Dahlia tubers overwinter best in fast-draining soil
Dear Helen: After reading one of your columns early in the year, I decided to grow some dahlias from seed. The plants have put on a fine show. Now I’m wondering how to treat them after frost kills off the top growth. Do I pull them up for the compost like annual flowers or will they regrow like perennials if left in place? F.G.
Over the course of the growing season your seed-grown dahlias will have formed clumps of tubers, which can be dug and stored or left in the garden.
Leaving the tuber clumps in place works most successfully in soils that are light-textured and porous enough to drain quickly of excess moisture in winter. The soil should also not be heavily populated with root-gnawing pests such as wireworms.
Clear away dead top growth after frost. Mark the planting sites with labels or stakes, and mulch with a little soil. I usually place a layer of wood shavings over my dahlia roots for the winter. The shavings (not cedar) help to mark the plants’ locations and insulate the tuber clumps. I lift and divide dahlia clumps every two or three years, in the spring.
If you choose to dig up the tuber clumps and store them, lift them carefully after frost (or late October to early November). Leave about a 10-centimetre length of stalk. Label the plants with their variety name and height. Place them on a clean, dry surface, cut stalk downward, to drain and dry for a few hours. Shake and brush excess soil off the tubers and store the clumps in boxes of sawdust or vermiculite, in a frost-free place ideally at about 5C.
Check the tubers a few times over the winter and spray-mist the storage medium lightly if the tubers show signs of shrivelling.
Dear Helen: What conditions in a garden help to shelter bees over the winter? J.S. Dear J.S.: Most kinds of bees have an annual life cycle, living for just the one year and leaving eggs or queens to overwinter and emerge the following year to start another generation. European honeybee hives carry on as communities with worker bees living less than a year but the queens lasting for as long as six years to create successive generations. They make nests in wood cavities found in a garden or in custom-built hives.
Bumble bees look for dry places with insulating materials like sheltered piles of leaves to hibernate in. Queens emerge very early in spring and look for nesting sites such as abandoned rodent nests, rock cavities, bird houses, even compost piles.
Native blue orchard mason bees make nests under bark and in rotting wood, holes in trees, and hollow stems. As with the other two bees, having old and rotting wood in the garden provides potential nesting and wintering places. Leave some deadwood and hollow-stemmed plants in the garden, or set up a blue orchard mason bee condo, available commercially.
The condos are a collection of tubes in which the females stash pollen and nectar with individual eggs, each sealed in its own compartment with clay and soil walls Hence the term mason bee.
These bees emerge when plum and cherry trees start to blossom, usually in March when temperatures reach 14 C. They eat, mate, and establish nests for four to six weeks before dying off. Activity is finished by June. Bee condos are placed out before their active season begins.
GARDEN EVENTS
HCP courses. The Horticulture Centre of the Pacific, 505 Quayle Rd. in Saanich, is offering the following courses. To register, call 250-479-6162. hcp.ca. • Herbs to Beat the Winter Blues with Lily Fawn, Sunday, 1 to 3:30 p.m. Make and take home tinctures, oils and teas. Cost for HCP members $55, others $65. • Growing Medicinal Mushrooms with Danielle Stevenson, Oct. 26, 6 to 8:30 p.m. Members $50, others $60. • Bean Pot Basket Workshop with Joan Carrigan, Oct. 29, 9:30 a.m. to 4:30 p.m. Members $115, others $135. • Permaculture Basics with the Compost Education Centre, Oct. 29, 10 a.m. to 12 p.m. Members $18, others $25.