Burnet

Burnet: how do you recognise it?

Habit

A clump of pinnate leaves topped by slender, branched flower stems up to 1.5 m; about 60 cm wide.

Leaves

Pinnate, with narrow, oblong, toothed leaflets; fresh green to slightly blue-green.

Flowers

Long, cylindrical spikes of tiny flowers without petals, first upright and then arching and drooping, from July to September.

Colour

White in ‘Alba’, pink in ‘Pink Elephant’ and deep reddish purple in ‘Purpurea’.

Roots

A sturdy, deep rootstock; the clump widens slowly but does not spread aggressively.

Flowering: July–September · Plants: March–May and September–October · Pruning: March

Why grow it?

• Adds height and movement to a border without taking up space: the stems are airy and you can see through them.
• Late flowering from July to September, when many perennials are over.
• Bees visit the flower spikes until late summer.
• Elegant pinnate foliage that forms an attractive clump from spring onwards.
• The faded spikes stand for a long time and look lovely covered in frost.
• Fully hardy and one of the best tall perennials for moist soil.

Burnet: where does it grow best?

• Sun or partial shade; in sun the stems stay sturdier and flowering is more generous.
• Loam, clay or peaty soil, rich in humus, acid to neutral.
• Moist to wet: it dislikes drought, especially in full sun.
• A spot that is not too windy, or among other plants that give the tall stems some support.
• Allow 50–60 cm per plant; lovely in groups of three or among ornamental grasses.

Light

Sun and partial shade

Soil type

Loam, clay or peat

Acidity

Acid or neutral

Moisture

Normal or wet

Size

1.5 m tall, 0.6 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Purple moor grass: An airy ornamental grass that likes the same moist soil.
• Joe Pye weed: Broad pink flower heads beside the drooping spikes, even in wet ground.
• Culver’s root: Upright candles that contrast with the arching spikes.
• Red bistort: Persicaria amplexicaulis flowers at the same time and fills the lower part of the border.
• Phlox: Scented panicles in July–August, in the same moist soil.

Burnet: when and how to plant it?

Plant in March–May and September–October.

1. Plant from March to May or in September–October, when the ground is not frozen.
2. Loosen the soil and work in a few spadefuls of compost.
3. Dig a hole well larger than the pot and set the plant at the same depth as it was in its pot.
4. Leave 50–60 cm between plants.
5. Firm the soil, water in well straight away and keep the soil moist for the first few weeks.
6. Spread a mulch of compost or leaf mould around the base.

Care

Watering

Water in dry spells, especially in the first year and in sunny spots.

Feeding

A little compost in spring is enough; too much fertiliser gives floppy stems.

Support

In a windy spot or very rich soil the stems may flop: put in a few canes in May or plant among sturdy neighbours.

Mulching

A layer of leaf mould in spring keeps the soil cool and moist.

Dividing

Rarely needed; every 4–5 years, when the clump becomes too big or flowers less.

Tip: Plant it among ornamental grasses or sturdy perennials: the tall, airy stems then get natural support and the drooping spikes are shown off at their best.

Burnet: when to prune it?

Pruning months: March.

When: Burnet needs hardly any pruning. Leave the stems standing over winter and cut them down in February–March, before new shoots appear.

How:

• In late winter, cut the old stems back to just above the ground.
• In summer, feel free to remove flattened or untidy flower stems; the foliage stays attractive.
• If the leaves are badly affected by mildew in late summer, cut them off: the plant will reshoot as normal in spring.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April, lift the clump and cut it with a sharp spade into pieces with a few buds each. Replant straight away and water well.

Seed

Sow in autumn in a pot left outside over winter. Seedlings of named cultivars do not always resemble the parent.

Burnet: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, to about −30 °C: no protection needed.
• Leave the faded stems standing: they look lovely with frost and insects overwinter in and under them.
• In a large pot: stand it in a sheltered spot and keep the compost slightly moist, even in winter.

Diseases and pests

• Powdery mildew: White powder on the leaves, especially after a dry summer. Water in dry spells and leave enough space between plants.
• Flopping stems: Usually caused by too much shade, fertiliser or wind. Give support or move the plant to a sunnier spot.
• Slugs: They eat the young leaves in spring. Pick them off in the evening.
• Brown leaf edges: A sign of drought. Water generously and mulch the soil.

Through the year

• March: Cut down old stems. Add compost. Plant and divide.
• April: Plant. Mulch. Watch for slugs.
• May: Plant. Put in supports in a windy spot.
• June: Water in dry spells.
• July: Flowering begins. Water in dry spells.
• August: Full flower. Water in dry spells.
• September: Last flowers. Plant.
• October: Plant. Sow seed in a pot left outside.
• November: Leave the faded stems standing for winter.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• Burnets have no petals: the colour of the spikes comes from the sepals and stamens.
• Its relative salad burnet (Sanguisorba minor) is a kitchen herb with a fresh, cucumber-like taste.
• The native great burnet (Sanguisorba officinalis) is the food plant of the scarce large blue, a rare butterfly.