Storing plants over winter

Tender plants in the herbaceous border won't normally survive our low winter temperatures. To keep replacing plants every spring can quickly become expensive. If you don't have a greenhouse, conservatory or space in the house to protect the plants, here are some ideas to safely store your investment, ready for planting in the spring,

Pelargoniums (often referred to as geraniums)

In late October/early November, dig up the plant or remove from hanging baskets/patio planters.
Put it in a paper bag, allowing the soil to dry out completely. Remove the dry soil as it drops off the root ball. You'll also find that any remaining flowers and leaves will fall off.
Loosely tie the top of the bag with string and store in the shed, porch or conservatory.
Check the plant regularly. If the stems begin to shrivel, mist with a water spray.
If there's signs of mould, open the bag, allowing any moisture to escape.
In the spring, plant up, water well and cut the stems to 6ins (15cm).

If you've do have a greenhouse or lean-to, you can leave the plants in their pots, trim them to a short stem, removing all of the leaves and flowers. Keep the soil on the dry side.

If you've a conservatory or porch, bring them indoors in their pots and they should continue to flower through the winter.

Begonias (tuberous)

In early October reduce the amount of watering. When the foliage turns brown, lift and store the tubers/corms in a seed tray filled with dry sand. Replant in the spring when they send out new shoots. If the tubers are more than a few years old, they will have grown quite large, wait until the spring before splitting them. To split them, plant them up in the greenhouse as normal in early spring (late March/early April). As the temperature rises they will start to send up new shoots. Lift and cut the corm so each piece has a shoot. Leave the cut to dry/callous over for a couple of hours, before replanting each piece in a separate pot. Keep protected until all danger of frost has passed.

Canna lilies

Lift cannas after the flowers have gone over, remove any damaged part of the plant, loosely tie a label around the stem and lay in trays of used compost. Keeping them away from frost and the damp.

Zantedeschia (Calla lily)

Keep them frost-free over winter and don't water. Start to water them the spring and they'll bounce back into life.

Dahlias

Dig up dahlia tubers after flowering or after the first frost.
Cut any stems to 6ins (15cm).
Dry out the tubers by placing them upside down in a dry cool place for a couple of days.
Remove any soil (the root tubers be washed in a bucket of water and left to dry), any diseased or damaged spots, trimming and tidying any fibrous roots. Place roots down into a seed tray or shallow box, covering with dry horticultural sand (not orange builders sand, which contains lime and salts).
Label each tuber, or keep varieties/cultivars in separate labelled seed trays.
Store them in a cool place. Don't water though the winter, unless the tubers start to shrivel.

[Update]: Recent trials have found that it isn't necessary to lift and store Dahlia tubers, unless you live in an area that is susceptible to cold, wet weather. They will survive left in situ with a mulch of compost or straw covering them. Remember to put slug pellets down in the spring, to stop slugs eating the new shoots. Note, this trial was done over a relatively dry winter. Wet freezing winters may still kill plants left in the ground, so it might be worth saving a few plants using the method above.

Chrysanthemums

Treat in the same way as dahlias, except put them in a tray of moist soil/compost, rather than sand.
Keep the soil moist, but not wet.

Chrysanthemums can be propagated by starting over-wintered plants off early in a warm greenhouse, when the shoots are a couple of inches long cut them off the main plant at the base, remove bottom leaves and plant in a tray filled with potting compost, water lightly and keep them in a warm, shady position.

Storing seed

Seeds will start to germinate or deteriorate rapidly in moist conditions. Keep them in a dry, air tight container in a cool, dark location.