Ciscoe Morris, Seattle Times Garden writer, talks about which perennials should be divided and which should be left alone. When the ground remains 40 degrees, it's time to start planting Dahlias, Gladiolus, Colocasia and the more exotic types of Canna in black nursery pots. Place them in front of a sunny south wall and tend...
A perennial usually needs dividing when it begins to thin out in the center, or when it no longer blooms as well as it used to. Not all perennials need dividing, however.
Peonies are easy to divide if you want to make new plants, but they never need dividing and left alone will continue to bloom prolifically for years. On the other hand, other perennials resent root disturbance, and are fairly impossible to divide without murdering them.
Perennials that are best left unmolested include Aruncus dioicus (goat’s beard), Cimicifuga (bug balm), Eryngium (sea holly), Gypsophila (baby’s breath), Aconitum (monks hood) and Baptisia (Indigo).
Although it’s rarely necessary to divide Kniphofia (torch lily), it’s relatively easy to remove sections to create new plants without harming the fine-leaved, repeat-blooming hybrids such as “Primrose Beauty” and “Shining Sceptre.”
Most Read Life Stories
It would be almost criminal to try to divide Kniphofia caulescens, and risk the life of such a sensational plant famous for its 3-foot-tall Agave-like structure; bold, bluish evergreen leaves; and immense orange and yellow flowers.
It’s time to plant some summer bloomers
Most of the tropical plants that grow from semihardy root structures such as Dahlias, Gladiolus, Colocasia and the more exotic types of Canna won’t survive if they’re left in the ground over winter. The best time to bring them out of storage and plant them is in spring, after the soil has warmed enough to remain above 40 degrees.
To get these plants off to a faster start, plant them in black nursery pots and place them in front of a sunny south wall. Water carefully, as black plastic heats up and the soil can dry quickly. Fertilize regularly with a good soluble houseplant fertilizer as soon as growth begins.
By the time they’ve developed a strong root system and are ready to plant out into the garden, they’ll be at least a third larger than they would have been had you planted them directly into the ground.
Drought-tolerant beauty for your spring garden
Pacific Coast Iris is the collective name for a number of diverse species of iris native to our region that produce extraordinarily beautiful flowers in spring, yet share the unique ability to thrive in our cold, wet winters and bone-dry summers with little or no supplementary watering.
In the past, these great plants were hard to come by, and if you were lucky enough to find them, few varieties were available. That’s no longer the case. Exciting new hybrids featuring beautifully patterned flowers ranging from soft pastel pink to deep purple to sunshine yellow are showing up on the shelves of local nurseries.
Here are some exceptional cultivators to look for: Iris x pacifica “Luminous Yellow” sports huge orange-yellow flowers held above 18-inch-tall evergreen leaves. Iris douglasiana “Burnt Sugar,” eventually capable of forming a 3-foot-wide clump of 1- to 2-foot-tall leaves, blooms for almost a month with large flowers of rich ocher and maroon.
If you’re looking for something for the front of the border, Iris innominata “Purple Form” has glossy leaves that grow only to 8 inches tall and are prolifically crowned with blossoms of deep purple.
Plant Pacific Coast Iris in full-sunshine and well-drained soil, and they’ll produce lasting beauty for years to come.
Ciscoe Morris: ciscoe@ciscoe.com. “Gardening with Ciscoe” airs at 10 a.m. Saturdays on KING-TV.