American alumroot

American alumroot: how do you recognise it?

Habit

Rounded, compact clump about 30 cm tall and 45 cm wide; the flower stems reach about 45 cm.

Foliage

Heart-shaped to round, 5–10 cm across, with 5–7 lobes and a toothed edge; marbled green, bronze and silver, almost evergreen.

Flower

Small greenish-white bells with a pink or purple tinge, in loose panicles on thin stems from May to July.

Colour

The foliage is purplish when young, then marbled green with bronze; in winter it turns bronze-brown.

Roots

A woody, creeping rootstock that rises above the soil over the years.

Flowering: May–July · Plants: March–May and September–October · Pruning: March

Why grow it?

• Handsome marbled foliage that stays decorative all year, even in winter.
• Does well in part shade and tolerates drier shade too, where few plants thrive.
• The small bells from May to July are a nectar source for bees.
• A tough, unassuming ground cover: the clump closes up well, suppresses weeds and widens year by year.
• Low maintenance and hardy well below freezing.

American alumroot: where does it grow best?

• Part shade or light shade; in full sun the foliage can scorch or fade. A little morning sun is no problem.
• Humus-rich, well-drained soil: sand, loam or clay, acid to chalky. It hates standing wet.
• Dry to average moisture: it tolerates a dry summer, but not permanently wet soil.
• Sheltered, for example under shrubs and trees with a light canopy, or on the shady side of a wall.
• Space plants 30–40 cm apart; as ground cover 35 cm.

Light

Partial shade and shade

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Dry or normal

Size

0.45 m tall, 0.45 m wide

Hardiness

Hardy (to -35 °C)

Goes well with

• Hosta: Large, leafy plants in the same part shade.
• Barrenwort: Delicate flowers in spring and foliage that is decorative all year.
• Japanese forest grass: A soft, flowing clump next to the sturdy heuchera foliage.
• Hardy geranium: Blue or pink flowers in spring and summer.
• Lady’s mantle: A light, yellow-green edge at the front of the border.

American alumroot: when and how to plant it?

Plant in March–May and September–October.

1. Plant in March–May or 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 with the crown at soil level or just below: no deeper, or it will rot.
4. Leave 30–40 cm between plants.
5. Water thoroughly straight away and keep the soil moist during the first year.
6. Spread a layer of fine bark or leaf mould around the plant, keeping the crown free.

Care

Water

Regularly in dry weather during the first year. After that, water in long dry spells is enough.

Feeding

In spring a thin layer of compost or an organic feed. No more is needed.

Mulching

A layer of leaf mould keeps the soil cool and moist. Keep the crown free.

Re-planting

Because of the woody rootstock the plant rises above the soil after a few years: lift it, replant it deeper and cover the stem with soil.

Flower stems

Cut them off in July if you grow the plant just for its foliage; leave them for the bees.

Tip: Check each spring that the plant has not risen out of the ground: if so, lift it and replant it deeper. That keeps the clump compact and encourages new roots.

American alumroot: when to prune it?

Pruning months: March.

When: In March, cut away tatty or damaged leaves; cut the flower stems once they have finished flowering.

How:

• In March, cut tatty or crumpled leaves just above the crown, before the new leaves come up.
• If you like, cut spent flower stems off at the base in July.
• Remove dead or dried-out leaves regularly to keep the clump healthy.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In spring or September, lift the clump, discard the woody centre and replant the young, rooted pieces deep enough that the leaves just emerge from the soil. Water well.

Seed

The seed is very fine; scatter it on the surface in spring, uncovered. Germination is variable and the seedlings do not always resemble the parent.

American alumroot: how does it get through the winter?

Hardy to −35 °C.

• Fully hardy to about −35 °C: no protection is needed, even in the hardest Belgian winters.
• The foliage largely stays on and takes on warm bronze tones; cut it back only in March.
• After a hard frost the plants may be heaved out of the ground: check in spring and firm them back in.
• In a pot: put it in a sheltered spot and do not let the pot stand in water.

Diseases and pests

• Vine weevil grubs: The fat white grubs eat the roots in autumn and winter; the plant goes limp or topples. Use biological nematodes in August–September when the soil is warm enough.
• Leaf scorch: Brown, dry edges on the leaves in full sun or drought. Move to part shade and water.
• Powdery mildew: White powder on the leaves in a dry summer. Water at the base and cut off affected leaves.
• Slugs: They make holes in the leaves in spring. Pick off slugs or lay a barrier of crushed shells.
• Crown rot: The crown rots in heavy, wet clay. Ensure good drainage and do not plant too deep.

Through the year

• March: Cut away tatty foliage. Plant. Apply compost.
• April: Plant. Mulch. Watch for slugs.
• May: Flowering begins. Water in dry weather.
• June: Flowering. Bees visit the bells.
• July: Flowering ends. Optionally cut off flower stems.
• August: Nematodes against vine weevil grubs. Water in dry weather.
• September: Plant or divide. Nematodes still possible if the soil is warm.
• October: Plant. Spread leaf mould.
• November: The foliage turns bronze-brown.
• December: Dormant. The foliage stays decorative.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The plant is named after Johann Heinrich von Heucher, a German physician and botanist of the 18th century.
• Crossing a heuchera with a foamflower (Tiarella) gives a Heucherella: a plant combining the foliage of one with the flowers of the other.
• In the wild, American alumroot grows in open woods and on rocky slopes in eastern North America.