Trifid bur-marigold

How to recognise it

Growth form

Annual, 15–100 cm, upright and often much branched; small on poor ground, broad and bushy on rich mud.

Leaf

Opposite, 5–15 cm, usually deeply divided into three to five coarsely toothed lobes; the leaf stalk is winged. Sometimes undivided on small plants.

Flower

Upright, button-like heads of 1.5–2.5 cm with brownish-yellow disc florets, rarely with short yellow rays. Beneath them 5–8 long, green, leafy bracts. Flowers in July–October.

Fruit/Seed

Flat, wedge-shaped, brown achenes of 6–8 mm with two to four bristles covered in downward-pointing barbs.

Stem

Hairless to slightly hairy, round, green to flushed purplish red.

Confusion with

Nodding bur-marigold has undivided leaves and nodding heads. Beggarticks, a non-native species from North America that is becoming more frequent, has pinnate leaves with three to five clearly stalked leaflets and blackish-brown seeds; in trifid bur-marigold the leaf lobes are not stalked.

Flowering: July–October · Pruning: March

Why grow it?

• A late bloomer: from July into October it offers nectar and pollen to bees, bumblebees and hoverflies, when little else is still flowering.
• A pioneer of exposed banks: it grows where other plants struggle, on bare, wet mud.
• In autumn and winter its seeds are food for seed-eating birds.
• Attractive in late summer: stems and leaves often turn purplish red.
• A fine example of seed dispersal by animals: the seeds travel hooked into fur and feathers, just like burdock burs.

Trifid bur-marigold: where does it grow best?

• In the wild on exposed banks of ponds, lakes and rivers, along ditches and moats, on muddy field edges and in wet tall-herb vegetation.
• Full sun to light half shade.
• Wet, fertile, bare mud or clay that dries out in summer; it can stand being under water for a while.
• In the garden: on the gently sloping, muddy bank of a pond, where the water level drops in summer.

Goes well with

• Water-pepper: Another annual of exposed banks, with drooping pink spikes.
• Gypsywort: White whorls on the wet bank, also in late summer.
• Purple loosestrife: Purple-pink spikes on the same wet, sunny bank.
• Water mint: Lilac pompons and a fresh minty scent at the water’s edge.

Trifid bur-marigold: when and how to plant it?

1. Buy seed from a native seed supplier. Do not dig up plants in the wild; there is no need anyway, as it self-sows easily.
2. Sow in October–November or March–April on wet, bare mud at the water’s edge. Seed often germinates better after a cold winter.
3. Press the seed into the surface and barely cover it.
4. Leave 20–30 cm between plants, or simply let them go their own way.
5. Keep the spot open: it will not germinate in dense vegetation or reeds.

Care

Water

Keep the soil wet or muddy; on a pond edge that dries out in summer, this happens by itself.

Feeding

Not needed: it grows on fertile mud.

Bare ground

Scrape a patch of bank open every spring or let the water level drop in summer: without bare mud it disappears.

Spreading

It can self-sow freely on open mud. If there are too many, pull plants up before the seeds ripen.

Letting it seed

Let some of the plants ripen: as an annual it has to come up from seed again every year.

Tip: Give your pond a gently sloping, shallow bank without a visible liner edge or edging boards, where the water drops in summer: bur-marigold, water-pepper and other pioneers will appear on that bare mud by themselves.

Pruning and mowing

Pruning months: March.

When: Not really needed: it is an annual. Clear the dead stems in March.

How:

• After flowering, leave the plants until the seed is ripe and has fallen.
• Leave the dead stems standing over winter for birds and insects.
• Clear them in March, so the mud is bare and open again for new seedlings.

Caution: Wear gloves and old clothes if you work among ripe plants in autumn: the seeds hook into everything.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

The only way. In September–October pick ripe heads, let them dry and scatter the seeds on wet mud in autumn. It also self-sows.

Trifid bur-marigold: how does it get through the winter?

Hardy to −2 °C: protect in harsh winters.

• The plant dies at the first frost; the dry, brown stems with their heads stay standing.
• Birds pick seeds from the heads, and the seeds hook into fur and feathers: that is how they travel to new banks.
• The seed overwinters in the mud and germinates in spring as the soil warms up.

Diseases and pests

• Clinging seeds: The seeds catch on clothes, socks and the coats of dogs and cats. Comb pets after a walk along the bank and also check between their toes and in their ears.
• Crowded out: Reed, reed sweet-grass and other perennials take over the bank. Keep a patch clear every year.
• No bare mud: On a bank with a constant water level and dense vegetation it disappears. Let the water level drop or scrape the bank open.
• Beggarticks: Sometimes arrives with seed or soil and can crowd out trifid bur-marigold. Pull it up before the seed ripens.

Through the year

• March: Clear dead stems. Scrape the bank open. Sow.
• April: Seedlings germinate on the wet mud.
• May: Young plants grow. Pull up surplus seedlings.
• June: Rapid growth as the water drops.
• July: Flowering begins: bees and hoverflies.
• August: Full flower on the exposed bank.
• September: Flowers and ripe seeds. Check pets’ coats for seeds.
• October: Last flowers. Collect and sow seed.
• November: The plant dies back; leave the stems standing.

Did you know?

• Bidens means ‘two teeth’, after the bristles on the seed; tripartita means ‘three-parted’, after the leaves.
• Botanists have named a whole plant community after bur-marigold: the vegetation of exposed, fertile banks, with species such as water-pepper and marsh yellow-cress.
• The plant was once used to dye wool yellow to orange.