Missouri evening primrose

Missouri evening primrose: how do you recognise it?

Habit

Low, trailing clump 15–20 cm tall and up to 50 cm wide, with prostrate stems.

Foliage

Narrowly lance-shaped, 4–10 cm, dark green with a pale midrib.

Flower

Very large cups of 8–10 cm, opening mostly in the late afternoon and evening, from June to September.

Colour

Bright lemon yellow, with the pale midrib of the leaves as a contrast.

Fruit

Large capsules with four wings; the name macrocarpa means ‘large-fruited’.

Flowering: June–September · Plants: April–May · Pruning: March

Why grow it?

• Huge yellow flowers of 8–10 cm, from June into September, on a plant barely 20 cm tall.
• Drought-tolerant and suited to the sunniest, poorest spots.
• Flowers mostly in the evening: a plant that shines on summer evenings.
• Bees and moths visit the flowers; the big winged seed capsules are attractive too.
• A low, trailing habit that drapes beautifully over walls and edges.

Missouri evening primrose: where does it grow best?

• Full sun, in a warm, open spot, ideally against a south-facing wall or on a slope.
• Poor, very well-drained soil: sand or loam with grit, neutral to chalky.
• Dry: it tolerates drought well, but absolutely not permanently wet ground.
• Plant 40–50 cm apart; it spreads slowly.

Light

Sun

Soil type

Sand or loam

Acidity

Neutral or chalky

Moisture

Dry

Size

0.2 m tall, 0.5 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Stonecrop: Sedum likes the same sun and drought and sets off the yellow cups.
• Lavender: Grey-green, fragrant foliage in the same poor soil, with purple flowers.
• Fescue: Fine blue-grey tufts make a calm backdrop for the yellow flowers.
• Rock rose: A low, trailing bloomer that prefers the same dry, sunny soil.

Missouri evening primrose: when and how to plant it?

Plant in April–May.

1. Plant in April–May, when the soil is warming up and winter is over.
2. Dig a hole twice as wide as the root ball; on heavy soil mix in plenty of coarse sand and grit.
3. Set the plant at the same depth as in its pot, high and dry, with the crown just above soil level.
4. Keep 40–50 cm between plants.
5. Water in at once and mulch with gravel or coarse sand around the crown, not compost.

Care

Water

In the first year, water weekly in long dry spells; after that it almost always manages on its own.

Feeding

Not needed: soil that is too rich gives floppy foliage and fewer flowers.

Mulching

A layer of gravel around the crown keeps the plant dry.

Spent flowers

Remove spent flowers for a longer flowering, or leave a few seed capsules for their ornamental value.

Moving

Avoid it: it has a deep taproot and recovers poorly.

Tip: Plant it high and dry, on a bank or in a rock garden, with a layer of gravel around the crown: then it returns every winter. Wet winters are its worst enemy.

Missouri evening primrose: when to prune it?

Pruning months: March.

When: It is hardly pruned. In March, cut off the dead stems, before the new shoots appear.

How:

• Cut dead or damaged stems to just above the ground.
• In March, shorten stems that are too long and bare to about 5–10 cm.
• During summer, remove spent flowers if you want a longer flowering.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

In April–May in a seed tray or pot, barely covered, in a warm, bright spot. It often flowers in the first or second year.

Cuttings

In May–June: take 6–8 cm cuttings from young shoots, remove the lower leaves and insert in sandy compost.

Missouri evening primrose: how does it get through the winter?

Hardy to −25 °C.

• Hardy down to about −25 °C; the problem is not the cold but a wet winter, which makes the crown rot.
• Provide excellent drainage and a layer of gravel around the crown; plant preferably on a bank or in a rock garden.
• In a pot: use a very free-draining compost and put the pot under an overhang in winter so it does not get soaked.

Diseases and pests

• Crown rot: The plant yellows and dies in wet winters or on heavy soil. Plant high and dry and improve the soil with coarse sand and grit.
• Slugs: Young shoots nibbled in spring. Collect them in the evening or lay a ring of coarse grit around the plant.
• Poor flowering: In shade or rich soil it flowers sparsely. Give it a sunny spot in poor soil.
• Flowers open for only a day: Each flower opens only briefly; that is normal. The plant keeps producing new buds.

Through the year

• March: Cut back dead stems. Top up the gravel.
• April: Plant or sow.
• May: Plant. Take cuttings if wanted.
• June: First flowers. Enjoy the evenings.
• July: Full flower. Water only in very long dry spells.
• August: Flowering. Remove spent flowers.
• September: Last flowers. Leave the seed capsules.
• October: Resting. Keep the plant dry; check the gravel layer.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The name macrocarpa means ‘large-fruited’ and refers to the big capsules with four wings.
• The same plant is also called Oenothera missouriensis, after the US state of Missouri.
• Its large yellow flowers are visited in the evening by moths such as hawkmoths.