Getting Ready for Baskets and Containers

If you are looking to create your own baskets, containers or bedding displays then now is the time to start sowing seed indoors.

Many plants suitable for these displays are half hardy or tender annuals and perennials which we grow as annuals in the UK because of the climate. To get them ready to flower in the summer means starting seed off early to allow the plant to grow in a protected environment before planting up and hardening off ready to position outside after the last frost in your area which is usually about the end of May.

Flowers such as Geraniums (Pelargoniums), Begonias, Bacopas, Petunias and Lobelias are in this category and can give vibrant displays throughout the summer from May until the first frosts in October. If you are considering sowing from seed, consider whether you can give them consistently warm temperatures both day and night to allow them to germinate, enough bright light - but not direct sunlight, and enough space when they are potted on into individual pots or cell trays and require temperatures of between 15-18C.

The flowers mentioned are all native to countries such as South Africa and Australia - temperate and sub-tropical areas and have similar requirements for successful germination:

Use clean, moist but well draining compost in seed trays. Adding Perlite will help to aid drainage. Finely surface sow the seed. Some seeds will come as pellets which are easier to handle and can be spaced easily. Check the moisture is sufficient to damp the pellet. Very small seeds such as Lobelia can be mixed with a little sand to make it easier to control the distribution of the seed.

Cover with a propagation dome, glass sheet or plastic bag until the seeds have started to germinate. This keeps it moist and reduces the likelihood of the compost drying out. Place in a warm, bright area out of direct sunlight. The warmth needs to be consistent overnight for successful germination. In a cold period it’s surprising how low night temperatures can get in the house if placed by a window.

Once the first seeds have germinated, and this may take slightly longer than the advertised germination times, depending on the conditions, then vent the dome or remove the plastic bag or glass sheet. Seedlings may die, known as ‘damping off’ if they are overcrowded and in too high humidity. These conditions are favoured by several fungi found in the soil and air that cause the disease. Keeping the seedlings aired during the day and covered at night and making sure they are not overcrowded and will reduce the likelihood of ‘damping off’ while the lid will retain warmth overnight. Keep the compost from drying out by occasionally watering the seed tray from the bottom by sitting in a shallow bowl or tray of tap water and then allowing the excess to drain off leaving the compost moist but not waterlogged. At this stage tap water is best as rainwater may contain the fungal spores that cause damping off.

Once the seedlings are large enough to handle - when they have grown 2-4 true leaves, pot them into small pots approx 5-7.5 cm (2-3 inches) diameter depending on the size of the seedling or suitable plug trays. Loosen the soil under the roots and hold a leaf to transfer the seedling into the new pot. The stems are too fragile to use and will easily break.

Grow on in a light but not sunny place. Keep the warmth in place but gradually reduce the temperature they are in to about 15C-18C (59F-64.5F). About 6 weeks before the last frost in your area start to harden off the plants to acclimatise them to outdoor conditions. Start by putting out on warmer, drier days but make sure you bring them in at night. Increase outdoor exposure before transferring to their final position. Water well after transplanting. Check regularly as containers can dry out quickly. Also protect from slugs and snails and keep an eye out for any aphid infestations. In a few weeks you should have a colourful display to enjoy.