How to grow plants from seed for plenty of summer colour

Annual plants are those which grow, flower, and set seed and die all in one year. They are synonymous with summer – think of cornflowers, sweet peas, love-in-a-mist, and sunflowers. If you start your planting in spring, you will have armfuls by summer.

What you will need:

• Seed trays – the ones with compartments are the best. Cardboard ones are even better as they can be planted straight into the garden. For sweet peas, use the centres of old toilet rolls

• Seed compost

• Horticultural sand or vermiculite (optional).

The other vital components for successful germination are warmth, fresh air and moisture. The next obvious step is to select which seeds you want to grow. Remember to think about colour, height and flowering times when planning. The seed packet will be marked as “perennial”, “annual” or “half-hardy annual”. When you want plants that will flower this year, it is the latter two categories you need to buy.

For many seeds – true annuals – the warmth of the sun on the earth as the days grow longer is enough to spur on germination. To sow these, you simply need to weed the area where you want the plants to grow, then rake the soil to break it down until it has a fine and even surface. Then you simply broadcast the seed. The problem with this method, especially for new gardeners, is that you may then not know what is a weedling and what is a seedling once growth starts, so you may like to sow in seed trays, which you can leave outdoors. Others, the “half-hardy” annuals, need an extra boost of heat by being grown indoors until all danger of frost has passed, when they can be transferred out of doors. You do not need a greenhouse, fancy heated pads or any special kit – a sunny windowsill will do, or a space on any surface near a window.

Some seeds need a bit of special treatment before sowing. For example, sweet peas have a very hard shell and need to be soaked for a few hours or overnight before planting. The seed packet will provide instructions.

Fill your seed trays with seed compost. The reason we use seed compost is that ordinary compost is too rich for young plants. Water the compost before you start sowing. How you sow depends on the size of the seed. If the seeds are large, like peas, beans or sunflowers, pop one seed firmly into the soil of each module or pot. For tiny fine seeds like opium poppies or snapdragon, you will need to sprinkle them very carefully on the top of the soil, trying not to get too many in one spot. I usually cover fine seeds like this with a dusting of horticultural sand or vermiculite to hold them in place.

Annuals to grow

• Cosmos

• Nicotiana (tobacco plant)

• Tagetes (French marigold)

• Zinnia

• Amaranthus

• Nigella

• Verbena x hybrida

• California poppy

• Shirley poppy

• sweet pea

• sunflower

• cornflower

• snapdragon

This feature originally appeared in the spring/summer 2024 issue of IMAGE Interiors. Have you thought about becoming a subscriber? Find out more, and sign up here.