You asked and we answered! Below are the tree questions we received throughout the Virtual State Fair Ask the Arborist series. Answers were provided through a series of YouTube videos, or are answered below. Thanks to everyone who submitted questions and tried to “stump” the arborists!
Watch the video series above, you can advance to the next one in the upper right of the video
Pruning & Planting
Q: What trees are “native” to Minnesota, and are good at attracting pollinators?
Q: Is it really true that you should wait to prune until months ending in “er” aka Fall?
Q: I have a tree cedar wax wings visit every year, but that recently got severe wind damage. It has groups of leaflets and clusters of reddish-orange berries and is about 25-30 feet tall. I’d like to identify it so I can plant a new one (or two). Can you tell me what it might possibly be?
A: Thanks for your question! Without a picture the tree you described sounds like a mountain ash.
Q: My husband insists on planting twigs (trees that are like a foot tall) in our yard because he believes they grow faster than trees that are transplanted at 3, 4 or 5 years of age. Is there any truth to this?
Q: What do you recommend at the base of trees in your yard? Grass? Mulch? Ring them or leave them alone? I’m pretty sure rocks and those mat things aren’t good but defer to the experts
General Insects & Disease
Q: I’m wondering if our boulevard tree could have a pest like EAB? Its branches are thinning out. Or is this an ash tree at all? If I am suspicious, should I call the city, since it’s technically on their property?
Q: My willow tree is dying out over the summer. We watered deeply and weekly during the hot spell, but that didn’t seem to help. What do we do?
A: These issues can be difficult to I.D. through pictures. It could be insect damage of some kind or it could be a canker or form of blight. There could have also been damage to the roots if someone was gardening nearby, herbicide drift, or winter damage. I would recommend having an arborist take a look in person to get to the root of the problem.
Q: Is my tree dying? I noticed the brown about a month ago.
A: There are a few different issues with spruce trees, and most of them require using a hand lens in person to properly diagnose. The tree does look young and if it hasn’t fully established yet, could be suffering drought symptoms.
Q: Do ants living in a tree pose a threat? I see sawdust around the base of a maple tree in my yard and wonder if I should be treating it in some way.
Q: Is tree fungus harmful to the tree?
A: Chicken of the woods is a type of decay fungi which can hollow out trees and make them structurally unstable.
Q: We recently moved into a house and replaced a half dead tree. The remaining branches were in poor condition at best. We planted a new Autumn Spire Maple last year, which began this year well, and slowly half of it died as well. The remaining branches look in pretty poor condition. We are on to our last attempt and remember that when we dug up the first tree, the ground smelled like a horse barn…..very much like manure. It even attracted tons of flies. We are noticing the same smell after digging up our most recent tree. We are reluctant to put another in the ground, fearing the same problems. Soil conditions are 75% clay, 25% dirt with a gentle slope so drainage shouldn’t be a problem.
A: Newly planted trees can be finicky at times. Sometimes they don’t get enough water, or too much. Watering newly planted trees is best with a soaker hose left around the base of the tree for about 30 min or so every other day, and then gradually extending that time to 1-2 times a week for the first year. It takes trees about 5 years to fully establish themselves and recover from any severed roots or issues like that from transplanting.
That being said, with half the tree dying and the smell you described, I wonder if there isn’t something going on in the soil. Which can be tough to answer through email or online. I would definitely have an arborist come out and take a look to make sure there isn’t a busted sewer line or something else going on. They can also go over first year maintenance for newly planted trees in more detail. Tree Planting Basics
Q: I have an elm tree that is getting washed out by drainage from the surrounding landscape. Some roots are now exposed without bark. The hill is also washing away. If we shore up the tree with dirt and plantings do you think we can save it?
A: Without seeing the tree in question I can only speculate that filling back over the root should be fine as long as they didn’t dry out. Some surface roots are normal for trees. It sounds like you would want to put some plants along the hill to capture the flowing water and reduce erosion. I would recommend having a local arborist come out to take a look for a better idea, or talk with a landscaper to discuss good plants to help with erosion control.
Q: The squirrels are wreaking havoc on our trees. I pick up limb after limb on a daily basis from our oak trees. Will it stop or will our oaks and maple tree (where they have chewed thru the branches on it) suffer from this damage they continue to do. We have lived here for 20+ years and never have I seen the squirrels so aggressive. Help!
A: Squirrels can really do a number on trees, and it can be tough to say why. Maybe a nearby bird feeder has been taken down, or acorns were light this year so they are going for whatever is available. It is possible that they are gathering twigs for a nest as well in which case it shouldn’t last forever. Most trees can handle a couple years of some defoliation and if the tree is healthy (enough water, nutrients, mulched, etc.) the tree should be able to recover no problem. If it is really bad the only thing I could think of to remedy would be to talk to either a pest company or animal control that deal with squirrels, but I am not sure on how that process would go. Hope this helps!
Q: My 30 year old Nannyberry Viburnum (lentago) has recently developed a grey-white chalky substance in addition to holes & brown spots on its leaves. It’s losing some leaves, especially on the West side. I have a photo I could send if you provide an address. Thank you.
A: It sounds like your viburnum has powdery mildew. This is easily treated earlier in the year to protect the foliage from infection. You can treat on your own or have an arborist take a look.
Q: How can I protect my linden from Japanese beetles? Do I fertilize in the spring or in fall or both? Does tree spraying really help since the minute it rains it washes away?
Q: What the heck is this and is it killing my tree?!
A: Jeff Hafner answered this question while live on WCCO
Q: We have a 30 year old hedge of lilacs (40′ long) of several varieties and about four weeks ago we noticed the leaves of several of the trees in the middle of the hedge were turning brown and falling off. What is causing this?
A: Our arborist Nick Kantola answered this question in our Ask the Arborist series, check out his answer in the link above!
Q: I’m wondering if this really large pine tree can survive or if I need to take it down. Big bare spots in the middle but there was some new growth at the ends of some branches this year & quite a few pine cones at the top of the tree
A: Looks to be Rhizosphaera, a common disease for spruce trees. They can also get spider mites as well. There are preventative treatments in the spring, but the bare spots will not grow new needles. The tree (if treated) will only produce new growth from the tips and may fill in a bit, but probably won’t cover the bare spots.
Q: Spruce trees that start to turn red and are dead within weeks. Not all the same variety of spruce and not all standing next to each other. Some of the trees are about 30 years old and one tree is much younger.
A: My guess would be rust disease then. Take a look at this link from the U of M and see if it matches the description. We don’t get it as commonly in the Twin Cities as further north because the alternate host plants are not as common in the metro area. Treatment should be along the same lines as Rhizo with a few sprays in the spring to protect the needles. I would just make sure it is on the label if you are treating yourself, or talk to a local arborist who does plant healthcare.
Q: Several of my pine trees are slowing having the needles turn brown and the branches die. This happens from the bottom up over a period of years. Mainly this happens on the North side of the trees and eventually spreads around the tree. Anything I can do to save the trees from dying?
A: A common disease of spruce trees is Rhizosphaera, which is made worse by prolonged moisture and humidity. The north side is most likely staying wet longer than other sides since it is not getting the same amount of sun. You can also direct irrigation heads aways from the branches to reduce moisture. Fungicide treatments are available in the spring to protect new needles, but spruce trees will not have new growth in areas where it is already bare. You may want to have an arborist assess the severity of the issue and they may recommend pruning up some of the branches and starting a fungicide treatment in the spring.
Q: We have 3 mature maple trees in our backyard. On one of them, the trunk and bark seems to weep on the south side! What could we use to wrap the trunk with to keep bugs or pests out and any further damage to the tree? It has already cracked or split a bit on the south?
A: This is common with maples and other smooth barked trees. The south side is subject to heating from the sun and then cooling overnight. This expansion and contraction caused by the heat can make the bark crack. More often than not, healthy trees are able to seal up the wound and be fine. No wraps or anything is needed since this can trap excess moisture and cause decay fungi and rot to set in. Leaving it alone allows the tree to seal up and the wound to dry out.
Q: I have a variegated maple, the leaves are all drying up, it’s watered a lot. At the base of the tree there are 3 holes in the ground about the size of ping pong balls, any ideas?
A: Depending on soil it could be too much or not enough water. We recommend watering with a soaker hose for longer periods of time infrequently so that the water can percolate into the soil and if it is well established (5+ years) watering when the soil is dry if there hasn’t been a lot of rain. This helps establish a deeper root system. The holes almost sound like squirrels which are digging up holes to store food this time of year.
Q: My maple tree’s leaves are changing colors already. Is this bad and what should we do to make it better? We’ve already had you guys out for “vitamins”
A: It is common for some maples to get chlorosis, which is a nutrient deficiency of either iron or manganese causing the leaves to yellow, but have dark green veins. Even with fertilization the issue could be soil pH, or girdling roots restricting access to the nutrients. I’d recommend a consultation with an arborist. They will probably take a soil sample and inspect the area around the trunk of the tree to determine the cause. There are treatments available to remedy, but can vary depending on the situation.
Q: My maple tree has dead wood in the upper middle main trunk. The bark also has whitish splotches. What could this be? Is the tree dying?
A: Some maples (like silver maple) are notorious for just having a lot of dead wood and branches as they mature. White splotches sound like lichen which is a common organism that is found on all tree bark and causes no harm. If there are large sections of dead wood I would recommend having an arborist come out to inspect the tree.
Q: We have a golden maple but this year the leaves are falling off and have a rusty look along the veins in the leaf. These leaves are higher up in the tree.
A: When leaves start falling from the top, it usually indicates some sort of root issue, but the rusty aspect stumps me a bit. It could be mites or possibly the rusty appearance is from the leaves starting to turn colors but dropping prematurely which would lead back to something with the roots. I would recommend having an arborist come and take a look for a better idea. Maples commonly get trunk girdling roots which can limit nutrients to the canopy and cause thinning canopies.
Q: We have an ash tree with several dead/dying spots. At what point do you recommend it be removed?
A: If you are planning on removal we recommend doing it sooner rather than waiting. If it does have EAB, waiting until it is totally dead makes the wood brittle and unpredictable. This means crews will need to use larger equipment vs. climbing the tree and can make it more expensive.
Q: My Ash tree looks healthy, what happens if I don’t treat it?
A: Unfortunately, the tree will eventually get EAB. It’s just a matter of when. Depending on your area, populations may not be large enough yet, but if you like your ash tree I would treat now to get ahead of the pest. It is easier to keep a tree healthy compared to helping it recover from attack. EAB does its damage under the bark, so one year it could be fine and then next year it will begin to decline. We have a lot of helpful videos that describe the process in more detail in our FB video library.
Q: My marshal ash tree has not fully leaved this year. There is no woodpecker activity and the branches with no leaves are not brittle. What could the problem be?
A: It is common for ash trees to have bare limbs in the lower part of the canopy. Since they produce so many leaves they can shade out the bottom branches causing them to not produce leaves. If the tree looks healthy other than that, I would guess that is what’s going on. The tree could also be stressed due to location or drought stress. It also never hurts to have an arborist come out and take a look in person to know for sure.
Q: We have a 1.5 year ash hybrid that has Japanese beetles. Do we ignore them or treat the tree?
A: Japanese beetles are only around from early July to early Aug. You can treat the tree to protect it from damage. If you are treating your ash for EAB that treatment will also treat Japanese beetles for the first year.
Q: Our oak tree in our front yard has a vertical separation (it’s not a crack, it looks like someone took a tool and drew a line) down the trunk. Did it get struck by lightning or what would make this happen?
A: This is tough to say through messages and photos. I would recommend having an arborist come out and do a risk assessment on the tree to get a better idea.
Q: I think our oak trees may have oak wilt. How can I be sure and is there a treatment?
Q: I have about ten oaks(red, white, burr) on my property. Is there any treatment that can protect these trees from oak wilt. I’m aware of the high, low, and safe risk seasons for pruning. Are there any other preventative measures that can be taken, such as the treatment available for Emerald Ash Borer, which I have already received for my ash tree. Thank you.
A: The short answer is yes, oak trees can be protected with treatments of Alamo treated every other year much like EAB. We just posted a video on this not too long ago and you can see that here.
Q: We have a huge oak tree in our yard that lost a big branch in last summer storm. We were going to trim the tree of a few branches that are getting too close to the house for the last few years but didn’t get to it. The tree is dropping a lot of green acorns already. To me that seems early. Is the tree in distress and trying to heal and should we wait to trim the other branches back until next year?
A: Did you see the video we posted on the best times to prune? You can watch the video here
The best time to prune oak trees is in the winter when there is no chance of it getting oak wilt. This is usually between November and early March. It is very possible that the tree is reallocating resources to seal off the wound causing early acorn drop. It could also be due to a dryer summer than normal causing some stress to the tree. If you are noticing canopy thinning or other concerning issues I would recommend having an arborist come take a look to make sure there isn’t something else that is stressing the tree.
Q: We have a 5-yr old red oak tree. It’s been very healthy but this summer the newest leaves are brown, dry, and shriveled. Is this drought or a sign of soil problem?
A: It could definitely be drought. 5 years is about how long it takes for a newly planted tree to fully establish and if the soil drains fast and it hasn’t been watered (other than rain) it could be drying out. Things like adding a mulch ring and irrigating during dry periods can definitely help trees combat drought stress. As always though, it is best to have an arborist come out and take a look to know for sure. Hope this helps!
Q: We have a swamp white oak planted in 2000. About three years ago the top 1/4 produced stunted leaves, the past two years no leaves at all. It is in a low part of our yard, in heavy rain there is water that will drain in a day. Will it recover? Replace? Prune? Better spices for wet feet?
A: Swamp white oaks are usually pretty good at dealing with prolonged periods of wet feet. Others that come to mind are river birch or willows. If the whole tree hasn’t produced leaves in 2 years I would say it probably needs to be replaced. If it is only in the upper canopy it sounds like some sort of root issue. Maybe bad nursery stock where the roots were pot bound or something and now it is finally catching up to the tree. It could be caused by flooding and roots dying back due to lack of oxygen, but it is tough to say without being on site. I would recommend having an arborist come out to inspect the area and get a better idea of what’s going on.
Q: Can oaks only be trimmed in winter?
A: Ben Cooper answered this question on our Ask the Arborist segment, check out the video on when the best time to prune trees is through the link provided!
Q: When can I safely have my pin (white) oaks trimmed???
A: Ben Cooper answered this question in our Ask the Arborist series on when the best time to prune trees is, check out the video in the link provided!
Fruit & Flowering Trees
Q: What could the little black spots accompanied by holes be on my pear tree 🍐
A: There are a number of different pest and disease issues that could cause these issues with fruit trees. Unfortunately, we do not treat fruit trees, but the U of M extension office may be able to help identify and point you in the right direction for treatment.
Q: Our Apple tree hasn’t given us apples for 3 years and we have two pollinator trees for it in our yard. Any suggestions?
A: This could be due to a number of reasons. There could be a pest or disease that is stressing the plant causing it not to set fruit, or it might be lacking certain nutrients required. I would recommend having an arborist take a look, or sending a soil sample to the U of M extension office to check for any lacking nutrients in the soil. Also, if they are small trees, they do take a few years after planting to start producing fruit. This can vary depending on establishment and how old the tree was when it was purchased.
Q: We have a 3-yr old contender peach tree. It’s the first year with peaches (100+) but they have brown spots, hard flesh, shriveled in spots, and are not edible. What’s wrong?
A: The peach tree could be either a fungus or pest issue. We do not treat edible fruit trees, however, the U of M extension website is usually pretty good at identifying pests and more often than not can be treated.
Q: I have a lilac tree that has gotten quite overgrown. How much can I cut it back and when should I do it?
A: You can prune lilacs any time of the year. However, if you want to keep the spring blooms you should prune right after the flowers drop before they set their buds for next year.
Q: Our apple tree has several places where the ends of the branches (about 12″) have been dying off. It started early in the year. This is the first year I’ve seen that happen.
A: It could be a disease called fireblight. The ends of the dead branches can curl up like the end of a shepherd’s crook. There is a treatment, but depending on the type of apple tree we might not be able to treat if they are intended for consumption.
Q: Our apple tree (20+ yrs old) had many dead branches, some bark coming off those branches yet other branches still producing a little bit. Does that sound fatal? Should we be using special fertilizer on them?
A: It could be a disease called fireblight, or stress from another disease called apple scab. It is tough to say through email or photos and is probably best diagnosed by an arborist on site.
Q: I have a 25-year-old dwarf Mcintosh apple tree. I know it is in need of pruning (last time was 3 years ago). Every year there has been an early drop of fruit. Why does this occur and is there a means to lessen or prevent it happening.
A: Pruning fruit trees is generally recommended for the late winter or spring. Early fruit drop can mean that there aren’t enough nutrients or energy to produce the fruit fully. The other option would be a pest or disease causing early drop, but would be noticeable from brown spots on the fruit and leaves, or something to that nature. You could send a soil sample to the U of M extension office to check for any deficiencies in the soil and if you are pruning in the summer to fall timeframe you could be robbing the tree of producing enough food to fuel fruit production.
Q: I have a 30 – 40 yr old apple tree that has been losing leaves mid-summer along with small fruit. The tree looks fantastic in spring. Almost dead in late summer. Now 2 other apple trees are acting similar. People have told me either a fungus or rust. I do have cedar trees in the yard
A: Our arborist Patrick Anderson answered this question on Ask the Arborist!
Q: Have a plum tree that was planted last fall, the trunk wept. How does that affect the tree?
A: It is common for some smooth barked trees to weep, especially on the south side where ambient temperature may be cool, but the sun heats up the bark causing it to expand and contract with the temperatures. This can cause cracks which will then weep. Usually the tree will compartmentalize with no issue. I would recommend checking for any signs of insect activity that could also be causing the wounds and weeping. These if left unchecked could stress the tree out.
Q: We have a 3 year old Canadian cherry tree. Two years ago we noticed some of the branches looked like a seed pod and some were splitting. We were told it was black cherry rot, a fungus. We cut those branches out and sprayed the tree for the fungus. This spring the same thing happened but not as much. We cut the branches out and sprayed again. We were told this could kill the tree. Is there anything we can do to prevent this from happening next spring?
A: It sounds like black knot, which is a common fungus on many cherry trees. Unfortunately, it can be a tough disease to combat. Pruning and fungicide treatments are the best options and may take a few years to get under control. The U of M has some good information on timing of pruning and fungicide treatments.
Birch & Aspen Trees
Q: My Swedish columnar aspens have been attacked by ants and are losing leaves on the tops and any branch that is growing. black spots and leaves being eaten by mold? eggs? Options?
A: We recently just posted a video answering a similar question about ants in trees. This might help narrow down what’s going on. If this doesn’t quite fit the bill, it’s always a good idea to have one of our arborists come out and take a look.
Q: My river birch is dying in the middle. It appears to have a fungus on some branches. Can this be corrected?
A: If you are seeing dieback in the canopy it could be a few different issues like trunk girdling roots or an insect pest. If you are seeing shelf type mushrooms on the main trunk and dead branches, I would highly recommend having an arborist take a look to ensure it isn’t a type of decay fungi. Trees also have what’s called lichens on the bark which can be confused as fungi but cause no harm to the tree.
Q: We have a 5+ year quaking aspen that started leaning after a storm. The root is exposed under the mulch. Do you service the Anoka area?
A: If the tree has uprooted, it will most likely need to be removed. I would suggest having an arborist come out to assess the situation in person to get a better idea. We service some of the Anoka area.
Q: We have a river birch that we planted 12 years ago and it has done well every year until this year. It leafed out this spring, but lost many leaves early on, and the remaining leaves are very yellow. It is on the north side of our property and we have watered it thoroughly throughout the summer. Some of its upper branches are completely bare. What do you think is going on?
A: River birch can commonly get chlorosis, a nutrient deficiency of iron or manganese. This can be caused by either the nutrients lacking in the soil, pH at a level that the tree cannot take them up, or trunk girdling roots cutting off uptake. I would recommend having an arborist come out to get a better idea of what is going on with your tree specifically. There are treatments available, but will vary depending on your site conditions. An arborist will inspect the trunk and most likely take soil samples to determine the route of treatment.