8 ways to grow big, beautiful dahlias

As with daylilies and roses, growing dahlias tends to be habit forming because they are as beautiful in a vase as they are in a garden.

8 ways to grow big, beautiful dahlias

Dahlias deliver

Dahlias deliver brilliant colour for as long as warm weather lasts.

  • Dwarf types can be used to fill window boxes or edge sunny beds, or you can grow tall, large-flowered varieties if you prefer. Some produce blooms as big as dinner plates!

1. Give dahlias a head start

  • Plant the tubers in early spring in a warm (at least 16°C), sunny place, such as a sunroom or in pots kept by your patio doors.
  • Plant them in a shallow box filled with a light planting medium, such as seed-starting mix or light-textured potting soil.

2. The right depth

  • In the garden, larger dahlia varieties need a planting depth of 15 to 20 centimetres.
  • Dwarf types can be planted only eight to 10 centimetres deep.
  • Many gardeners plant dahlias in well-enriched planting holes and cover them with 2.5 centimetres of soil weekly as the stems grow.

Always wait until the last spring frost has passed to plant dahlias.

3. Double your dahlias

  • When the shoots of tubers reach 15 to 18 centimetres in length, cut them five centimetres above the soil line and set the cuttings to root in pots filled with seed-starting mix.
  • Enclose the potted cuttings in plastic bags and keep them warm.
  • In three weeks, they will root and you'll have twice as many dahlias!

4. Keep them well fed

Dahlias don't like to go hungry, so include a water-soluble plant food in the water you give them, or side-dress them monthly with a balanced granular fertilizer.

5. Stake inconspicuously

For tall dahlia varieties, stake when the stems reach 45 to 50 centimetres high.

  • Select three or four bamboo canes of the same height as the mature plant and drive them into the soil beside the main stems.
  • Tie the stems at two heights with soft twine and incorporate the new growth as it develops.

6. Storing them for winter

Don't tug on the stems when you lift dahlias.

  • Delicately lift the entire clump with a spading fork to keep from damaging the tubers.
  • Let the tubers dry in the open air for at least a day, preferably in the sun, before knocking off the dry soil and storing them for the winter.

7. Make sure to deadhead

  • Prolong flowering by deadheading.

When faded flowers are promptly removed, many small-flowered varieties will bloom nonstop for four months or longer.

8. Get big flowers

To get dinner-plate-size flowers, choose cactus- or decorative-type dahlias.

  • Remove the weakest stems, leaving only two or three of the strongest.
  • When the plants are about 30 centimetres tall, tie them to stakes.
  • As flower buds form, pinch them off or remove side shoots, leaving only the top bud.
  • Pros get blooms up to 25 centimetres in diameter.
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