Keep Douglas Firs out of city gardens

Keep Douglas Firs out of city gardens

Keep Douglas Firs out of city gardens

Like animals, some trees just don’t domesticate well. They belong in the wild. Our venerable and beloved Pacific Northwest Douglas Fir (Pseudotsuga menziesii) is a prime example. Yet, scan the horizon of Madison Park and you’ll see them poking up here and there.

Oddly, all are about the same height and age: all are about 100 feet, likely 75 or 80 years old; far too young to be leftover old growth, and too old to have been planted after the sophistication level of our gardening public kicked in during the mid-20th century.

OK, why are these indigenous behemoths here?

I have a theory. 

When I bought my house in The Park in 1974, there was one on my tiny lot, and two more looming up along the driveway, adjoining my property to the south. Today, these would be like the others I see in size. At that time, I asked the daughter of the family selling the house about these trees.

“Oh, that’s my brother.” She rolled her eyes. “There was this Boy Scout troop in Madison Park back in the ’40s. They gave out these seedlings, and all the boys came home and planted them in their yards.”

Ah ha! Now, as I look across the Madison Park skyline, I see the ghosts of early Eagle Scouts hovering in these trees.

I had the three in my little garden taken down. Not only were they shading out everything else I wanted to plant, they also were insufferably greedy water suckers. As I recall, it was Art Kruckeberg, the pioneering professor of botany at the University of Washington, who said a Douglas Fir can pull 300 gallons of water out of the soil on a hot day. No wonder my soil was dry! Then, too, I was worried that one of these giants would come down on my house (or worse a neighbor’s) in a wind storm.

So, there’s the case for never planting a Douglas Fir in your city garden. Now, what do you do if you have one?

Option 1: Call in a tree service and have it removed.

Option 2: Live with the tree. Study up on gardening in the dry shade. Irrigate when you must. Add copious layers of mulch to the ground under the tree and fill the area with drought-tolerant natives like Sword Fern (Polysticum munitum), the Giant Chain Fern (Woodwardia fimbriata) — with fronds that can reach 9 feet — and our ground covers, Mahonia nervosa and M. reopens. There are plenty more choices. Do your homework. Research is fun.

Option 3: If you choose to keep the tree and fear that a big wind might bring it down, you can ameliorate its mass by using the Betty Miller method.

Elisabeth C. Miller was the legendary horticulturist and genius gardener who, among multiple other accomplishments, founded and funded the Miller Horticultural Library at the UW Center for Urban Horticulture and the Miller Botanical Garden (of which I am a proud board member.) Betty left us in 1994, and I am one of the few people alive who knew her well.

Betty loved her towering Douglas Firs, and she had an amazing system to manage them. She’d send climbers into the trees who would spiral up, taking off every third limb as they went around. The limbs would plunge to the ground. She’d snip off the supple ends to use as winter protection for tender plants; larger pieces would be cut into lengths for the fire pit. The benefit to the trees was twofold. First, it slowed the growth of the tree. Secondly, it allowed wind to move through the tree, lessening the possibility that it would be taken down in a storm.

The bottom line here is simple: Never plant a Douglas Fir in your city garden. But if you have one, consider the three options. If you choose to leave it in place, you’ll have my gratitude. I love looking over The Park and seeing them punctuate the view above the rooftops. These trees, which can reach more than 250 feet in height in our forests, are among the most majestic conifers on Earth. Beautiful year round, fragrant, dramatic in the wind in movement and sound, they block the harshest light and catch the softest rays. As the dawn breaks or the sun sets and the light pours horizontally through the branches, take a good look. You’re quite likely to spot the ghost of Madison Park Eagle Scouts roosting in the limbs.