for 10 hours, giving each tree a total of about 1 to 2 gallons per minute at two points of the drip line. They seem to be improving and are putting on new growth. My concern is that we are watering too much. No water pools on the mound because it drains easily into the soil on the mound.

Also, what’s the prognosis for these trees? Are we going to have to water them forever? (Lake City, Colo.)

A: Well, they won’t win any beauty contest. Keep in mind that the roots will follow the percolating water through the soil (or stone) profile. Eventually, the roots should reach a site where there is a reservoir of moisture sufficient enough to sustain these trees through normal rain cycles.

After this growing season, they should be able to grow and thrive on a heck of a lot less water than you are currently supplying. You are growing them hydroponically at this point, so they need to be weaned gradually through the remainder of the summer to less and less water. At most, you can soak the trees two to three times a week for three to four hours at a time.

Q: I have a client who brought in some plums that have worm damage. I believe pectin is coming out of the plums. He sprayed them with a fruit insecticide (he couldn’t remember the name) during blossoming, but they are starting to fall off the tree. This also happened the past two years, so that is why he sprayed this year. Is there anything else he can do? (email)

A: These plums have curculio damage. Pick off and pick up any plums that are showing any evidence of this activity. Absolute sanitation is a must. Rake up all the fallen leaves and fruit in the fall. Spray the tree with dormant oil in the early spring before bud break and then spray again with Isotox or Malathion at bud swelling. At petal drop, spray the tree with Sevin and again two weeks later after all the petals have dropped. He also can place pheromone traps in the tree. The traps will keep the females from being fertilized and reduce the incidence of larval damage.

Q: I found your email address on a website about Christmas cactus. Are you able to offer some advice? I live in England and have a little cactus given to me as a present three to four years ago. It blooms very well and is growing well. It has been repotted once. However, it has developed tiny spots on some of the new- growth leaves. They look like raised pinpricks and are yellow in the middle.

Some of them have turned a dark purple. My cousin thinks I should break off the problem stem. However, I would lose about one-third of the plant. I have done a lot of searching but cannot find anything remotely similar to this problem because of the size and color of the spots. Thanks and hope you are able to give a bit of advice. (email)

A: Usually fungal or bacterial diseases cause sunken areas in the foliage. This could be an insect that goes after the more tender new growth, such as scale.

I’d suggest that you use alcohol or a dishwashing soap water solution. Wet a rag with one of these and see if the marks wipe off. If they do, then the problem should be solved. Be fastidious in getting after these spots as soon as they show to keep a new generation from arriving. Otherwise, I have no further suggestions.

Q: I have two young weeping pussy willow trees that I planted this spring. One tree’s tips turned hard and brown. What does this mean and what should I do? Thank you. (email)

A: Unfortunately, I have nothing to tell you about what happened to your weeping pussy willow, other than those tips are probably dead. I don’t know of an insect or pathogen that would damage just the tips of these plants. All I can guess is that it must be some sort of an environmental impact such as a late frost last spring.

Q: I have a small raspberry patch that it is getting so many thistles and another weed that has leaves from the very bottom to the top. I try to keep them pulled, but it is impossible this year. Is there a spray that I could use that won’t harm the raspberries? Maybe it is best to dig it all out and forget the berries. (email)

A: Nothing is worse than thistles invading a raspberry patch. If you feel overwhelmed, I’d suggest digging the entire patch out and do a clean cultivation for the rest of the growing season. Assuming success with this endeavor, you can replant with raspberries or a different crop. Berry picking is over for this season, so you can get in there now on a relatively cool day. Any thistles or other weeds that show after can be nuked with Roundup.

Q: My question is related to poplars. I had one pop up three years ago in a very wet area around my house. Back then, I didn’t know what it was, but it seemed like a nice tree, so we took care of it. Three years later, it is a very nice tree that is almost 15 feet tall and its leaves look amazing. We cut some lower branches last year and left some clippings on the ground. One of them took root and grew. A year later, I moved it to the backyard. We like their leaves and the fact that they grow so fast to bring us shade. We were planning to plant a few more. However, I am having doubts after reading through your Web page on poplars. Our property is not large, so the tree would be fairly close to our house. Should we keep the two that we have? Should we add the other two we were planning to plant? What other fast-growing trees would you recommend? (email)

A: I advise you to keep tabs on these two trees to be sure they don’t start getting ahead of you as far as care goes. As long as you can, keep them properly pruned and monitor or prune the roots that may be going in the wrong direction as far as you are concerned. Beyond a point of reason and common sense, you then need to get the proper care turned over to an International Society of Arboriculture certified arborist for annual maintenance pruning. I planted a couple of quaking aspen in my swampy backyard when I moved to Fargo. Like you, I loved their rapid growth and rustling foliage sounds. However, they started getting ugly in many ways. There was branch dieback, poor form and invasive roots into our vegetable garden. I finally removed them and have been happy ever since. There are plenty of fast-growing trees to consider, such as northern acclaim honey locust, many cultivars of silver maples, hybrids of silver/red maples, Redmond lindens and cutleaf weeping birch. Your local garden center should be able to advise you on the best trees for your area.

Q: Any ideas on how to reduce or eliminate the flower and fruit production on a greenspire linden? I have been in my home for 17 years, but it is only the last four or so years that the trees have been so messy. The linden is right next to our deck. Is this a cyclical thing? (email)

A: This problem often is cyclical in nature. The mess could be minor in some years, but a bad mess the next. There are sprays that can be applied but they are not practical for shade trees such as lindens. Timing is extremely critical and the results are variable at best, so it is not worth the investment or trouble to attempt controlling the problem. The good news is that the mess should be ending soon.

Q: I have two spruce questions you may be able to help with. I planted a hoopsi spruce in 2007. Five years later, it’s at least 15 feet tall and just gorgeous.

However, its lowest branches are on the ground, so I’m concerned that their periodic contact with wet ground puts them at risk for disease. Should I prune off these ground-level branches or is contact with the ground not a problem? I also have a hoopsi that I planted last year. This spring, it was attacked by bagworms. After I noticed the problem, I sprayed with an insecticide that killed off the bagworms. The defoliation hadn’t advanced too far. A few of the branches in the tree’s upper third were stripped bare, but most still showed about 50 percent healthy needles. The other 50 percent of the needles are turning brown.

I’m wondering if these partially browned branches are viable. Will they continue to grow outward and eventually sprout new needles or should I assume these branches will die or become stunted? I’m not concerned about the needles that have been lost because the affected areas are close to the trunk. In a few years, those areas close to the trunk will be closed off from sunlight and lose their needles naturally. (West Virginia)

A: I’ve heard from just about every state in the country except West Virginia.

In another life, I used to travel all over your state as a salesman selling horticultural products. I would advise removing the lower branches to a point where you are satisfied and that good circulation can be provided. Some spruce purists consider such action an abomination of a perfectly symmetrical spruce tree. I think trees in a landscape situation need management pruning in this manner without destroying the symmetry of the tree. It certainly is a step in the right direction as far as disease and rodent protection goes. The other tree should recover from the ravages of bagworm damage. It is a credit to you for being alert enough to catch them early so that you could keep the tree from being totally decimated. Monitor it carefully in future years for their possible return.


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 email ronald.smith@ndsu.edu. For answers to general horticultural questions, go to http://www.ag.ndsu.edu/ndsuag/lawns-gardens-trees.