Brown needles, broadleaf weeds

By John Fulton

[September 22, 2010]  Brown needles happen on pine trees and other evergreens all the time. Of course, some of the times are more striking than others.

Is this a bad thing? It all depends.

To begin with, evergreens keep only one to four years of green growth toward the tips of the branches. The number of years is dependent on weather conditions, the health of the tree and the species. Needles toward the trunk of the tree turn brown each year and drop off.

If weather conditions are just right, the needles all turn brown at once. If there aren't any heavy rains or winds to help knock needles off gradually, the brown needles are quite showy. They will drop off and the appearance of the tree will return to normal. The only exception is the green needles are now farther away from the trunk.

Every evergreen has a "dead zone" for these reasons. A dead zone has no green needles or buds in it. You end up with a dead tree prune if you prune into the dead zone. This can also make for unsightly trees when the branches become very long and begin to droop. This exposes the dead zone and makes the trees appear to be sparse.

Stressful years make the brown needle phenomenon more pronounced. I would classify this year as highly stressful, with the combination of heavy rains and heat. This type of weather is worse on evergreens than most plants, because most evergreens planted over the last 50 years really aren't very well suited for central Illinois.

White pines are really a northern understory tree. That means they are better suited for Wisconsin and north and in a mixed timber with other trees that shade them. Spruces and firs are mostly western, high-altitude trees. Red pines are native to the Northeast and to northern Illinois, but they have some disease problems. Austrian pines have many disease problems and don't usually see 40 years old. The white (concolor) fir is another western species but has held up about as well as any evergreen in our area.

As for what to do, just take good care of the trees. Fertilize the lawn area around the trees at the lawn rate to supply a pound each of nitrogen, phosphorus and potassium per 1,000 square feet in the fall and the spring. The trees will get the fertilizer they need before the grass can get it. The drying winds of winter may also take their toll. Use a wind block, or treat with an anti-dessicant such Wilt Pruf, to keep needles from drying in the winter.

Broadleaf weed control

Fall is a great time to try to control problem perennial weeds in the lawn. The weeds are in the process of storing energy in the roots and crowns so they can come out again next year. This translocation of food also provides a great way to move pesticides in the plants.

Problem perennial weeds would include things like ground ivy, violets, speedwell and others. Of course, a treatment will also get dandelions and plantain.

For most problem weeds, a combination of 2,4-D, MCPP and dicamba will do the trick. There are many pre-mixed herbicides with these ingredients. Many are adding triclopyr to the mixture as well, and mainly for violet control.

Try to pick a day when winds are slight and when temperatures aren't predicted to be above 85 degrees for a while. Normally the late September time doesn't present the temperature problem, but this year seems to be an exception. The dicamba can vapor drift after application. Many gardens are about done, but flowers, shrubs and trees are also translocating food. You need to be cautious whenever applying chemicals. Read the label and follow all recommendations.

[By JOHN FULTON, University of Illinois Extension, Logan County]