Before sending the Consulting Arborists your question, check some of the previously asked questions and answers below for immediate help.

Bark and Trunk Concerns

Q: Our red maple has a tumor-like nodule growth the size of a baseball on its trunk. Is this a burl or gall? Should it be removed? Will it hurt the tree?
Tree burl

Tree burl. Credit: Ben Husmann

A clipping from a crepe myrtle covered in sooty mold from aphids

A clipping from a crepe myrtle covered in sooty mold from aphids. Credit: Jeff Moore

Emerald ash borer

Emerald ash borer. Credit: Debbie Miller, U.S. Forest Service, Bugwood.org

A: Galls can be caused by fungi and insects. Burls can be caused by stress or injury. On branches and stems, both galls and burls result in modified wood tissue due to excessive cell division and enlargement. Although peculiar, galls and burls will not harm the tree, while removing them could cause a tree wound that could eventually be harmful to tree health. Your best bet is probably to leave the growth alone.
Q: My crepe myrtle tree has an oil-like substance dripping all around the base, the leaves are wilting and the trunk has white stuff on it. Can you tell me what it is and what to do with it?
A: This is most likely an aphid infestation. Aphids — sometimes referred to as plant lice — are small, soft-bodied, sucking insects that feed on tree leaves. They tend to cluster in large colonies on new plant growth. Many aphids leave honeydew in their wake as they feed. This sticky substance is a medium for the growth of sooty mold fungi and can attract ants, flies and other insects. We recommend you treat the tree with a systemic insecticide containing imidacloprid or acephate as active ingredients.
Q: My tree has a green growth over most of it, which is changing the color of the bark. What can I do?
A: Your description sounds like lichens. They are unique organisms made up of a combination of fungus and algae. The fungus grows on the tree and collects moisture, which the alga needs. The alga creates food from the sun’s energy, which feeds the fungus. Lichen on tree bark — greenish-gray patches, typically one to three inches in diameter — are completely harmless to the tree itself since they do not penetrate or drain life from the tree in any way; they just grow on the surface for support.
Q: I have an ash tree that I planted 16 years ago when it was about three inches around. Now, it stands about 40 feet high, and the trunk is about 12 to 14 inches across. The problem is that the bark is splitting, and more and more branches are dying. What can I do to help save the tree?
A: Unfortunately, the symptoms sound like they are a result of emerald ash borer (EAB) and, if so, are fatal to your tree. EAB is an invasive, wood-boring beetle from Asia that has destroyed millions of ash trees and devastated tree canopy cover throughout the U.S. since it was discovered in 2002. The likelihood of EAB depends on where the tree is located, as the likelihood is highest in an EAB-infestation area.
Q: I have what I believe to be a scarlet oak tree in my front yard that will not grow leaves on one side. I think it may be a result of neighbors doing some sort of construction on their pipes about 20 to 25 feet away from the base of the trunk. I have no clue what to do, but I’m low on cash and can’t really afford an expensive evaluation. I’ve never dealt with these sorts of matters, but would really like to get my tree back to the healthy beauty it once was.

Scarlet oak

Scarlet oak. Credit: David Stephens, Bugwood.org

A: Oaks have straight grain wood. So if the side of the scarlet oak with damage faces the neighbor with construction, then it is possible that roots were severed. The tree canopy compensates by shutting down a percentage equal to the root loss. Roots will eventually regenerate and so will the canopy, but the dead branches will have to be pruned. You can also have a qualified arborist examine your trees — there is no charge for estimates.
Q: I was wondering if your tree expertise could help me answer a question about yarn bombing. I’ve found many blogs online written by knitters saying that doing this to trees and leaving them that way indefinitely has no ill effects on the trees, and that some trees even need to be shaded in this way to prevent them from being burnt by the sun. In your expert opinion, does yarn bombing hurt plants?

Yarn-bombed tree

Yarn-bombed tree. Credit: Ursula Murray Husted

A: Trees do not need to be shaded in this way (yarn bombing) to prevent sunscald. If the yarn is biodegradable, it will eventually decompose, in which case it will not girdle the tree. However, if the yarn does not dry out between precipitation events, then the damp yard provides wood-rotting fungi with a better opportunity to enter through the bark and damage the tree.
Q: Our Honey Crisp apple tree has had the bark skinned at the ground level by a lawnmower that got too close. How can we help it heal?
A: The tree will eventually heal on its own. To encourage good health, apply a slow-release, low-burn fertilizer to the soil and water the tree to prevent drought stress. Also, put a ring of wood chips around the base of the tree. This ring of mulch should not contact the trunk. It’s there strictly to prevent future mower injury.
Q: I have a large white pine, and lately it is suffering from wood borers. Is there anything I can do to save it?
A: Unfortunately, if the borers are already in the tree, there is very little you can do about the current infestation. However, to prevent additional borers from entering the tree, you should apply an insecticide to the bark so they will be unable to lay eggs in it. The problem could be more basic than the borers, though. Borers are most likely to attach to a tree that is already weak and stressed from drought or some other factor. If you’re able to reduce the stress factor to prevent a new infestation, the tree will likely recover.
Q: I have two willows that I planted in a wet area in my yard; they’re about 12 years old. Recently, they seem to have developed some sort of big holes in the trunk where the bark is missing. A lot of ants seem to have moved in as well. The trees keep growing, but now, one leans to the side. Is it the ants that are the problem? The holes? Both?

Willow tree

Willow tree. Credit: Geaugagrrl/Wikimedia Commons

A: The willows are probably suffering from wood-rotting fungus. The ants are not the cause of the problem, but have moved in because they like to nest in the moist wood. The fungus will probably not kill the trees, but you will not be able to free them of this problem, and they will continue to grow on a lean.
Q: I have an ivory silk that was planted in June 2008. I noticed this year that the bark started to peel off near the base. What is causing this? Is it something to be concerned about? Is there a particular treatment for it?
A: If the tree is able to callus around the injury, and if there is a strip of bark on the back of the tree that connects above and below the injury, the tree may recover. Without the connecting bark, the tree is unable to send nutrients manufactured in the leaves back to the roots. Eventually (in about two years), the roots will deplete their stored reserve, and if that happens, the tree is doomed. Sorry to offer such bad news, but unfortunately, there’s not much you can do.
Q: I have a large maple tree, about 40 feet and maybe taller. It is higher than my three-story house. The bark has started peeling off recently, but it is proceeding quite rapidly. What does this mean?
A: This question about your maple is difficult to answer because you don’t say what type of maple you have. However, it is characteristic of the sugar and silver maples (and to a lesser extent, the red maple) to shed bark. If you believe that your tree is not one of those species and can do your best to identify it, feel free to contact us again and we’ll do our best to help.

Leaf, Seed and Flower Concerns

Q: Our two maple trees did not drop their winged seedpods in the spring this year. Now, they are dark brown. Some are shedding leaves, while others are holding them on the branches. What could be the problem?
The fuit color of Norway maple, Acer platanoides, ranges from green to red, becoming tan and brown when mature.

The fuit color of Norway maple, Acer platanoides, ranges from green to red, becoming tan and brown when mature. Credit: Bill Cook, Michigan State University, Bugwood.org

Sprinkler

Credit: Tom Petit

A: A number of maples produce fruit that mature or hang on until fall and may persist into winter. They include Acer ginnala, Acer negundo, Acer palmatum, Acer platanoides, Acer pseudoplatanus and Acer saccharum.
Q: I planted two trees in my yard. One of them has yellow leaves now, and some branches have no leaves at all. The trunk is about four inches, and the tree is about six years old. We water them and have bark at the base to hold moisture.
A: The problem sounds like over or under watering. Both have identical symptoms: yellowing leaves followed by defoliation. Additional symptoms include wilted foliage, a sparse canopy of undersized or off-color leaves, leaf scorch and premature fall coloration.Dry soil conditions can significantly reduce the lifespan of your valuable landscape trees. A tree suffering drought can even be more susceptible to insect and disease infestation.Since most of a tree’s active roots are within the top 12 inches of soil, a good way to water is to put a sprinkler beneath the tree. Place a soup can close by, and run the sprinkler slowly until two inches of water has collected in the can. Be sure to water the entire root zone beneath the tree canopy. The best time to water is typically in the morning. Slow, deep watering every five to seven days during drought is ideal for mature trees. For young or newly planted trees, slow, deep watering every three days is a good gauge.When watering any tree, remember that the soil type and method of water delivery have a big impact on how successful the general recommendations might be. Trees planted on a slope may need some type of soaker hose or drip emitter, as applied water will run off. Sandy soils need shorter watering intervals, and clay soils should have longer intervals. Clay soils are hard to wet, and water will not infiltrate, but puddle if applied too quickly. The puddling of water may make one think sufficient water has been applied, but often, only the top inch may be wet. The depth to which water has infiltrated the soil must be checked by hand. It is always advisable to physically check soil moisture by hand to a one-foot depth instead of using watering intervals or relying upon automatic timers.
Q: I have two oak trees that I planted on the same day in 2001. One has prospered, has grown to great heights, turns green every year and has produced acorns the past two years. The other has not grown half as much, and the leaves turn yellow and pale green. The northwest side of tree has limbs that won’t sprout any leaves at all. How can I heal my tree?

The fruit of an oak tree

The fruit of an oak tree. Credit: Gary Kling, University of Illinois, Bugwood.org

A: This reminds us of the parable of wheat where some was planted in good soil and some was planted in rocky soil. One crop prospered and one didn’t. We think that what is happening with your trees is probably a result of iron chlorosis due to soil problems. Try adding chelated iron supplements to the soil if the tree is small, or through trunk injection once the tree is larger.
Q: I have a tree in our front yard that I believe is a maple tree. In the spring, sap was released from the tree. We noticed the sap on our vehicles. It appeared as if there was a fine mist of something sticky falling on the cars. Currently, the leaves are falling off the tree as if it were fall. Can you provide any comments regarding the tree’s behavior? Is it sick or dying?
A: The tree was not releasing sap, but the insects feeding on the tree were. It could be scales on the twigs or leaves or aphids on the leaves. As inefficient insect feeders, sap falls to objects below and is typically colonized by sooty mold fungi that turn the objects black. Have an arborist identify the pest and appropriate treatment timing. An arborist consultation is usually free and will confirm any issues. Then, you can decide how you want to proceed.

Apple tree. Credit: Liz West

Apple tree. Credit: Liz West

Q: I have a beautiful apple tree, but for a couple of years, it has not been producing apples. In the summer, the leaves die and fall off. What can I do?
A: The lack of fruit is most likely a result of the tree defoliation, so if you can solve that problem, the tree should produce fruit again. The defoliation could be caused by apple scab, which can be treated with a fungicide. However, if you live in either the Boston or the Seattle area, the problem could be the winter moth, which should be treated with an insecticide.
Q: I live in Benzonia, Mich., and this spring we had a simultaneous outbreak of tent caterpillars and another species, which devastated a large acreage of trees. My trees were bare by the time I could do anything for them. The leaves came back, but are smaller and thinner. What can I do to help my trees in the winter and into next spring if the insects return?

Eastern tent caterpillars

Eastern tent caterpillars. Credit: woodleywonderworks/Flickr

A: It sounds like you may have had an outbreak of gypsy moth as well as tent caterpillars. You can help your trees recover by fertilizing and irrigating now. In the spring, you can spray for the critters — the best time is just as they begin to break bud. It is a good idea to spray because if you have the pests several years in a row, trees will die. For the trees to put out the second round of leaves this summer, they need to dip into energy reserves, which will not be available to the tree next spring. Eventually, the tree will use up all its reserves and be unable to put out any new leaves.
Q: I was wondering if there is a disease of any kind wiping out Bradford pear trees in the Norfolk area of Virginia. Our tree wasn’t as full of beautiful blooms last spring, but we didn’t think anything of it until midsummer, when we realized the tree was losing leaves as if it were fall. I’m afraid the tree may be dead now. What could be causing this?
A: Your tree may be suffering from fire blight, a bacterial disease that spreads through pollinating insects. It usually begins where flowers are attached, then moves into the branch. When dieback occurs, it can make the tree look as if it caught fire. While fungicides may offer some protection, the severity of the disease can vary each year based on moisture levels. Additionally, pruning affected branches and sterilizing your pruning tool between each cut may also help.

Healthy Bradford pear blooms

Healthy Bradford pear blooms. Credit: Casey Fieser

Q: This is the first year that my Johnny Appleseed tree is bearing fruit. Is it common for the fruit to fall off prematurely, or is there something else going on with the tree that I need to address? There are some “rust spots” on some of the leaves, but I have not found any insects. I’m worried that all the apples are going to fall off before they mature. Do you have any suggestions?
A: Your Johnny Appleseed tree (and most fruit trees) will drop some fruit if it has too much to support. By self-thinning, the tree is concentrating its resources to ensure that it can take some to maturity. As for the rust spots on the leaves, that’s a condition that can be controlled by a spray applied in the spring.
Q: We have a large beech tree in my front yard, and I have a couple concerns about it. We have had a very hot summer, beginning in late June, and some of the leaves have started curling up, turning brown and falling in large piles. Could this be the result of extreme heat? The amount of falling leaves has decreased significantly now that the rain is more frequent and the temperature has become cooler. We just want to be sure there isn’t an underlying problem. Another concern is that the tree has quite a bit of gray and green lichen on the trunk. Is that a sign of bad health?

Beech tree

Beech tree. Credit: Peter Trimming

A: Many regions experienced exceptionally high temperatures this summer, and trees have certainly been affected. If the leaf drop was being caused by the heat, the tree will recover as temperatures get cooler. However, if you notice oozing from the trunk, it is possible that the tree may have beech bark disease. That disease can be potentially fatal, but if caught early enough, it can be treatable. Be sure to contact an arborist or tree care professional if such a symptom appears. The good news is that the lichen should not be a concern.
Q: I have a red maple tree that is about 10 years old. In late summer, it looks wilted, with the tips of the leaves brown and curling. It looks like this even if we have plenty of rain or if I water it. I had someone out last year to look at it, and he said it wasn’t diseased, but the other red maples in town don’t look this way. What could be wrong with it?
A: Based on the age of your tree, the problem is probably girdling roots. To correct it, you will need to remove the soil until you find which root is girdling another. There is likely more than one. Sever about one-quarter of the girdling roots each year until you have corrected as many as you can reach.

Root and Soil Concerns

Q: We have a large oak tree with an exposed root that runs across our dirt driveway. We would like to cut the root because it is a big bump to drive over, but we don’t want to kill the tree. Can we do this, and what is the best method?
Exposed root

Exposed root. Credit: Joseph O’Brien, U.S. Forest Service, Bugwood.org

Maple trees

Maple trees. Credit: William Warby

A: A large, healthy tree can tolerate the removal of a single root. Make a single, sharp cut through the root on the trunk side of the driveway. Let it dry out for several months, then excavate by hand to ensure the severed portion is not alive through root grafts. Water the tree to prevent drought stress.
Q: My neighbor has a garden on the other side of the fence. I have a maple tree 40 feet tall that did not come back this year; it has no foliage. Others in the neighborhood say that the lady in the back of my property may have killed other people’s trees and bushes with a nonselective herbicide. The tree is about 15 feet from the fence. Could she have put this herbicide on the roots and killed my tree?
A: A nonselective herbicide would have to have been sprayed on all the foliage of the maple tree to cause these symptoms. The active ingredient in major nonselective herbicides is deactivated by organic matter in the soil, so cannot be absorbed through the roots. Therefore, your tree is most likely suffering from some other issue.
Q: Can you recommend any publications specifically about tree roots: how they grow, recovery from damage, pruning, specific insect and disease damage, etc. — particularly for ornamental trees? We have problems with “street tree” roots under privately maintained sidewalks. The city forester says such roots can “fuse” with similar separate tree roots and therefore should not be severed or it could harm both trees. Is this true? Also, if the top five inches of a 10-inch diameter root is removed, will the remainder of the root allow the tree to survive?
A: A publication you might want to consult is The Landscape Below Ground II by D. Neely and G. Watson, 1998. As to your second question, yes, the roots can fuse. If you do decide to sever them, separate those closest to the least desirable tree. A root that has been cut to reduce its size could probably survive, but with the caveat that you provide extra water during the growing season (particularly during drought) for several years after the procedure until the tree can recover.
Q: What can happen to trees — pine trees in particular — when drain fields have been put all around them? Does it shorten the trees’ lifespans? Can the salts weaken the trees?
A: If the drain installation disturbed the tree roots, you will have canopy dieback in the same proportion (for example, if 20 percent of the roots were damaged, then, 20 percent of the canopy will fail). It is difficult to make an assessment of potential harm without knowing what type of drain it is. If it is a French drain or a leach field, the contents may have an effect on nearby trees. However, if the drain is a closed conduit, then, the damage will be mechanical only.

Tree Care Tips (Pruning, Water and More)

Q: I live in St. Louis, Mo., and I’d like to know if it is OK to trim dogwoods, Japanese maples and redbuds during the summer?
Japanese red maple

Japanese red maple. Credit: kloniwotski/Flickr

Mulch

Mulch. Credit: Eric E. Castro

A: You can prune trees at any time of year. Any time you prune, as a general rule, you shouldn’t remove more than 25 percent of the tree canopy. During the summer months, you shouldn’t remove more than 10 percent of the tree canopy. Some situations, such as pruning for safety, may alter these percentages a bit, but these are typical rules to follow.
Q: What’s the best mulch for your trees, and does it depend on whether it’s a fruit tree or not?
A: Crushed coconut shells are actually the best mulch for all types of trees because they retain their color, decay slowly and are crushed into small pieces for a fine texture. Walnut shells and cocoa bean shells are also good for these same reasons. Unfortunately, these aren’t always as readily available. Hardwood mulch, on the other hand, which is more readily available and is inexpensive, loses its color and decays very quickly.
Q: My tree is a red oak about 4.5 feet in diameter. A tornado came through and tore off a large limb, leaving a large wound on the side of the tree about 2 feet in diameter all the way to the ground. What can I do to help or save this tree?
A: Due to the severe nature of the weather incident and the potential safety hazards that can arise from it, we recommend you contact qualified arborists in your area to give estimates and perform pruning work (most arborists offer a free consultation). In the meantime, apply a slow-release, low-burn fertilizer to the tree soil and water to prevent drought stress.
Q: I have a dwarf peach tree and a dwarf cherry tree. I always have trouble knowing where and when to prune branches. The peach tree is two years old, and it looks great. I’m very happy with its growth, and I only use natural fertilizer and spray. Same with the cherry tree. However, when it comes to pruning for maximum fruit and best looks, I’m not sure what to do.
A: The best time to prune your fruit trees is in the fall, and you will get better fruiting results if you prune away smaller twigs back to a main branch.
Q: When it rains, my pine tree has what looks like soap or foam on it. Is this harmful for the tree?

Bubbles from spittle bugs

Bubbles from spittle bugs. Credit: Jerry Kirkhart

A: The foam on your pine tree is probably from spittle bugs. They live in a nest of foam “bubbles,” and when rain washes the bubbles away, they try to restore it. Spittle bugs are fairly easy to get rid of; you can wash them off with a strong stream of water. They will keep trying to recreate their bubbles to hide in, but eventually, they will be unable to keep up and will fall to the ground. You may have to hose them down for several days until you get them all.
Q: I have a spruce tree that is about 13 feet tall and has grown well over the last 10 years. It’s a bit shaded, but it does get some sun. Unfortunately, the bottom four feet or so are now all dead — just dead branches, no needles at all. It goes without saying that this is kind of an eyesore in the yard now. Is there anything I can do to bring this otherwise healthy tree (above four feet) back to full health?
A: Once dropped, those lower branches will not grow back, but it is natural for a spruce to drop some of its lower branches as it matures. Another possibility is that the spruce is infected with a cytospora canker. This is a fungus that causes branches to drop from the bottom up, and it is not reversible. If this is the problem, you may be able to see cankers around the base of the trunk. For more information, visit http://ohioline.osu.edu/hyg-fact/3000/3033.html.
Q: I live in Minneapolis, Minn., and many of my trees have had some trouble with worms this year. They are green/brown worms that hang down from the trees by a strand of silk. They also seem to be wrapping the trees with silk. The trees are mainly pines, but I do see them in my maples as well. We did have a large oak and one of these pines die last year from an unknown cause. I didn’t notice the worm problem then, but it could have been that. Any thoughts on what these worms are and if they are dangerous to the trees? Should I have them treated, or can I treat them myself?
A: The phenomenon of worms floating from a silk strand is called ballooning. Many insects display this behavior, so you need to determine the type to know how to react. Your best course of action is to take one of the critters to your county extension service for identification. The type of insect will determine the appropriate treatment.
Q: We planted some evergreen seedlings that are less than a foot tall. We are not 100 percent certain what species they are, but they look like spruce. They are not white pines. Their lower needles are browning, and I think they might die. Is there anything I can do? Is it a watering problem? How often should I water them?
Spruce needles

Spruce needles. Credit: Dave Hosford

Black walnut. Credit: Wendy Cutler

Black walnut. Credit: Wendy Cutler

Ginkgo leaf

Ginkgo leaf. Credit: Asela Jayarathne

A: Browning of the lower needles in your evergreen seedlings is an indication of a moisture problem — either too much or too little. Evergreens do not do well if the soil is soggy; an overly damp location will kill them, so keep this in mind when you tend to them. If the soil is not damp, the problem could be too little water, which you can supplement during dry spells.
Q: We have a large black walnut tree that was damaged during construction of our new house. It did not leaf out in the following spring. I believe the main problem was the soil added around it — maybe as much as one foot. Is there any chance this tree could recover in the future? How long should we give it before it has to be cut down? It is a little too close to our new house.
A: Because your walnut tree did not leaf out the following spring, it did not produce nutrients and will not recover. You should remove the tree as soon as is feasible. Although the dead tree can stand for four or five years, eventually decay and insect damage will weaken it structurally. If you wait until the tree is structurally weakened, it will be more expensive to have it removed because it will be unsafe for a climber. If it can’t be climbed, a crane may be required for removal — a much more difficult process.
Q: My three-year-old ginkgo tree stands at about five feet high and has plenty of leaves from about 3.5 feet down. Overall, it looks healthy, but the top is dead (about a foot to a foot-and-a-half). It’s been this way since spring. Should I leave it alone? Cut off the dead top? Hold a funeral?
A: The best course of action is to cut off the dead top. Most likely, one of the side branches will take over as leader, and in a few years, the tree will fill in the section that you’ve pruned out. Another possibility is that the tree had a borer that is working from the top down. That is not very likely, however, since borers don’t usually attach to ginkgoes.
Q: I have a ginkgo tree (approximately 200 years old) that has been dropping mature branches throughout the last year. Before that, a neighbor had pruned it incorrectly. We had an arborist look at it and then had it pruned by a professional. Is there anything we can do to save the tree? They told us it was old and reaching the end of its lifespan.
A: Though it’s tough to hear, the arborist who told you that your tree is coming toward the end of its lifespan is correct. To extend its life a little, you could fertilize and water the tree during drought periods. However, this will not prevent the tree’s natural decline.
Q: My Japanese maple has become too tall for its location. Can the tree’s limbs be shortened without too much damage?
A: Yes, you can remove the top limbs, but the tree will have the best chance for survival if you follow proper pruning practices.Here are some guidelines:
• Start the first cut on the underside of the limb a foot or so from the parent branch or trunk.
• Make a complete second cut slightly further out on the top side of the limb. This will allow it to drop smoothly, and avoid tearing the bark.
• Finally, make a clean cut to remove the remaining stub of the branch. When making this final cut, do it smoothly outside of the branch bark ridge and the evident collar, not flush to the parent branch or trunk. This allows for proper healing.
For help cutting very large limbs, or those high in your tree, contact your local arborist.

Tree Planting Tips and Species Recommendations

Q: Quite a few boxelder trees have grown up on our hill that runs down into a wetland. They are the only trees growing there except sumac along the edges of the woods. Should we let the hill remain just boxelder or plant another species of tree? We also want to plant native understory plants to make it a healthy ecosystem. The soil is a clay loam soil. Do you have any recommendations for what we should plant?

Sugar maple, Acer saccharum

Sugar maple, Acer saccharum. Credit: Bruce Marlin/WikimediaCommons

A: You want to create a miniature urban forest environment with a variety of trees so that they complement each other and so one single insect or disease doesn’t infest a single species.We would discourage planting additional boxelder because of the brittle nature of the wood and attraction of boxelder bugs. We recommend you retain as much sumac as possible. Try digging and moving some plants to other areas to start new colonies. Boxelder should be cut to a stump. Then, treat the cut stump with herbicide to prevent resprouting. Plant river birch toward the bottom of the slope where the soil is moist. Plant sugar maple or bur oak toward the top of the slope where the soil is drier. In a couple decades, when the top of the slope is ready for understory, plant ironwood or Amelanchier species.
Q: I would appreciate some advice on tree planting. I live in a small northeast town in Pennsylvania, and I’d like to plant some trees around my yard instead of building a fence. I am told that this is a bad idea because the roots could hurt the sewer pipes. Is this true?
A: For the most part, this is incorrect. A root cannot destroy a cast iron pipe, which is the type most commonly used between a house and city line. However, roots could be troublesome to a clay pipe. If you are concerned, check first to find out what type of pipes you have.
Q: We have a black walnut tree that has been in our yard for many years. Are the nuts safe to eat? If so, do we need to do anything special to remove the outside covering? Also, can you recommend a tree or trees that would be safe to plant near a septic system? Do you have any suggestions for trees with a tap root since they should pose less of a problem?
A: The black walnuts are safe to eat, but it is a messy process. The outer covering must be removed, but handling it will stain your hands with a difficult-to-remove and long-lasting dark color, so gloves may be a good idea. The inner, harder shell must be cracked to get at the meat. Yield of meat per nut is relatively small for the amount of work required to extract it.As for your second question, we can offer a list of trees not to plant near a septic system. Avoid planting silver maple, willow, tree of heaven, alder, mulberry, poplar, black locust or elm. In the juvenile form, nut trees (oak, hickory, walnut, etc.) have tap roots, but after about seven to 10 years, the tap evolves. Essentially, no tree that is more than 10 years old will have a tap root.
Q: My organization was recently given a small, grafted Johnny Appleseed tree. It is in a large pot while we wait to find a permanent spot to plant it next spring. While storing it in the pot, I am considering keeping it inside our museum for the winter and placing it on display. However, would it be best for the tree’s development to go through a winter freeze outside? Can I keep it inside for one winter or would it be best to put it outside?

Apple tree sapling

Apple tree sapling. Credit: David Masters

A: The tree will not do well in a heated indoor location. If you cannot plant it now, you should keep it in a place that provides conditions as close to outdoors as you can get. An unheated garage would be appropriate. Another option is to put the pot outside and mound leaves or other insulating materials around it to prevent the roots from freezing.
Q: I live in Houston, Texas, and we are looking for evergreen trees (not pines). We lost oaks during a hurricane and would like to replace them with trees that are more self-sufficient. The soil is mostly hard Texas clay. Could you suggest something that wouldn’t need constant care, but would stay green?
A: Other than pines, an evergreen that might work in your area is the Leyland cypress. They grow quickly, and can reach heights of 80 to 100 feet.
Q: I have some Douglas-fir trees and am trying to figure out exactly how old they are. Is there a rule of thumb for determining a tree’s age based on its diameter?
A: The most accurate way to tell a tree’s age is its rings. However, where this isn’t an option, we can use other factors to estimate the age. Because of heavy logging of Douglas-fir in the late 1800s, most of the trees growing today would either be less than 120 years old or older than that by centuries. If you check with local resources, you may be able to find out if your trees were missed by the logging. If so, this could provide a rough estimate of their ages.