Whether you buy your vegetable and annual plants from the garden centre or whether, like me, you grow them from seed on the windowsill, all plants need hardening off before they can be safely planted outside.

And, although it sounds like a tough training regime, all that hardening off means is allowing plants to get used to progressively cooler temperatures.

Plants that experience sudden cold conditions can have their growth severely checked - in extreme cases they may be damaged so badly that they never recover sufficiently to make full grown plants.

The solution is simple gradual hardening off. Here at home I have three staging posts for seed-raised plants. They germinate on the dining room windowsill, where day temperatures are around 20C and night temperatures do not fall below 10C.

Once the seedlings are ready to be potted on I move them to the verandah, a heated, lean-to greenhouse attached to the side of the house, where temperatures vary between 25C max and 5C min.

When the little plants have been in the verandah for a few weeks they are transferred to the greenhouse, which has no heating and where temperatures at night are just a few degrees above those outside.

From there they can be planted out into the garden, though I usually check the weather forecast for imminent cold snaps before I risk my plants to the outside world.

Not everyone has the luxury of a greenhouse, but plants can be hardened off by taking them outdoors during the day and bringing them in again in the late evening. After about a week of such treatment they can safely be left out on all but the coldest of nights.

Alternatively you could construct a simple cold frame, using a sturdy box topped at night with a sheet of bubble polythene. Remember that half-hardy and tender plants should not be planted out until all danger of frost has passed. In all but the most sheltered parts of Cumbria this is usually around the last week in May.

On a completely different note, I can't let spring pass without mentioning Caltha palustris var. palustris. This oversized, North American relative of our native kingcup or marsh marigold has flowered for weeks in our bog garden, its rich, golden-yellow flowers easily outclassing the daffodils and its bright green, heart shaped-leaves apparently resistant to damage by slugs and snails. At up to 24in tall and 30in across, it makes a fine specimen.

Jobs for the gardener this week:

Pot up rooted cuttings taken in the last couple of months, and pot on seedlings regularly as they grow.

Mulch around fruit trees and bushes with well-rotted manure or garden compost.

Plant water lilies and aquatic plants.