Giving perennials the best start
Plant container-grown perennials at any time of year, but avoid planting during frosty weather, in spells of prolonged drought (the plants will fry unless you are a slave to the watering can) or in winter in heavy clay soil (the plants will drown).
Plant bare-root perennials (and that includes your own divisions) in the autumn or spring months.
Enrich the earth with a generous supply of organic matter (well-rotted compost or manure) before you plant, give the ground a good dusting of blood, fish and bonemeal for good measure, and remove all perennial weed roots.
Dig a hole just large enough for each plant’s roots and firm the earth back, making sure that the crown of the plant (where roots meet shoots) is level with the surface of the soil. Do not plant too deeply.
Water the plants well, then spread a 5cm mulch of chipped bark, compost or manure on the surface of the soil, taking care not to swamp the plants themselves. This will hold in moisture and keep down annual weeds.
Firm back the earth around the plants after frost and do not allow them to go short of water in their first summer.
Stake taller varieties with twiggy pea sticks or wire plant supports before they need it. There is nothing worse than a trussed up perennial that has been staked too late in the season.
Cut back herbaceous perennials right to ground level in late autumn. Do not leave an inch or two of stalk behind, which will cut your fingers when you come to work with them the following spring. Compost the faded stalks.