Ask An Expert
Is there anything known about the “tipping point” or ways to predict native trees
decline due to drought stress? Most of our native trees and plants are drought tolerant,
but in recent years we have had longer periods of no precipitation, high temperatures,
big fire seasons, and have been seeing more symptoms of drought stress and other insect/disease
problems combining to cause tree death. This is in native forests and rural situations.
( inland northwest- montana, Idaho eastern Washington. Primarily ponderosa pine, but
some other species like doug fir and cedar also).
Sharon, Spokane, WA
Sharon, There is a tipping point, but it would be different for each species or forest
type and what you would measure to indicate whether this point has been reached would
vary. If the trees are coniferous evergreens then the best indicator may be how many
years worth of needles are on the tree. Severely stressed trees will often lose last
year’s needles before the next growing season is over. Also stem (trunk) diameter
growth is a good measure of stress. Slow growth is a sign of stress. Finally, susceptibility
to insect attack is a good indicator of stress.
November 29, 2017
Q: I live in Cottonwood Heights but am currently visiting friends in the southwest of France, in Toulouse. Here is a question you have probably never had before! In the north of Spain, in the Basque region, they make a walking stick from a wood Neflier (makhila is the generic name for the walking stick). Is there any equivalent of Neflier in the US?
Thanks for your help
A: Tom, Yes. Neflier is a French name for the genus Crataegus or hawthorn. The Spanish name is Espino. Utah has one native hawthorn – black hawthorn or Crataegus douglasii. I see it all over the place at fairly low elevations where there is some water. It is a muiltistemmed tree or a dense shrub, but some species of hawthorns are tree-like, and many of these are planted in Utah. To learn more about hawthorns go to our Tree Browser website at www.treebrowser.org.
October 3, 2017
Q: A cut aspen tree, with the stump still in the ground, is sending out a huge amount
of shoots. Can anything be done to kill the stump, outside of removing it? Can the
shoots be killed with some product? Help!
A: Judy, Not really. Just cut it down and spray triclopyr (e.g. Ortho Brush-B-Gone or Poison-ivy Killer) or glyphosate (i.e. Roundup) on the stump surface (it is better if the stump is freshly cut), and cut off any sprouts and treat their cut surfaces too. It may take several rounds of this until everything is dead.
July 7, 2017
Q: I have a Kentucky Coffee tree in my landscape. It was healthy last year, but this spring just as the leaves were emerging, it was hit by a frost (about 30 degrees F) which killed the newly emerging leaves. A few weeks later new buds had formed but as the leaves emerged they are deformed, almost looking like epinasty from 2 4 D (but no herbicides have been used and the tree branches as 6+ feet above the ground). All leaves are affected. All the information I find on the web indicates that the Kentucky coffee tree is rarely affected by pest or disease, but something is obviously wrong. I have included 2 photos of leaves. Do you have any ideas what is wrong?
A: John, I thought this was going to be a case of deformation due to frost damage of tissues still in the buds, but after looking at the pictures, I don’t think so. For one thing, the type of damage that causes usually does not include twisting like this. It is more small holes and bumps. Also it doesn’t make sense since new leaves produced after the original leaves were killed would be from tissues produced after the frost. So I am still thinking herbicide. 2,4-D can drift quite a bit, especially on warm days when it volatilizes. The amine form is the most common and is not as bad as the esters (there are low and high vol esters).
Some plants develop cancer-like growths on some of their tissues and these growths often involve flattening and twisting. Though this is not completely understood, it appears to involve genetic changes in the tissue in certain areas on the plant, and pruning off those areas gets rid of the abnormal tissue in that area. These genetic changes seem to be triggered by viruses, maybe bacteria and fungi, certain insects (forming galls), etc. I don’t know if frost damage could trigger this kind of thing. There is a good article on this in the NY Times at www.nytimes.com/2015/07/28/science/cellular-cheaters-give-rise-to-cancer.html. I have attached a picture of one type of such growth called fasciation, that involves flattening of branches. This one is on a juniper here on campus. I also attached a photo of some frost damage on a maple.
I recommend that you watch it and see what happens. It won’t spread to other plants and it may go away. There is nothing you can do about it, so you might as well let it go for awhile. If you do, please keep me informed.
June 29, 2017
Q: I planted the Bur in March and have been excited to see it leaf out. I have noticed that a good number of the leaves aren't the typical dark green that I've seen, and am attributing this to stress. That being said, the leaves are a mixture of light green to yellow/bronze. The veins themselves are still green and the leaves don't appear to be wilting so far. I've also read that this could be a sign of over or under watering the tree. I've attached a photo to better highlight what I am seeing. Any help you could offer to get this tree in good shape would be appreciated.
A: The leaves look perfect for this time of year. Many plant leaves have some red in them as they emerge, but before they mature. The chlorophyll that will absorb sunlight and use that energy (along with CO2 and water) to make food through photosynthesis is not fully mature at first, and the sun would bleach the chlorophyll without some protection. The red pigment is there to absorb that light and protect the chlorophyll until it can absorb light on its own and use the energy. Some trees retain the red pigment and are more-or-less red all summer, while with others it fades and the leaves end up pure green. Your bur oak will be the latter. In a cool, prolonged spring like we are having this year, the red may hang around longer since the development of the chlorophyll is delayed.
Q: When is the best time of year to plant trees?
A: Trees are best planted when they are still dormant with tight, unopened buds in the early to mid-spring after the soil has thawed. Cool temperatures and good soil moisture in the spring help trees get established. Fall planting also works well for many species, though watering is critical if the fall is dry. Summer planting of B&B (balled-and-burlapped) and container plants can be successful, though hot temperatures, dry conditions, and non-dormant trees makes good care especially important and survival less sure. Bare root trees should only be planted in spring while still dormant.
Q: Of those types of trees, which is best?
A: Landscape trees and shrubs can be obtained in four basic types: balled and burlapped (B&B), container/potted, bare-root, and tree-spaded. Each type has advantages and disadvantages and none is ideal for all situations. Bare-root will give the tree the most naturally formed root system and they are less expensive, but they are not commonly available from nurseries. B&B trees are good because they have been grown for several years in soil and are more likely than potted trees to have a well-distributed root ball. Potted or containerized trees are the worst, with it much more likely that the tree will develop root system problems like girdling roots and buried root collars. Spaded trees are good but may not be available.
Q: How large does the root ball need to be?
A: With all four types you need to have an adequate root system – a good rule-of-thumb is that the root system, root ball, or container diameter or spread should be 10 inches to 12 inches for every inch of stem caliper (diameter at ground-line just above any basal swell). Therefore, a 3-inch caliper tree should have a 30 inch to 36 inch wide root ball as a minimum. Root ball depth is not as critical as width but should be larger for larger trees.
May 9, 2017
Q: We have cut down a maple, sycamore and ash tree that were growing in our yard and roots had spread on the surface causing the grass to die. How far down do we need to remove the roots so grass can grow?
A: The roots did not kill the grass. Shade from the tree did, along with competition from the tree for water and space to grow. Just remove the stump and roots down a few inches so you can put some soil down so the grass roots have soil to grow in.
April 18, 2017
Q: Hi, we live in Grantsville out past Tooele and we were wondering if it is too early to prune our Peach and apple trees. Could you help us on this?
A: It is definitely not too early to prune apples, and probably not too early for peach. Because pruning can result in a slight loss of cold hardiness sin the remaining branches, it is generally recommended that you don’t prune until the risk of severe cold has passed.
Many commercial growers are now pruning peaches, but also watching the weather. If there is extreme cold temperatures (single digits) in the forecast, then stop pruning until the cold weather has passed.
April 07, 2017
Q: Is the blue spruce on my property is at risk for bark beetle infestation? I go every year to chop down beetle killed trees in the Uintas, (pond pine, white fir), I bring it home, and use it for firewood. I have a blue spruce that I'm concerned may become infected.
A: You are only putting your spruce at risk if you bring spruce logs down to your property; beetles are species specific. Bringing ponderosa and white fir will not threaten the spruce. Hope this helps.
March 07, 2017
Q: Hi, we live in Grantsville out past Tooele and we were wondering if it is too early to prune our Peach and apple trees. Could you help us on this?
A: It is not too early to prune apples, and probably not too early for peach. Because pruning can result in a slight loss of cold hardiness in the remaining branches, it is generally recommended that you don’t prune until the risk of severe cold has passed. Many commercial growers are now pruning peaches, but also watching the weather. If there are extreme cold temperatures (single digits) in the forecast, then stop pruning until the cold weather has passed.
March 07, 2017
Q: I recently purchased a lot and built a house in Delta, UT. The soil here is very alkaline and I am trying to come up with some sort of plan as to how I will be able to get some trees to grow. I've heard that green ash can do well in this environment but I'm having some difficulty in finding any good info on what and how to plant. Please, if you have any suggestions or could even point me towards some literature on this topic I would be very grateful.
Thank you for your time
A: Green Ash does well in high pH soils in Utah. Planting really is nothing out of the normal, make sure that the hole you plant in is 2 to 3 times larger than the root ball and mix the excavated soil with a good compost to enhance the organic matter content of the repacked soil. This will improve the soil structure over time around the roots and the tree should do well. If planted in with a lawn, the regular fertilization of the lawn will provide sufficient nutrition to the tree as well. Be sure not to cover the crown area of the tree (the point at which the shoot and root join). This can cause rotting of the bark above the crown and the tree will be susceptible to fungal and bacterial disease.
If you are interested in other trees that can tolerate alkaline conditions and want to preview other features such as fall color, spring bloom, decorative bark and other desirable features you can consult the on-line Utah Tree Browser put together by our Extension Urban Forestry group. The browser can be found at:
One piece of education and advice. Utah soils are alkaline because of the large quantity of Calcium Carbonate (or lime) that they contain naturally. Utah soils can contain anywhere from 15 to 40+ % lime by weight. This lime is a very reactive buffer against pH change and consumes large quantities of acid as it dissolves. One would have to dissolve ALL the lime in the soil before pH can be lowered. In practical terms, this is impossible given the scale of the requirement for acid to accomplish this. One percent by weight of an acre 12 inches deep is 40,000 lbs or 20 tons. Utah soils therefore contain 15-40 times 20 tons of lime in the top foot of an acre of land. So, you can see the problem of scale we are up against. Even our irrigation water contains large quantities of dissolved lime (hence the nice hard water deposits on our faucets and drinking glasses and our windows after the sprinkler wets them!). So, there is just too much pH buffer in our systems to ever try to adjust pH. Better to select plants that are tolerant of alkaline conditions.
Hope that helps.
Professor and Extension Soils Specialist
Utah State University
Q: I’m a hiker (and hike leader) and recently came across a pine tree that I can’t
identify. It is located in Sterling Forest State Park, Tuxedo NY, and is one of its
kind that I have found. It has a dark green, almost blue, glossy, thick, 5-6 inch needle, with three needles
to a bundle (fascicle). I know its not a white pine (there are lots of them and they
have 5 needles to a bundle) and my research seems to believe its a Pinus Ponderosa
or Pinus Jeffery (pine), neither of which are native to this area and are predominately
in CA and the far west region of the USA.
Could it be someone planted it? If it helps, the tree is near Sterling Lake, once a mining area for magnetite.
This is driving me crazy!! Can you help?
A: Actually, that is a better description of Austrian pine (Pinus nigra). They have needles in 3s (ponderosa is in 2s and 3s), and 5-6" long needles (ponderosa
needles are longer). If you have cones, ponderosa has sharp prickles on the tip of
each scale. Austrian has a bump, but no prickle. And mature buds on an Austrian pine
are white, while they are reddish-brown on ponderosa.
October 10, 2016
Q: I have an Elm tree that is dripping a clear liquid on my lawn. The areas of the lawn affected by the liquid have been killed. Do you have any suggestions on how to remedy this?
A: Gene, the only thing that might do this is bacterial slime flux that oozes out of wounds in elms, willows, and some other trees. Normally the waste from this disease runs down the trunk from old pruning wounds and eventually kills grass. I haven't seen this in the form of dripping material, but I suppose it could happen.
Regardless, there is nothing you can do about the disease, and it doesn't harm the tree much. If you mulch under the tree there won't be any grass to kill.
October 02, 2016
Q: We live in Blanding, Utah and planted 52 new 4-6 ft. trees in March 2016. We have been watering them 3 times a week (about 10 gallons per watering). Now that it has cooled off and turning fall, how often do they need watered?
A: Roots will grow as long as the soil they are in is moist and while the soil temperature
is above 40 degrees F. And it is good for roots to keep growing because it will speed
the trees' recovery from transplant shock. But once it cools off enough then little
water will be transpired from vegetation and it won't take much to keep the soil moist.
So as long as it stays cool you can back off to maybe once every couple of weeks,
or don't water at all if you get significant precipitation. A good way to tell how
deep you are watering if the soil is not too rocky is to use a probe like a long screwdriver
or a steel rod welded to a handle to form a tee. It will penetrate moist soil and
will stop when it reaches dry soil. You would like to water enough that the soil is
moist down to at least a foot.
September 12, 2016
Q: I have an ornamental weeping cherry, and I believe it was grafted. I would like to prune it so it can retain it's weeping form. What do you suggest?
A: With grafted plants it is important that you know what is the rootstock and what is the top. Often plants are grafted just above ground with one plant that has it's top completely removed, the rootstock, and one or more plants that have no roots but are desired for traits that their tops have. In the case of almost any trees that have a weeping top and an upright stem, you actually have 3 or more plants -- the rootstock, the upright stem (which may be a part of the rootstock), and the weeping part. And on some ornamental cherries there may be several top branches attached to the top of the upright stem.
Any of the parts of such a plant may form buds and those buds can grow new top material, but if you want to retain the grafted form as it was meant to be, you have to prune off such shoots. In some cases, like with twisted forms, the twisted top may actually grow slower, and if a straight shoots come off of the rootstock, they may eventually shade out the twisted parts.
I hope that this helps. Mike Kuhns, Professor, Extension Forestry Specialist