Giant scabious

Giant scabious: how do you recognise it?

Habit

Broad clump of large leaves, topped with airy, branched flower stems up to 2 m tall; the plant grows about 1 m wide.

Leaves

Large, pinnate and deeply cut, with toothed segments; dark green, mainly at the base of the plant.

Flowers

Flat flower heads 5–6 cm across, pale sulphur yellow, with larger outer florets as in scabious. From June to August.

Fruit

Round, bristly seed heads that turn brown after flowering.

Roots

A sturdy, woody rootstock with deep roots: once established it copes well with drought.

Flowering: June–August · Sowing: March–April · Plants: March–April and September–October · Pruning: August–September

Why grow it?

• One of the tallest border perennials, yet airy and see-through.
• Its soft, pale yellow goes with almost any other colour.
• Bees, bumblebees and butterflies visit the flowers for three months.
• Long-lived, hardy and undemanding about soil.
• Beautiful as an airy screen or as an eye-catcher at the back of a large border.

Giant scabious: where does it grow best?

• Full sun; in partial shade it flowers less and flops.
• Sand, loam or clay, acid to chalky, as long as it drains well.
• Dry to moderately moist; once established it is tough.
• Give it room: allow 1 m per plant, at the back of the border or as a loose specimen.
• A spot that is not too windy helps keep the tall stems upright.

Light

Sun

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Dry or normal

Size

2 m tall, 1 m wide

Hardiness

Hardy (to -35 °C)

Goes well with

• Delphinium: Blue spikes that stand out beautifully against the pale yellow.
• Bee balm: Red and pink flowers in the same summer border.
• Giant feather grass: Another airy, see-through plant, with golden spikelets.
• Globe thistle: Blue globes for the same sunny spot.
• Coneflower: Carries on into late summer, after the scabious has finished.

Giant scabious: when and how to plant it?

Plant in March–April and September–October.

1. Plant in March–April or in September–October.
2. Dig a wide, deep hole and loosen the bottom well for the deep roots.
3. On heavy clay, mix some coarse sand or grit and compost into the planting soil.
4. Set the plant at the same depth as it was in the pot and keep about 1 m from other plants.
5. Water well straight away and then regularly until it is established.
6. A thin mulch of compost keeps weeds down while the young plant grows.

Care

Water

In the first year during dry spells. After that rarely needed, except in long, hot droughts.

Feeding

Not needed; a layer of compost in March is enough. Too much fertiliser makes the stems floppy.

Support

Usually not needed in sun. In a windy spot or rich soil, put a few sturdy canes around the clump in May.

Deadheading

Remove spent flower heads for a longer display and fewer seedlings.

Space

Allow for the broad clump of leaves: do not plant low plants too close to its base.

Tip: Put it at the back of the border, or in the middle of a large border as a see-through plant: you can look through its airy stems. Give it at least 1 m of space and no fertiliser.

Giant scabious: when to prune it?

Pruning months: August–September.

When: After flowering, in August–September, cut the flower stems and old leaves back to just above the ground.

How:

• During flowering, cut spent heads back to the next side shoot.
• After the last flowers, cut all stems down to the ground; a fresh clump of leaves often follows.
• To collect seed, leave a few stems until the seed heads are brown and dry.

Caution: If you leave all the seed heads, it may self-seed in a warm spot.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Sow indoors in small pots in March–April, at room temperature. Prick out the seedlings into individual pots and plant them out in autumn. They usually flower from the second year.

Division

In March–April, lift a young clump and divide it with a sharp spade. Old clumps are woody and hard to divide; sowing is easier then.

Giant scabious: how does it get through the winter?

Hardy to −35 °C.

• Very hardy, to about −35 °C: no protection needed in Belgium.
• The top growth dies back and the plant regrows from the rootstock in spring.
• Heavy, wet soil in winter is the main risk: make sure drainage is good.

Diseases and pests

• Powdery mildew: White powder on the leaves in late summer, especially in dry weather. Cut back after flowering; the new leaves are usually healthy.
• Aphids: On the young stem tips in spring. Spray off with water or leave them to ladybirds.
• Slugs and snails: They eat the young leaves in spring. Pick them off in the evening.
• Falling stems: In rich soil, in shade or in strong wind. Do not feed, choose a sunny spot and put supports in place in good time.

Through the year

• March: Sow indoors. Plant or divide. Add compost.
• April: Sow indoors. Plant. Watch for slugs and aphids.
• May: Put supports in place in a windy spot.
• June: Flowering begins. Plenty of bees and butterflies.
• July: Full flower. Deadhead.
• August: Flowering ends. Cut back the stems or let seed ripen.
• September: Cut back. Plant. Plant out seedlings.
• October: Plant.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Butterflies

Nectar for butterflies.

Did you know?

• Cephalaria comes from the Greek kephalē, head, after its rounded flower heads.
• It used to belong to the teasel family, together with scabious and teasel; that family is now included in the honeysuckle family.
• Despite its 2 m height, it is a true perennial that comes back from the ground every year.