How to store

You may receive your dahlia tubers from January onwards, weather permitting.
Please unpack immediately and store in a cool, frost free, dry place with plenty of air flow to avoid them rotting until you are ready to plant. Be careful keeping them in sheds as they may freeze or get eaten by mice or rats. It is very important you keep them safe until you are ready to plant.

When to plant

As dahlias are tender, you’re best starting the tubers into growth in the greenhouse, then plant them in their flowering site after the frosty days are passed. For most in the UK, this is at the end of May, but in Scotland this is more typically a bit later. (For an alternative method, see Planting dormant tubers below).

How to plant

Improve your soil by adding organic matter, such as home-made compost or well-rotted manure, over the area you’re planting in. Dig in some organic matter or a general purpose fertiliser as you plant.

• Tubers with shoots/potted tubers with shoots: Space about 60cm apart; planting so the tubers are 10-15cm deep
  
• Rooted cuttings growing in pots: Space a little closer at 50-60cm apart. Planted so that the top of the compost in their pots is just a little (few mm) below the soil level.

Mulch after planting to conserve moisture.

New shoots are vulnerable to slugs, aphids and even mice, so protect plants in their early stages of growth.

Planting dormant tubers

If you have purchased a tuber this year or if you lifted and stored your dahlias last year, but in spring don’t have the space to start them growing in pots in a greenhouse, you can plant them out directly into their growing place as dormant tubers in mid to late April. The soil won’t freeze at that point in the year and the tubers will start to make roots. By the time shoots come up in early June, the danger of damaging frost will be over. They’ll just be a little way behind plants started off in a greenhouse.

Staking

If your dahlia flower heads are large, you can put in stout posts, one per stem, and tie in these stems to stop plants flopping with the weight of the flowers. For smaller-flowered dahlias, you can put in bamboo canes (say at the four corners) and make a surrounding support basket with twine. Dwarf bedding dahlias won’t need staking.

Watering

Dahlias need watering in dry and hot weather. Direct your can or hose to the base of the plant. Soak down to the roots once a week rather than watering shallowly more frequently.

Feeding

Apply granular, general purpose feed at planting time. Liquid feed at fortnightly intervals from early July to early September with a high-potassium feed, like tomato feed, to boost flowering. In summer containers, feed as you do your other container plants, usually weekly.

Deadheading

As flowers fade, deadhead them, cutting back the stems to a leaf joint. You will find older flowers have tatty petals at the back. Deadheading regularly (weekly) will encourage plants to produce more flowers.

End of season care

After a productive summer and early autumn, flowering inevitably slows down as temperatures drop. Dahlia foliage will be killed off by frost, but even before then, through October and November, the flowers get increasingly tatty and windblown.

At the end of the season, you can either:

• Leave in situ. Cut down stems and cover the tops of tubers (crowns) with a good 15cm (6in) of coarse mulch, like bark chip or garden compost, to protect from frost. This is a good option if you live in warmer parts of the country and have free-draining soil. Although there’s always a risk of cold loss, it avoids the job of lifting and saves on storage space indoors.
  
• Dig up and store tubers. This is the way to go if you grow on wet winter soil and live in colder parts of the country. Cut down the stems and lift the tubers. Shake off as much of the soil as possible and trim off any damaged tubers. Cut the stems back to about 5-15cm and store the tubers in shallow crates or open topped boxes. Surround them with an insulating material like dry potting compost or sand just over the crowns. ­It’s best not to split tubers at this point as it’ll make wounds which are vulnerable to rotting. Do this, instead, in spring when you’re about to set them off into growth.
  Store your tubers in a dark, cool but frost-free place like a shed or garage. During really cold spells put some fleece or newspaper over the top for added protection. Check them occasionally for signs of rot and remove any unhealthy ones.