Browning of Evergreen Needles

What causes the needles to brown in the winter?

Usually this is a result of damage caused by the winter. The reflection of the sun off the snow will cause evergreen needles to turn brown. When they run short of moisture in late winter - early spring, the needles will also turn brown. This browning will continues into late spring even after the frost has gone out of the ground.

What can be done in the spring?

My first recommendation would be to not over react and do alot of watering if the plants don't need it. Only water if they seem dry. For pine and spruce I would wait to see what happens when the new growth comes out. If the new growth comes out green & healthy, you may be able to prune off some of the brown. For the arborvitae, junipers and yews cut off twigs and stems which are totally brown and starting to shrivel. Don't cut off anything which is pliable or green, new growth may emerge from that tissue.

Can anything be done to green up evergreens which are yellowed or brown?

Applying a foliar spray of Miracid seems to help green up evergreens which are yellow or an off green in color. Since it's a foliar spray you may want to repeat the application several times at two week intervals. Nothing can be done to make brown dead needles turn green.

What can be done to prevent the needles from browning again next winter?

Water your evergreens very well just before the ground freezes in the fall. This allows the roots to take up the maximum amount of water and hopefully provide enough moisture to last through the winter.

Hackberry Leaf Drop

Why do the leaves turn yellow and drop off?

No one is sure but I've found out that hackberries are very responsive to hot dry conditions. During the last few years they have shed leaves about the same time each year.

Will all the leaves turn yellow and fall off?

In past years the trees have shed some of their leaves and held the rest of them until normal leaf drop in the fall. It is almost as if the trees are shedding the leaves which they can't support.

Is there anything which can be done for these trees?

If we don't get rain within the next week or so, watering certainly wouldn't hurt. Fertilizing the trees next spring would also be a good idea.

Are the small nipple like growths on the leaves a problem?

No, the growths on the leaves are called nipple galls and are not a problem for the trees. They are caused by an insect feeding on the leaves just as they emerge in the spring.

Rabbit Damage

Can anything be done for trees and shrubs which have been damaged by rabbits?

At this stage of the game it's pretty difficult to repair damage done by the rabbits.

Will trees and shrubs die from the rabbit damage?

When the bark in eaten off the trunk or a branch all parts of the plant beyond the eating will most likely die. If the bark is only eaten off one side of the limb the bark will regrow over a number of years.

What can individuals do in future years to prevent winter rabbit damage?

We recommend wrapping the trunks and branches of trees before going into winter. Putting chicken wire around vulnerable shrubs will prevent rabbits from eating on them until the snow gets very deep.

Wind Damage

Ice storms and high winds severely damaged many trees. The ice adds considerable weigh to tree limbs and the winds twist, break, split or even topple trees. Both evergreen and deciduous trees can be damaged.

If the main trunk has been broken or the tree has fallen with more than half the roots exposed, the best plan of action is to remove the tree. Broken branches should be pruned off. When removing a branch cut back to the nearest side branch or back to the main trunk. Never leave a ragged stub or cut right flush up to the trunk. Instead, cut beyond the branch collar (just beyond the thickened junction of the trunk and branch). The smaller the wound the quicker it will heal. Do not cover the wound with a pruning paint or wound dressing. Research has shown that these substances can cause as much harm as they do good.

Small trees which are leaning or completely blown over can be reset.

Contact an N.D.S.U. University Forestry Specialist and have them evaluate your tree before you attempt to repair any tree.

In general it is best to reset only smaller trees, since larger trees will always be weak and may fall again, perhaps damaging property. Leaning trees should be repaired as soon as possible. Once trees have been straightened up they will require anchoring and bracing with padded guy wires for up to two years. After resetting, water the tree well and keep it watered during dry periods.

To learn more about proper pruning techniques, get a copy of the NDSU Extension Bulletin "Pruning Trees and Shrubs" from your local Extension office or online at http://www.ext.nodak.edu/extpubs/plantsci/trees/h1036w.htm.

(701) 231-8143 or go to the ISA's Web page at http://www.treesaregood.com/.

What can be done for trees and shrubs damaged by wind?

If the branches have been badly damaged, remove them. If a branch has actually broken or snapped off from wind our best bet is to remove it making a clean cut. A clean neat cut will heal faster with less change of being infected by insects or diseases.

Should the pruning wounds be sealed after removing these damaged limbs?

Normally we don't recommend using a pruning paint or wound dressing on pruning wounds. Research has shown that these substances can cause as much harm as they do good. The only exception may be plants which could get infected with fire blight.

What should be done with trees which have been tipped or blown over by the wind?

Generally small trees can successfully be pulled back up, staked, and will recover to be a worth while tree in the landscape. Large trees can be set back up and staked but will always tend to be weak and may blow over in future storms.

Woodpecker/ Sapsucker Damage

What type of damage do sapsuckers inflict on trees?

Sapsuckers make small holes in the main trunk or large branches of trees. These holes are usually in a row or pattern which is characteristic of sapsuckers.

Just what exactly is a sapsucker?

Sapsuckers are a type of woodpecker which makes holes in a tree and uses its tongue to remove sap. They usually have a few favorite trees and may leave nearby trees completely untouched.

What can be done to prevent the sapsuckers from damaging a tree?

Usually with them out of sight means out of mind. Wrapping burlap loosely around the damaged area and tying it in place is usually enough to cause the sapsuckers to look for other targets. If it blows in the wind that will also scare them.

Can they kill a tree?

Yes, if they continue working on a particular tree it may eventually die. The sap leaks out the holes and doesn't get up to the leaves and branches. Pruning paint doesn't help seal the holes because the sap pressure is from inside.

Yellowing of Plant Leaves

What causes plant leaves to turn yellow?

Usually the yellowing of plant leaves is caused by the inability of the plant to take up enough iron from the soil to keep the leaves green. This condition is worse when we have a lot of rain or water heavy.

What is this yellowing called and what symptoms should we look for on the plants?

We call this condition iron chlorosis. A sure fire method of distinguishing this condition from other problems is to examine the affected leaves closely. With iron chlorosis the leaves will be yellow but the veins in the leaves will be a greener color.

What can be done to treat iron chlorosis?

Iron supplements are available in both the liquid and powdered form. The liquid form when mixed with water works good on low growing plants and shrubs but has short term results. The powder which needs to be gotten down to the roots is slower acting but has longer term results.

This page was last updated August 2002

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