In the Garden: Autumn is a great time to plant shrubs
Fall is here and some of you have already had a killing frost in your gardens, putting an early end to your growing season. No frost for me yet, but I’m taking advantage of the cooler temperatures to do some down and dirty digging in my perennial garden, getting rid of plants that have taken over, redoing the beds and replacing plants that have died.
Autumn is a great time to plant shrubs and one of my new additions is a Rose of Sharon (Hibiscus syriacus), a plant I have been wanting for years. It is a New England classic, seen growing around most old homes and farmsteads. I always admire them when driving around the back roads or walking in cities such as Manchester or Concord. It seems like there are a multitude of Rose of Sharon shrubs bearing flowers in many different colors growing everywhere.
Native to Asia, they were first introduced in England in the 16th century and made their way west with the colonists. They are in the same family (Malva) as hollyhocks and mallows. Rose of Sharon is noted for its late summer blooms. They come in single, double and semidouble forms in pink, lavender, purple, white, red and true blue – a rare color in the flower world. If you are in need of a shot of blue to contrast with all the autumn yellows and golds, look for the variety “Blue Bird,” which is a clear sky blue with a red throat.
A multistemmed shrub, Rose of Sharon is hardy to Zone 5 and can grow to be from 8 to 12 feet tall and from 6 to 10 feet wide. If planted 10 to 12 feet apart, a row of them makes an excellent hedge. If you prefer, with careful pruning, they can be trained to grow as a standard tree-shape by removing the extra stems.
To produce the most blossoms, they need full sun but will still bloom in light shade. They like moist, well-drained soil. Mine are planted in very sandy subsoil, so we added lots of compost to the planting hole. Usually I don’t amend the soil around a shrub or tree because it keeps the roots from venturing out into the surrounding area, making a weaker plant, but this spot needed it. They flower on new wood, so prune it in late winter or early spring.
They are late to leaf out in the spring, so don’t give it up for dead too soon. Fertilize in the spring and again in early summer but not after July. If you want to encourage really huge blossoms, pinch off the buds and leave only two to three per branch. Deep snow cover will protect the roots during winter, but to be on the safe side, you can mulch them heavily after the ground freezes. This plant is not attractive to deer – a good thing since last spring we had a dozen of them hanging out in our yard, eating everything. It is good for migrating butterflies, though, which we haven’t had enough of this fall.
Though we usually think of hibiscus as a tropical flower, there are other hardy hibiscus plants besides Rose of Sharon. Tom grew “Southern Belle” (Hibiscus moscheutos) from seeds a few years ago. It has taken three years, but they are finally blooming. One is a huge hot-pink bloom, 9 inches across, one is a single bloom in creamy white with a red throat, and the other one hasn’t opened yet, so it will be a surprise.
Though they look very tropical with their huge, satiny flowers, the plants are hardy to Zone 4. Unlike the Rose of Sharon, they die back to the ground each year but make an amazing amount of growth over the summer reaching from 3 to 4 feet tall. Every day I drive by a house on my way to work that has a beautiful hardy hibiscus out front with dinner-plate sized, white-and-red blossoms on it. Talk about flower envy! I’m hoping our Southern Belles eventually mature to that size.
There are many varieties, but a couple of interesting ones are “Kopper King,” which has coppery colored leaves and 12-inch-wide flowers in pink or white with red centers – talk about a dinner plate! If you want to attract hummingbirds, try “Cranberry Crush,” which has irresistible red flowers.
This is my last column for this year. I want to wish you all a safe and cozy winter full of seed catalogs and inspirational gardening books. See you in the spring!