September, the Harvest Moon month, is a love-hate month for gardeners. This month brings dramatic changes to our landscapes. Although this is an annual occurrence, we somehow are always emotionally unprepared. Hot sunny days early in the month lull us into a false sense of complacency, believing that summer is everlasting.
Yet one heavy frost abruptly ends the seasonal life of annuals, and snow (yes, it does snow in September) breaks branches and creates landscape havoc.
Many gardeners welcome September’s slower pace and shorter days after toiling in summer’s heat. Now is the time to savor the late season harvest and begin consigning healthy, spent foliage to compost piles.
Those who consider September to be a month of death must realize that nature is on a continuum, always re-energizing itself. If things were permanent, we’d have eternal landscapes of iris and peonies. Many of the plants we love receive that love because their blooming season is so short but their roots are busy regenerating themselves during their non-blooming season.
September changes the focus of our gardening activities. First of all, photograph your garden and landscape, both for memories and for a springtime guide when you plant again.
Then, discontinue evening watering to discourage mildew and slugs, and then reduce all watering, especially around trees. They need to harden off to withstand early frosts and snowstorms. It’s also time to scrutinize trees and shrubs that might be fragile or near power lines in case of early snow because our most dangerous snow storms arrive in early fall and late spring.
Q: We like bachelor buttons and mostly keep them confined to one area. They are unsightly when they go to seed, but the blank area after they’ve been cut down is even worse, especially to our neighbors who have “golf course” lawns. Is there anything we can plant to freshen up the now-bare spots?
A: Wildflowers and self-seeding annuals are fine in nature where plants freely continue their life cycles. They become a problem in urban landscapes where neatness is expected.
For now, I suggest you buy some inexpensive mums. They’ll give instant color and may even survive the winter. Then, in the spring, intersperse the bachelor buttons with alternate blooming flowers such as gaillardia, coreopsis, monarda, rudbeckia, phlox or daisies. You get the picture.
Don’t plant too heavy because you must leave space for the bachelor buttons to re-seed and develop sturdy systems.
Q: Last fall while vacationing in the Upper Midwest we were captivated by the colorful, bittersweet vines we saw. We brought some seeds here and planted them, but with no results. The seeds didn’t even germinate. Bittersweet is supposed to be OK in our climate zone, so how do we start it here?
A: First of all, you don’t want bittersweet in an urban landscape. It is as aggressive as bindweed. Secondly, zone designations primarily consider temperature ranges and don’t recognize the many variables, such as soil composition, rainfall, wind and insect environments. These variables even exist within our city.
Denver’s clay soil, plus our intense high-altitude heat, irregular rainfall, sudden temperature shifts, wind bursts and air pollution all challenge our plants. Ours is as very different environment from the acidic, woodsy environments bittersweet vines find in the Upper Midwest.
Q: Our landscape always looks so lackluster at this time of the year. It looks even worse this year because so much foliage was hail damaged. What can we do for color now?
A: Buy lots of colorful blowsy mums. They’re inexpensive and make dramatic statements when massed. Also, buy pansies. These cheerful little bloomers love the cooler temperatures and will last through frosts. Mass one or two colors to fill blank spots.
These are immediate solutions, but the real solution comes with serious planning in the spring. We are often so dazzled by the color parade nature offers in the spring that we don’t plan ahead. The solution is to note attractive landscapes and consider some of those plantings. Since all plants have peak seasons, you must include such late-bloomers as agastache, penstemon, gaillardia, rudbeckia and lots of striking lavender and ornamental grasses. Such annuals as cosmos and zinnias also bloom until late frost. Don’t be afraid to experiment.
Q: How do I prune my overgrown raspberry bush?
A: Ruthlessly remove all old wood. Raspberries produce fruit on two-year-old canes, so the older wood just absorbs space, creating an impenetrable thicket.
Enjoy September, when
“The morns are meeker than they were – / The nuts are getting brown / The rose is out of town.” —Emily Dickinson
Joan Hinkemeyer is a long-time gardener from a family of green-thumbers. She was an estate gardener in Beverly Hills, California, and had her own landscape consulting business for over 20 years.
