Growing Concerns 37: Pine scale, rex begonia

Pine scale

In the fall I noticed my mugo pines had a whitish gray substance on them. Before I could find out what it was the snows came. Since the snow melted I notice they're still gray. What can I do to get them normal looking again? - C.S. -

You're almost certainly looking at an infestation of pine needle scale, an insect. The whitish gray stuff is adult scale bodies attached to the needles. Though it's a common problem and ugly to look at, it's not usually deadly.

To remedy this, watch for snowmound spirea bushes* (Spirea vanhouttei) to bloom, about the third week of May. That's when scale eggs hatch and minuscule young scale (crawlers) come out from under the dead adult's shell that's protected them all winter.

Once in the open, crawlers can be killed. Use dormant oil or fine horticultural oil (available at local garden centers), petroleum products so finely atomized they can be mixed with water in a sprayer. Tiny droplets of oil clog breathing pores in the insects' shells, smothering the pests.

One well timed spray can go a long way. A lot of crawlers die right away, plus oil residue stays on the needles for a few days, killing more scales as they hatch.


In a bad infestation (your case qualifies), it's a good idea to treat again when the second generation hatches. That's in July when snowball hydrangea flowers* (Hydrangea arborescens) are turning from white to green.

Read the label on oil carefully. Use as directed, in the recommended amounts - as with any pesticide, poor timing or using too much does more harm than good.

*To use plant development stages to predict the occurrence of pests, we use “Coincide” by Donald Orton. It represents a twenty year study of fascinating seasonal parallels between plant and insect development. For price and ordering information, write to Plantsmen's Publications, P.O. Box 1 , Flossmoor, IL, 60422.

Rex begonia just resting

We bought a Cleopatra begonia last summer. In front of a large east window, it grew well and developed a myriad of babies. In the fall, the babies started dying and larger leaves dried up from the tip. It was a showpiece and we hate to lose it. Do you have any suggestions? - B.T. -

This is a Begonia rex hybrid, grown more for pretty leaf than flower. Low light or drought can make begonia leaves fall, but it sounds like your plant's decline was not a response to poor growing conditions. We hope you kept the remains, because it was probably just entering a normal dormant phase and can be expected to revive.

While in active growth (March to November) these plants like strong half day sun, high humidity, and soil that gets bit dry before its next thorough watering. Then one fall they get old enough to take a rest; they begin to collapse and lose leaves, no matter how good your care might be. Your large plant was probably just old enough to take a break, though cool conditions may also have triggered dormancy.

Put the pot in a cool place and water it only enough to keep it from going bone dry. Return it to warmth and light in March and it will resume growth.

Trees and shrubs for wet spot

Along our property line there is always standing water. We'd like to plant for privacy. What type of hardy trees or shrubs would do in this situation? - K.W. -

Try not to confuse the term hardy - which indicates how much cold the plant can tolerate - with the ability to live in other kinds of adversity. The hardiest plants in the world can survive Siberian winters but can't live where it's too dry, too wet, or too acid.

Try some of these shrubs, all native to wet areas. In sun: pussy willow (Salix discolor), elderberry (Sambucus canadensis), or buttonbush (Cephalanthus occidentalis). For shadier areas (at least four hours of sun each day): silky dogwood (Cornus amomum) or Michigan holly (Ilex verticillata). We like these not just because they'll grow but for pussy willow catkins, elderberry flowers and fruits, fragrant buttonbush flowers, silky dogwood's fall color, and winter fruits on the holly.

All of these wetland trees need sun: red maple, (Acer rubrum - also known as swamp maple), sycamore (Platanus occidentalis) or Tamarack (Larix laricina).

Start with small plants. We've noticed that once a woody wetland species invests a few years in developing a deep root system in well drained nursery soil, it struggles pitifully to switch to its native environment where shallow roots are needed. Younger plants adapt more quickly.

Experienced gardeners may shudder over this list. Wetland trees and shrubs tend to be fast growing, And the shrubs tend to become thickets. Most have soft wood that breaks and makes a mess. So if you want neatness as well as privacy, plan to prune out deadwood regularly - not always a pleasant job while standing in the muck.