Dahlias, available in different colours, sizes and shapes, are gorgeous garden plants.

Blooming through summer and into autumn, they suit most garden styles, and smaller types can even be grown in containers.

With their blooms now fading, Monty Don has urged gardeners to keep deadheading them.

In an October blog post, Monty wrote: “Keep deadheading throughout October, particularly the equatorial plants like dahlias.

“This will extend their flowering season and squeeze the last bloom from them.

“Spent dahlia flowers can be tricky to differentiate from unopened buds but there is a foolproof difference.”

When they have finished flowering, they become pointed and cone-shaped, whereas the unopened buds are rounded.

It is recommended to deadhead dahlias regularly, ideally weekly throughout the entire growing season.

This ensures they are putting all of their energy into making flowers rather than seeds.

To deadhead, simply remove each spent flower, cutting back to a leaf joint lower down the stem.

Dahlias in full flower can be top heavy, especially in rain, so all but the dwarf types need support, according to the Royal Horticultural Society (RHS).

They said: “Dahlias with large, multi-petalled flowers need stout posts for support, one per stem. Tie in the flower stems as they grow.

“With smaller-flowered dahlias, strong bamboo canes should be sufficient, either singly or four in a square around the clump, with twine looped around the outside.”

In the winter, foliage will be killed off by frost, so it is important to either leave frosted plants in the ground or dig them up and store the tubers in a frost-free place over winter.

The RHS noted: “If you’ve grown plants from seed, these will have developed tubers by the end of the season, which can also be left in situ or stored indoors.

“As seed-raised plants are genetically variable, only choose the best to keep.”

If they become overcrowded next June or July, the RHS recommended lightly thinning them out to improve the overall display.