Margaret Lauterbach

Spring full of pollen reminds us of split between male-female trees

The pollen might not be so bad that you can do this on your car window, but it’s definitely a factor in the Boise area this spring.
The pollen might not be so bad that you can do this on your car window, but it’s definitely a factor in the Boise area this spring. AP file/CT Sinus Center

Maybe it’s my imagination, but it seems as though every spring has had different weather in the Treasure Valley, and I’ve lived here for nearly 50 years. This year is not as windy as many previous springs, but the pollen excess has everyone sneezing, blowing and gasping.

Pollen must be reaching its targets, too, for seeds are everywhere. I’ve been tempted to use a vacuum to get elm seeds out of my garden so I don’t have to dig out trees. Some wonder whether their tree is dying, because dying trees do produce a lot of seeds in an effort to perpetuate their species. Another explanation could be that it’s a “mast year,” when seeds are extra prolific, although usually the term just refers to seeds such as acorns that are used for animal food.

Landscape architects and homeowners tend to prefer male trees when faced with a choice, because female trees produce “fruit” (fruit, cones, nuts, large seeds, etc.) that are considered trashy. Male trees produce pollen in great clouds, in an effort to reach female trees, and in the process causing armies of sneezers, coughers and purchasers of antihistamines. In nature, the ratio of male and female trees is about 50-50, but in urban areas male trees constitute over 90 percent of the tree population. That’s also the reason some types of “hay fever” are worse in cities than in countryside.

Male trees? What are those? They may be ash, cedar, pine, poplar, willow, juniper, cottonwood, maple, box elder or any of a thousand other species of gender-specific trees (dioecious). In many species, it’s difficult to tell the gender when the tree is young, and like some old poultry hens, they may change their gender after maturity. For several years the street trees in the 8th Street marketplace area were those ancient relics, Gingkos. A petrified forest of these trees was found years ago in Washington state, and the estimate is that the species is over 270 million years old. Each Gingko leaf is a fan shape, unlike most other tree leaves, similar only to those of the maidenhair fern. Gingko leaves on 8th Street turned a warm gold in autumn. Those 8th Street trees came into fruiting age, though, and nobody was using the fruit, so it fell onto sidewalks, rotted and stank.

The city was pressured to remove those trees, so it replaced them with less offensive and interesting trees.

The ash aphid

A different breed of insect is making its presence known this spring in great numbers. The woolly ash aphid is freaking out some of us, and causing concern to many. They’re aphids with cotton boll-like coats, designed to ward off predators. Fortunately they don’t work perfectly. Those “cloaks” are waxy filaments formed by the aphids themselves, and it does protect them from sprays and to some extent beneficial insects’ attacks.

Like other aphids, they reproduce without partners (that is, parthogenetically), and begin reproducing other aphids very quickly. They’re more numerous some years than others, but the woolly ash aphids can do severe damage to young ash and fir trees, especially the roots of those trees. Mature trees can take it, even though their leaves may be distorted and not aesthetically pleasing the entire season.

Since they’ve shielded themselves from sprays, these aphids could be controlled with systemic insecticide. Some systemics are used by drenching the soil, and others are sprayed to soak into leaves. But the first is damaging to the microscopic creatures in the soil, and the second might be poisoning the beneficial insects who feed on the bad guys. Those toxic drenches are costly, too. It’s better to do nothing, if your affected trees are mature. If the honey dew excreted by the aphids becomes sooty and its drops a nuisance, that can be washed off leaves with a strong jet of water.

Beneficial insects always wait for the setup of a feast before they begin to attack, so their appearance lags behind the gardener’s alarm at large numbers of marauders. As long as you let things be, the beneficial insects will come to your defense. The best idea is to always evaluate whether destructive insects are doing minimal or a lot of damage. If damage is more than you can tolerate, then use the least toxic control available to start with. I always prefer beneficial insect control, because insects can develop resistance to chemicals, but not to predators.

Helping figs

Revisiting Lee Reich’s new “The EverCurious Gardener,” I found that he reports putting a drop of oil (usually olive oil) on the eye of a nearly ripe fig while it’s still on the tree or shrub will hasten ripening. I have had only one fig ripen over several years’ time, so I’m going to try that.

Send garden questions to melauter@earthlink.net or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.

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