How to prevent aphids from attacking nasturtiums
Q I love nasturtiums for their bright, sunny blooms. It’s disappointing to see their appearance ruined by black aphids. Is there a way to prevent these infestations?
A: In most years, I can avoid infestations by sowing the seeds in small patches only, but throughout the garden rather than all in one or two sites. One gardening friend told me that no aphids appear on plants growing in full sun. Another uses coffee grounds, replenished every few weeks, in the plantings to deter aphids.
Q When is the best time to dig and divide dahlia tubers?
A: I dig and divide clumps of dahlia tubers in the spring, every few years, and leave them in the ground over the winter. Last winter brought an unusually long cold period that did kill off some dahlias, but usually, in a normal winter and in a well-drained site, they do survive at the coast.
When the tops have blackened with the first frost, cut the stems down and mark the site of each clump. Identify each one, with the variety name if you have it or with the plant height and flower colour. I usually make a mound of soil over each dahlia clump and for easy visibility and a little extra protection, I top the soil with a shallow layer of aged sawdust or wood shavings.
In the spring, when the soil is no longer wet and has begun to warm — usually in April — dig up the clumps. Look for nubs of growth at the base of the old stem. When dividing a clump, make sure that each tuber you keep for replanting has a piece of stem with a growth bud.
Prepare planting sites ahead of time if possible, digging the soil over deeply and mixing in lime, compost and fertilizer. Plant most types around 12.5 cm deep, a little deeper for tall, top-heavy plants. Before filling in the planting hole, insert a stout stake for tall dahlias.