Rue-leaved saxifrage

How to recognise it

Habit

Annual of 3–15 cm, with an upright stem that is often branched from the base. The whole plant is glandular-hairy and sticky.

Leaf

Small leaves, usually three-lobed or three-toothed at the tip, like three little fingers. The lower ones form a tiny rosette and are often tinged red.

Flower

White flowers a few millimetres across with five petals, on long stalks; from March to May.

Fruit/Seed

Small capsule full of dust-fine seeds, spread by wind and rain.

Stem

Thin, red to reddish brown, with sticky glandular hairs.

Confusion with

Common whitlowgrass flowers just as early in the same places, but has a rosette of undivided leaves, deeply split petals and small flat pods. Little mouse-ear has slightly notched petals and opposite, undivided leaves.

Flowering: March–May

Why grow it?

• One of the earliest flowers on walls and gravel, when little else is in bloom.
• The tiny flowers are visited by small flies, small bees and hoverflies, although the plant often pollinates itself too.
• A typical species of stony habitats in towns: walls, gravel paths, cemeteries and roofs.
• Perfect on a green roof, a wall top, a rock garden or in the joints of a patio you do not weed.
• Its sticky glandular hairs sometimes trap minute insects: a lovely detail to look at with a hand lens.
• Once present it self-seeds every year without any maintenance.

Rue-leaved saxifrage: where does it grow best?

• In the wild: old walls with lime mortar, dune grassland, chalk and limestone grassland, gravel and railway ballast, cemeteries and pavement cracks in towns.
• Full sun; at least a spot that gets plenty of light in spring.
• Dry, poor, limy or sandy soil with little competition; it needs small bare patches to germinate.
• In the garden: a wall top, rock garden, gravel garden, sedum roof or patio with open joints.

Goes well with

• Biting stonecrop: Yellow flowers in June in the same dry, stony spot.
• Common whitlowgrass: Flowers at the same time and shares the same open patches of gravel and sand.
• Wall-rue: A small fern of old limy walls.
• Wild thyme: A fragrant, low flower for bees on a poor wall top or in a rock garden.

Rue-leaved saxifrage: when and how to plant it?

1. Buy seed from a nursery or seed supplier for native plants, or collect a few ripe capsules in a friend’s garden. Never dig plants up from the wild.
2. Sow in September–October: the seed germinates in autumn and the plant has to overwinter to flower in spring.
3. Scatter the dust-fine seed thinly on gravel, sand or in wall joints and do not cover it: it germinates in the light.
4. If you like, mix the seed with a little fine sand so you can spread it evenly.
5. Do not water, except in a very dry autumn; after that it looks after itself.
6. Keep the spot open: no mulch, no compost, no weed burner and no pressure washer.

Care

Water

Not needed: the plant lives during the wet months and has withered before the summer drought begins.

Feeding

Never. Fertiliser makes grass and moss grow, which crowd it out.

Weeding

Keep grass and moss a little short around the plants, but leave bare patches open.

Letting it seed

Leave the withered plants until the end of June so that all the seed is released.

Walls

Do not completely repoint old walls or clean them with a pressure washer: that is where it lives.

Tip: Sow rue-leaved saxifrage in autumn on a wall top or in a gravel bed and leave the spot alone in spring: if you do not weed until July, it will come back every year.

Pruning and mowing

When: Not needed. Simply leave the withered plants until the seed has dropped, usually at the end of June.

How:

• Do not cut or mow until the plants have turned completely brown in June.
• After that you can sweep them away or let them rot down: the seed has already fallen.
• Do not mow a gravel garden or sedum roof with rue-leaved saxifrage in spring.

Pruning calendar and basic rules

Propagation

Seed

Self-seeds. To sow it yourself: in September–October on an open, poor spot; the seed germinates in autumn.

Rue-leaved saxifrage: how does it get through the winter?

Hardy to −20 °C.

• Overwinters as a small rosette a few centimetres across, often reddish.
• Very hardy: the rosette tolerates frost down to about −20 °C and snow without any trouble.
• The seed in the soil survives every winter.

Diseases and pests

• Crowding out: Moss, grass and larger plants take over the bare patches. Keep the spot poor and open.
• Over-tidiness: Weeding, flame weeding and pressure washing between February and June destroy the plants before they set seed.
• Soil too rich: On compost or potting soil it grows weak and gets overgrown. Choose sand, gravel or lime rubble.
• Slugs: They may nibble rosettes in a wet winter; rarely a problem on dry walls.

Through the year

• January: Tiny rosettes on walls and gravel; frost is no problem.
• February: The first plants start to grow up. Do not weed.
• March: Flowering begins. Do not pressure wash or flame weed.
• April: Full flower: white flowers on red stalks.
• May: Last flowers; the capsules ripen.
• June: The plants wither and scatter their seed.
• September: Sow on a wall top, gravel or a sedum roof.
• October: New seedlings appear.
• November: The rosettes grow slowly. Keep the spot open.

Did you know?

• The scientific name ‘tridactylites’ means ‘three-fingered’ and refers to the three-lobed leaves.
• Saxifraga means ‘stone-breaker’: saxifrages often grow in cracks in rocks and walls.
• It is a winter annual: it completes its whole life, from germination to seed, in the cool, wet half of the year and so avoids the summer drought.