Q: This garden is full of unusual plants. Which of these should be grown in more home gardens?
A: The red horsechestnuts (Aesculus x carnea 'Briotii') grow well in Northwest gardens, as do all kinds of Ceanothus ― from the 10-foot-wide C. 'Concha' to wonderful groundcovers like gloriosus, griseus horizontalis, and prostratus. Coast silktassel (Garrya elliptica) is an underused native that really stands out in winter. Among roses, I suggest planting 'Bonica', a free-flowering variety that has wonderful red-orange hips in fall and winter.
When you're replacing one of the garden's choice trees or shrubs, do you shop for specimen-size plants or smaller ones?
I'm one to buy small plants: 1-gallon size mostly, never bigger than 5-gallon. Smaller plants seem to grow faster and adapt to the garden better than bigger plants.
Where do you shop for unusual plants?
Forestfarm in Oregon is one place (541/846-7269). We also keep replacement plants in an on-site greenhouse and nursery, and sometimes extra palm trees are sold at the visitor center (look for windmill palms this month).
The garden contains plants from 104 families, 299 genera, and 573 species. How do you keep track of it all?
For container plants, we bury one tag in the bottom of the pot and attach an identical tag to the actual plant. For garden plants, we bury one tag on the north side of the rootball when we plant and put a second tag on a branch. We also number each planting bed and cross-reference the plants with bed numbers in our database. We used to keep our records on file cards, but the computer is better: When we lose a tag, we just print another one.
Do you use chemical sprays for pest control?
A little. We started an IPM (integrated pest management) program in 1989, and as we've reduced spraying, we've seen increased bird populations, and the butterflies are back. Now, when the staff sprays at all, it's just for spot control of weeds and for major problems like last year's tent caterpillar invasion. When we have to spray, we do it in the still air of early morning, when insects aren't out. For home gardeners, I think evening's the best, since beneficial insects like bees aren't active then.
How do you deal with weeds?
We mulch every bed with 2 inches of wood chips, which we get free from tree trimmers. We also spot-spray with Roundup because it's biodegradable: Once it comes in contact with organic matter, it starts breaking down rapidly.
Do you fertilize your trees and shrubs?
Yes. In January, after we've renewed the wood chips on the garden beds, we feed. One 7-pound coffee can full of 5-10-10 fertilizer covers about 200 square feet.
What's your watering program?
For decades we watered every week for an hour. But since the soil here is clay, most of the water we applied would run off, so the tree roots never went very deep. After we lost a great tree in a storm ― it was a Nothofagus dombeyi ― I started applying less water more often. That eliminated runoff and kept the soil moist deeper down. We haven't lost a tree since.