In late spring when all frosts have finally finished, plant your bedding outside in pots, window boxes, or hanging baskets.
Saturate clay pots
Before planting up terracotta pots, soak them with water. Terracotta is porous, and saturating it first helps prevent the clay from drawing moisture out of the soil when the pot is planted up.
Add drainage material
Place a layer of broken clay pot pieces in the base of each pot to ensure good drainage. To reduce the amount of soil needed for larger pots, fill the bottom third of the container with pieces of plastic or broken pot instead.
Fill each container to about 2 in (5 cm) from the rim with all-purpose soil. Mix slow-release fertilizer designed for container plants into the soil. You can also add water-retaining gel crystals, which help keep the soil moist, reducing the need to water as frequently.
In this scheme the dahlias are the tallest, and should be planted at the back, while the dwarf French marigolds need to be at the front, with the other plants dotted in–between. Plant up, firm the plants in gently, and water them well.
Lift the plants
Water the young plants in their modules and leave to drain. Then gently squeeze the bottom and sides of each cell to loosen the rootballs, and remove the plants. Place them on the soil about 4 in (10 cm) apart.
Place the pots in a sunny position and water the plants regularly. Deadhead frequently to keep them in bloom for longer, removing faded flowers with clippers. Young plants are prone to attacks by snails and slugs, so apply a few slug pellets, use nematodes or fix a copper band around the pots to keep them at bay. A gritty mulch may also help to deter pests. To retain moisture in the soil, you can add a decorative mulch, which will also help to set off the planting.