If you need to quickly cover a sunny fence or shed, or you just want to create height in a container display, annual climbers (or a tender perennial climber grown as annuals) are an ideal choice. Most will produce between 1.2-2m (4-7ft) of growth over the summer, draping their supports in blooms.
Among the easiest to grow are Ipomoea (morning glories and Spanish flag) and Cobaea scandens (cup-and-saucer vine). However, these need warm positions to bloom quickly and profusely. A more reliable choice is Rhodochiton atrosangineus, which flowers prolifically and will even tolerate a sheltered north-facing patio. Other good choices include lablab, Eccremocarpus scaber (Chilean glory vine), Tropaeolum peregrinum (canary creeper), Thunbergia alata (black-eyed Susan) and don’t forget sweet peas.
Provide trellis or pea netting on a fence, wall or shed, but consider using ready-made obelisks or a wigwam of canes in containers. Wide containers provide the most stable base for tall supports.
Growing annual climbers
Young plants of annual climbers are increasingly available in garden centres, or they are easy to raise from seed. Most annual climbers are rapid growers, but dislike cool conditions which can cause stunting. As a result, it is best to sow them from early April to early May in a heated propagator or a warm windowsill. Fill modules or seed trays with a free-draining seed compost (use a 2:1 mixture of multipurpose compost and perlite). Level and firm the surface of the compost and then water well using a watering can with a fine rose attached. Allow the excess water to drain away before sowing
The seeds of annual climbers vary greatly in size and shape, but many of the commonly-grown types are large enough to handle, including morning glory, lablab and the cup-and-saucer vine. This makes it possible to sow the seeds individually in modules. Create a little indentation with a dibber or your finger in the compost and then place one seed in each hole before covering with vermiculite. The seeds of the cup-and-saucer vine are large and flat so are easily pushed edge-on into the compost. Small seed is best scattered evenly on the compost surface and just covered with vermiculite. Keep all sown trays and modules warm and moist until they germinate. Afterwards, remove the seedlings from the propagator and grow on in a frost-free greenhouse or on a windowsill.
Prick out the seedlings sown in trays when they develop their first adult set of leaves. Use 7.5cm (3in) pots of multipurpose compost.
When the plants begin to grow, support them by pushing a pea stick into the pot or module. They can be planted outside in a sunny spot or container after the last frosts – usually late May or early June and after adequate hardening off. A little later is usually better as they often sulk if it is cold. Keep containers moist but not soggy and apply a liquid fertiliser weekly after the first month to encourage good growth.