Wondering why your allergies are kicking up? Do you have nasal and sinus distress? Stop wondering: we live in an area of pollen-laden trees.

I had no idea how strong a correlation there is with local tree varieties and the distress many face until a reader of our columns from Ontario became an email friend. He has just published a book, "Veterans Gardening Guide," that illuminates and promotes allergy-friendly planting.

Peter Prakke, the author, was a child during World War II in eastern Holland. He became a horticulturist who worked worldwide, even creating an allergy-friendly park to honor veterans as well as allergy-friendly schoolyards. His work led to his book for people with allergies, asthma, and COPD. It features "OPALS."

Prakke explains that OPALS, the Ogren Plant Allergy Scale, developed by Thomas Ogren, is based on two criteria: 1. What do well-known plants that create allergies have in common?; and 2. What do plants that are well-known to not cause allergies have in common?

More than 130 criteria were used to create OPALS rankings that range from 1 to 10, with 1-3 being low and 9-10 extremely high in allergy-causing problems.

Birch, alder, and willow trees are among the highest scoring species, in the 9-10 range. The iconic birch, so admired by people in northern Minnesota, produces copious amounts of pollen

The early blooming pussy willows that flower when there is snow on the ground, start the long willow season of sneezing and stuffy heads. Male trees and shrubs are most often the culprits.

Male trees are often recommended for urban landscapes and boulevards for one simple reason; they aren't messy. So necessary to pollinators, female trees produce fruit, seeds and seed pods that clutter up our vacuumed lawns. The problem for folks with respiratory issues is that male trees produce copious quantities of pollen grains that are "very small, light and buoyant; the most allergenic." Many of these trees are wind-pollinated, meaning that this pollen can travel long distances, although most pollen is sticky and travels only 50 feet. Cities choose trees for many reasons; disease resistance, hardiness, size, beauty, shape and size, their shade capacity, but I have never seen any reference about selection due to their propensity to affect respiratory health.

Other trees that have high OPALS scores include male red cedars, white cedars, sugar maples, silver maples, oaks-bur, red, and pin, male poplar, hornbeam, ironwood and ash-green and black. They all score in the 7-9 range of the scale. All are prevalent in our cities, landscapes, and woods and those are the reasons you may continue to be under distress this spring.

Dioecious species (separately sexed) offer the best opportunity for avoiding allergy producing trees. Males can be in the 9-10 range and females in the 1 range. Monoecious plants (those producing both male and female flowers on the same plant) include oaks and willows. Female flowering plants also produce more nectar for pollinators as well as fruit and seeds for birds, added benefits from choosing females.

Thanks to Mr. Prakke, we now have a resource to aid us in making choices that can affect our health and our community's health. Hopefully, nursery folks, landscape architects, city planners and foresters as well as those involved with respiratory health care, will become aware of it and act on it.

Click on "Yard and Garden at the University of Minnesota Extension website-www.extension.umn.edu-for gardening information. Local Master Gardeners will respond to your questions via voicemail. Call (218) 444-7916, leaving your name, number and question. Beltrami County Master Gardeners are also on Facebook.