Urban landscaper: beware of root girdling!

Root girdling on a young tree

“Girdling roots” are roots that grow around other roots or the trunk of the tree, eventually restricting their growth and choking off any nutrients they carry to the rest of the tree. The girdling can be on one side of the trunk, or in more sever cases, will encircle the entire trunk, causing the death of the tree. It is normally found on trees that are have been planted for several years, which gives the girdling roots time to enlarge and restrict the nutrient flow to the rest of the tree.


It is becoming a problem especially in urban locations, where trees are commonly planted in undersized holes in sidewalks along store fronts.

Research has shown that girdling almost always starts when the tree is young, even before it reaches the planting site. It turns out that a large percentage of the trees that experience root girdling were grown in containers to start. Because they are in a container, the roots grow in a circular fashion, and once planted, they continue to grow that way, eventually growing back on themselves or around the trunk.

Another cause of root girdling is planting trees too deep. Make sure you plant them at the “root flare” where the roots start to flare out from the trunk. Also, make sure that the planting hole is plenty large, because if the hole is too small, especially in a tight clay soil, it may have the same effect as planting it in a container.

Pruning: the basics

This is an updated version of the plant care sheet that I give my customers, who often ask about how to best prune a variety of different plants. Feel free to copy it and keep it in a handy place!

Evergreens: Evergreens that grow continuously can be pruned or sheared anytime during the growing dwarfmugho.jpgseason (except late August, which can increase the risk of winter-burn). Plants in this category include: Junipers, Yews, Arborvitae, and Hemlock. If this is started early and done on a regular (2 times a year) basis, your plants will retain excellent form. Pine and Spruce normally put on a single flush of growth, then stop. If you are trying to maintain them at a specific size, (such as Mugo Pine), prune back 1/3 to 1/2 of the new growth (called candles) in early spring. Pruning of evergreen trees will be minimal, especially once they are established. Left photo: Dwarf Mugo Pine

Shrubs: Timing the pruning of flowering shrubs will depend on when they form their flower buds. Early-Spring flowering shrubs, (those that bloom on previous years wood, such as Azalea, Forsythia) shendsumhyd.jpgold be pruned immediately after flowering. This allows new flower buds to form for the following Spring. Mid-Spring-to-Summer flowering shrubs, (those that bloom on current year’s wood, such as Gold Flame Spirea, Hydrangea and Potentilla) should be pruned in early Spring and cut back 1/3 to 1/2 to keep them full. Shrubs not grown for their flowers can be pruned anytime, but an early Spring pruning before leaf-out allows the new growth to cover up the pruning cuts. Overgrown shrubs can be renewed by cutting 1/3 of the older branches to the ground (such as Red twig Dogwoods). Right photo: Endless Summer Hydrangea

Trees: Pruning can be done any time, but early spring is probably the best time. Look for crossing branches, diseased or dead wood, weak branch unions, suckers and water-sprouts,and overall aestheticcraprairiefire.jpg shape. EXCEPTIONS: Don’t prune Oaks (especially the Red oak genus) or Elms between early/mid April and July 1st. The risk of Oak Wilt and Dutch Elm disease is much greater at these times. Others to watch are Hawthorne, Mountain ash and apple trees, all three which can be susceptible to fire blight, especially if planted in a poorly drained soil. It would be a good idea to sterilize your pruning tool with a 10% chlorox solution between cuts.

Don’t worry if, when you prune your maple or birch, it starts bleeding (oozing sap). It may be unsightly, but it will not harm the tree.You can avoid this by waiting to prune until the leaves are full size. Don’t try to stop it with tree pruning paint. It won’t work!
Unless absolutely necessary, be careful not to top your tree. Topping will result in a flush of new growth and in the long run will be more unsightly than if you had done nothing.
Above photo: Prairie Fire Crab.

For more detailed info I recommend the following websites: The first is an excellent fact sheet put out by the University of Minnesota. The second resource is put out by the federal government that is a liitle more detailed with more pictures.

Winter burn on evergreens

Minnesota’s winters can be really tough on landscape plants. The combination of cold temperatures, winter sun, and drying winds can damage or even kill buds, bark, roots. Hungry mice and rabbits can nibble away at bark and branches, causing severe damage or even death. In addition, evergreens, can suffer from winter burn, the most susceptible being juniper, pine, hemlock, arborvitae, and yew. New plantings can get hit especially hard.

Evergreens are usually one of the earlier plants to show visible signs of winter injury in the spring, known as winter burn. This happens when the ground is frozen, and the winter sun and wind causes the leaves to lose moisture. Because the plant can’t replace the lost moisture from frozen soil, they literally dry out and turn brown. This normally occurs on the south or southwest side of the plant, or if it is in an exposed location, on the windward side. A very important contributing factor is lack of snow cover, especially when the soil freezes early before the needles get a chance to acclimate to the cold weather ahead, causing even more moisture loss. A late cold snap in the spring after the branches have leafed out can also cause browning.pp789-01[1].jpg

This doesn’t necessarily mean the death of the plant, however, so don’t get impatient and cut out the brown branches. In many cases, the branch itself will still be alive and will send out new shoots. (See photo at right) However if you can’t stand looking at the brown needles, try getting out your old kitchen broom and brush them off of the plant. Just be sure you don’t break any branches. Photo at right is from R. W. Stack, North Dakota State University. Click to enlarge.


The best way to prevent winter burn on your evergreens is to plant them in the right location. Avoid locations that are both exposed to the northwest winter wind and the winter sun . Also keep them away from your furnace or clothes dryer vent! Some evergreens are more tolerant of winter burn than others. Tauton yew and Techny arborvitae are two that can be safely exposed to the winter sun.

Also, make sure your evergreens don’t go in to the winter with the soil dry. The plants need moisture in the soil to replace the moisture loss from the leaves. Make sure you water them well watered, especiallyNewU418[1].jpg if they have gone through a dry spell in the late summer or fall. October and November (and sometimes December) is not too late, as long as the soil is not frozen and will take the water.
If you have already planted them the situation described, or that plant “just has” to to be in that location, then some winter protection may need to Be provided,in the way of protection from the wind or sun. The most common way is to use a sheet of burlap (available at most large garden centers) wrapped around the plant and held together by twine. Just make sure you don’t wrap it too tight, and leave it open at the top for air to get in and out.

Anti desiccants have also been used. They are mixed with water and sprayed on the plant, leaving a “waxy” coating to prevent moisture loss. However, recent research has shown the results to be generally disappointing.