Canadian burnet

Canadian burnet: how do you recognise it?

Habit

Sturdy clump 1.5–1.8 m tall and about 60 cm wide, with upright, branching flower stems.

Foliage

Pinnate, with oval to oblong, toothed leaflets; green and slightly coarse in texture.

Flower

Long white bottlebrush spikes from August to October. The flowers have no petals: the white colour comes from the stamens.

Roots

Creeping rhizome that slowly widens the clump. Easy to divide in spring.

Flowering: August–October · Plants: March–May and September–October · Pruning: February–March

Why grow it?

• Flowers from August to October, when many borders are losing colour.
• The airy white spikes on stems 1.5–1.8 m tall add height and movement to a damp border or pond edge.
• Bees and other insects visit the flowers in late summer.
• Grows well in wet, heavy soil where many other perennials struggle.
• Fully hardy and low-maintenance: one cut back a year is enough.

Canadian burnet: where does it grow best?

• Full sun to partial shade; in full sun it needs more water.
• Moist to wet, humus-rich soil: loam, clay or peat, acid to neutral.
• Do not let the soil dry out in summer; wet feet are welcome, for example at a pond edge.
• Allow 50–60 cm per plant and place it between sturdy neighbours, because the tall stems can flop.

Light

Sun and partial shade

Soil type

Loam, clay or peat

Acidity

Acid or neutral

Moisture

Wet

Size

1.8 m tall, 0.6 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Hemp agrimony: Tall, late-flowering and happy in the same damp soil.
• Meadowsweet: Loves moisture; its frothy plumes flower earlier in summer.
• Purple moor grass: An airy ornamental grass that frames the white spikes.
• Purple loosestrife: Purple flower spikes in the same wet soil.

Canadian burnet: when and how to plant it?

Plant in March–May and September–October.

1. Plant in March–May or in September–October, when the soil is not frozen.
2. Dig a hole twice as wide as the root ball and mix in some compost or leaf mould.
3. Set the plant at the same depth as in its pot, with the top of the root ball level with the soil surface.
4. Leave 50–60 cm between plants.
5. Water thoroughly straight away and keep the soil moist in the first year.
6. Spread a layer of compost or leaf mould mulch around the plant.

Care

Water

Keep the soil moist at all times. Water generously at the base in a long dry spell; at a pond edge watering is rarely needed.

Feeding

A layer of compost in March is enough. Do not add extra nitrogen fertiliser: it gives long, floppy stems that fall over.

Mulching

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

Support

In a windy spot or rich soil the tall stems can flop. Sturdy neighbours or a plant support keep them upright.

Spent flower spikes

Leave them: they give structure in autumn and winter. Cut everything back in February–March.

Tip: Put it between sturdy neighbours such as hemp agrimony and ornamental grasses: they hold the tall stems upright. A damp spot with a layer of mulch prevents drought stress.

Canadian burnet: when to prune it?

Pruning months: February–March.

When: In February–March, before the new shoots come through.

How:

• Cut all dead stems and leaves back to just above the ground.
• Use sharp secateurs or shears and clear away the clippings.
• In summer, remove dead or broken stems at the base straight away.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April or September–October, cut the clump into pieces with a spade, each with roots and shoots, and replant at once. Dividing every few years keeps the clump vigorous.

Seed

Seed germinates best after a cold spell: sow in autumn in a seed tray and leave it outdoors until spring.

Canadian burnet: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, down to about −30 °C: no protection is needed in Belgian winters.
• Leave the dry stems standing until February: they give structure to the winter garden.
• Give plants set out in autumn a layer of leaves or compost as extra protection.

Diseases and pests

• Flopping: Tall stems bend after rain or wind. Place it between sturdy neighbours, add support and avoid over-rich feeding.
• Drought stress: Leaf edges turn brown and the plant wilts. Water generously and mulch the soil.
• Powdery mildew: White powder on the leaves at the end of summer, especially in dry weather. Water at the base and cut off affected leaves.
• Slugs: They eat young shoots in spring. Collect them in the evening and protect the new shoots.

Through the year

• February: Cut dead stems back to just above the ground.
• March: Cut back if not yet done. Add compost. Plant or divide.
• April: Plant or divide. Apply mulch.
• May: Plant. Put in plant supports. Watch for slugs.
• June: Water in dry weather; keep the soil moist.
• July: Water in dry weather.
• August: Flowering begins. Insects visit the spikes.
• September: Full flower. Planting still possible.
• October: Last flowers. Plant or divide.
• November: Leave the stems standing as winter decoration.
• December: Dormant.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The fluffy parts of the spikes are not petals but long stamens: the flowers have no petals.
• Like strawberry, apple and rose, it belongs to the rose family (Rosaceae).