Dahlia coccinea

Dahlia coccinea: how do you recognise it?

Habit

Upright, branching perennial of about 1.2 m high and 60 cm wide, with straight, often hollow stems.

Leaves

Green, finely divided (once or twice pinnate), in opposite pairs on the stem.

Flowers

Single, usually eight orange-red ray florets around a yellow disc, from July to October.

Bulb/tuber

Thickened tuberous roots that are lifted and stored in autumn.

Fruit

Dry seeds in the flower heads, which you can collect and sow next year.

Flowering: July–October · Sowing: March–April · Plants: May · Pruning: June and October–November

Why grow it?

• Long flowering from July until the first frost in October: plenty of colour in late summer and autumn.
• Single flowers full of pollen and nectar: a magnet for bees, bumblebees and butterflies.
• Airy, natural look that suits a prairie or cottage garden.
• Easy to grow from seed: flowers in its first year.
• Usable as a cut flower in a loose, colourful bunch, although the blooms last only a short time in the vase.

Dahlia coccinea: where does it grow best?

• Full sun; in shade it becomes thin and flowers poorly.
• Free-draining, fertile sandy, loamy or clay soil, neutral to chalky.
• Normally moist; water in summer in dry weather, but avoid wet feet, as the tubers rot.
• Sheltered from strong wind. Allow 50–60 cm between plants.

Light

Sun

Soil type

Sand, loam or clay

Acidity

Neutral or chalky

Moisture

Normal

Size

1.2 m tall, 0.6 m wide

Hardiness

Frost tender: lift the bulbs or tubers before the frost and store them frost-free

Goes well with

• Ornamental grasses: Soft plumes that make the orange-red glow.
• Sage: Purple flowers and silvery foliage at the same time.
• Coneflower: Suits a prairie bed and attracts the same insects.
• Verbena: Tall, airy purple plumes, attractive to butterflies.
• Rudbeckia: Yellow flowers that go well with orange-red.

Dahlia coccinea: when and how to plant it?

Plant in May.

1. Plant the tubers or young plants after mid-May, when there is no more night frost; sow indoors in March–April.
2. Dig a hole 15–20 cm deep and mix in a little compost.
3. Plant tubers 10–15 cm deep with the eyes upward; young plants at the same depth as in the pot.
4. Leave 50–60 cm between plants and put in a stake or support right away.
5. Water in generously and add a little mulch, but watch out for slugs.

Care

Water

In the first season and in dry weather water generously once a week at the base; not over the flowers.

Feeding

A few times in summer give a fertiliser for flowering plants; not too rich in nitrogen, or you get lots of leaves and few flowers.

Support

Tie the stems to a stake or grid, as the flowers are heavy and the stems can snap in wind.

Deadheading

Cut off faded flowers regularly: it keeps the plant flowering.

Pinching out

In June pinch out the tips of young plants above the third pair of leaves; this gives more side shoots and so more flowers.

Tip: Plant after mid-May, provide support and cut off faded flowers for a long display. Lift the tubers after the first night frost and store them dry and frost-free.

Dahlia coccinea: when to prune it?

Pruning months: June and October–November.

When: Pinch out the tips in June; cut the stems back after the first night frost, in October–November.

How:

• In June pinch out the tip of young shoots above a pair of leaves for bushy growth.
• Cut off faded flowers above a pair of leaves or a side shoot.
• After the first frost, when the foliage is black, cut the stems to 10–15 cm above the ground.
• Then carefully lift the tubers with a fork and leave them to dry.

Caution: Do not cut the stems before frost has killed them back, unless you are lifting the tubers straight away: they need the foliage to build up reserves.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Sow indoors in March–April in pots of seed compost, at about 18–20 °C. After a few weeks prick out, harden off and plant out after mid-May; they flower in the first year.

Dividing tubers

In spring divide the stored tubers with a sharp knife: each piece needs part of the crown with at least one eye.

Cuttings

In March–April take 5–8 cm shoots from the stored tubers once they have sprouted and root them in moist compost.

Dahlia coccinea: how does it get through the winter?

Hardy to 0 °C: protect in harsh winters.

• Not hardy: the tubers do not survive frost in the ground. Lift them after the first night frost.
• Dry them for a few days, put them in boxes with dry sand, peat or wood shavings and store them cool (about 5–10 °C), dark and frost-free.
• Check them now and then during winter: remove soft or mouldy tubers.

Diseases and pests

• Slugs: Young shoots are eaten bare in spring. Use barriers or collect them in the evening.
• Earwigs: They nibble flowers and leaves. Trap them with an upturned pot of straw on a stake.
• Aphids: On young shoots and buds. Rinse off with water or let the ladybirds work.
• Powdery mildew: White powder on the leaves in late summer. Allow space, water at the base and remove affected leaves.
• Tuber rot: Soft, mouldy tubers in winter. Dry well before storing and keep in dry material.

Through the year

• January: Check stored tubers.
• February: Check stored tubers.
• March: Sow indoors. Start tubers into growth if you like.
• April: Sow and prick out. Take cuttings.
• May: Plant out after mid-May and put in supports.
• June: Pinch out tips. Mulch and water.
• July: Flowering begins. Cut off faded flowers.
• August: Full bloom. Water, feed.
• September: Flowering. Collect seed.
• October: After the first night frost, cut back the stems and lift the tubers.
• November: Dry the tubers and store them frost-free.
• December: Rest, store the tubers.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Butterflies

Nectar for butterflies.

Did you know?

• The name coccinea means ‘scarlet’, after the bright colour of the flowers.
• The dahlia is the national flower of Mexico.
• The genus name honours the Swedish botanist Anders Dahl, a pupil of Linnaeus.