How to pre­vent aphids from at­tack­ing nas­tur­tiums

The Province - - HOMES - He­len Ch­es­nut

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.

— THE AS­SO­CI­ATED PRESS FILES

Ev­ery few years in the spring, He­len Ch­es­nut di­vides clumps of dahlia tu­bers and then leaves them in the ground over the win­ter.

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