Pickerelweed

Pickerelweed: how do you recognise it?

Habit

An upright clump 60–80 cm tall and about 60 cm across.

Leaves

Heart-shaped to lance-shaped, glossy dark green and firm, on long, thick stalks.

Flowers

Dense spikes up to about 15 cm long of small violet-blue flowers; the upper petal has two yellow spots. Each flower is short-lived, but the spike keeps opening new ones for weeks.

Fruit

Small green fruits with one seed each, ripening in the spike after flowering.

Roots

A thick, creeping rhizome that spreads slowly.

Flowering: July–September · Plants: May–June · Pruning: October

Why grow it?

• Blue flower spikes from July into September, late in the season, when few other pond plants are still in flower.
• Bees, bumblebees and butterflies love the flowers.
• The glossy, heart-shaped leaves look good all season and give structure to the pond edge.
• The clumps spread slowly and do not run riot.
• Takes up nutrients from the water and so helps to limit algae.

Pickerelweed: where does it grow best?

• Full sun; in shade it hardly flowers.
• Wet, fertile soil: loam, clay or peat, acid to neutral.
• In shallow water, with 5–20 cm of water above the soil in the basket.
• Allow about 60 cm per plant; within a few years one plant fills a basket.

Light

Sun

Soil type

Loam, clay or peat

Acidity

Acid or neutral

Moisture

Wet

Size

0.8 m tall, 0.6 m wide

Hardiness

Hardy (to -20 °C)

Goes well with

• Yellow flag: Yellow flowers in May–June, before pickerelweed starts to flower.
• European white water lily: Floating white flowers on the deeper water alongside, in the same summer months.
• Arrowhead: A native marginal with arrow-shaped leaves and white flowers, for the same shallow water.
• Purple loosestrife: Purple spikes on the bank, also loved by bees and butterflies.
• Dwarf bulrush: Small brown heads and fine leaves beside the broad, glossy foliage.

Pickerelweed: when and how to plant it?

Plant in May–June.

1. Plant in May–June, when the water is warm enough: it is late to start into growth.
2. Use a roomy pond basket filled with heavy garden soil or clay-rich aquatic compost.
3. Set the rhizome just below the surface, firm in and top with a layer of gravel.
4. Place the basket so there is 5–20 cm of water above the soil; start young plants a little shallower.
5. Leave about 60 cm between plants.

Care

Watering

It must always stand in water. Top up the pond in dry summers, preferably with rainwater.

Feeding

Usually not needed. For a plant that has been in the same basket for years, push a fertiliser tablet for pond plants into the soil in spring.

Deadheading

Cut off faded spikes: it keeps the plant tidy and can encourage new spikes.

Dividing

Every 3–4 years, in May–June, when the basket gets too full.

Old foliage

In October, cut the dead foliage back to just above the water.

Tip: Be patient in spring: pickerelweed does not start growing until May, when the water is warm enough. So do not take it out of the pond too early, thinking it has died.

Pickerelweed: when to prune it?

Pruning months: October.

When: In October, when the foliage dies back. Otherwise it needs hardly any pruning.

How:

• Cut brown leaves and old flower stems back to just above the water line.
• Fish fallen leaves out of the water so they do not rot and pollute it.
• During flowering, cut off faded spikes to keep the plant tidy.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In May–June, as it starts into growth, lift the basket and cut the rhizome with a sharp knife into pieces, each with a few shoots and roots. Replant each piece straight away in its own basket.

Seed

Sow fresh seed in a pot of wet compost and keep it wet at all times. Germination is erratic and seedlings take a few years to flower.

Pickerelweed: how does it get through the winter?

Hardy to −20 °C.

• Hardy to about −20 °C, as long as the rhizome stays under water.
• In shallow water the rhizome can freeze in a hard winter: lower the basket to about 30 cm deep in autumn and raise it again in May.
• In a tub or mini pond: move the basket in winter to a cool, frost-free place, standing in a bucket of water.
• It starts late, often not until May: do not throw it out too soon in spring.

Diseases and pests

• Aphids: Black aphids on the young leaves and flower stems. Hose them into the water, where fish eat them.
• Late start: In April the plant still looks dead: that is normal. Wait until May–June before giving up on it.
• Frozen rhizome: A soft, rotten rhizome in spring, after a hard winter in shallow water. In future, lower the basket deeper for winter.
• Few flowers: Too little sun or an overcrowded basket. Move it to a sunnier spot and divide the clump.

Through the year

• April: No leaves yet: be patient, it starts late.
• May: Plant or divide. Raise the basket back to 5–20 cm deep. New leaves appear.
• June: Plant or divide. Watch for aphids.
• July: First flower spikes. Bees and butterflies visit the flowers.
• August: Full flowering. Cut off faded spikes. Top up the pond in dry spells.
• September: Last flowers.
• October: Cut dead foliage back to just above the water. Lower the basket deeper.
• November: Fish fallen leaves out of the water.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Butterflies

Nectar for butterflies.

Did you know?

• Its Dutch name, snoekkruid (‘pike herb’), refers to the pike. The English name pickerelweed also comes from the pickerel, a small American pike that lives among these plants.
• The genus is named after Giulio Pontedera, an 18th-century Italian botanist.
• The two yellow spots on the upper petal guide bees to the nectar.