Blue-stemmed goldenrod

Blue-stemmed goldenrod: how do you recognise it?

Habit

A clump of slender, arching stems, about 70 cm tall and 50 cm wide.

Stems

Purple with a bluish-white, waxy bloom; this gives the plant the name caesia, ‘bluish grey’.

Leaves

Narrowly lance-shaped, smooth and dark green, spaced along the whole stem.

Flowers

Small golden-yellow flower heads in clusters in the leaf axils along the stem, in September–October.

Roots

A short rootstock; the clump widens only slowly.

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

Why grow it?

• Late flowers in September and October, when little else is in bloom in the shade garden.
• One of the few goldenrods for partial shade and shade.
• Nectar and pollen for bees, bumblebees and butterflies at the end of the season.
• Forms a neat clump and does not spread, unlike Canadian goldenrod.
• Graceful, arching stems with a bluish sheen, attractive even out of flower.
• Easy and tough: rarely troubled by disease and needs no staking.

Blue-stemmed goldenrod: where does it grow best?

• Partial or light shade, for example under tall trees or on a woodland edge.
• Sandy or loamy soil, rich in humus, acid to neutral.
• Normally moist: not bone dry, but not boggy either.
• Plant 40–50 cm apart, ideally in groups of three or more.

Light

Partial shade and shade

Soil type

Sand or loam

Acidity

Acid or neutral

Moisture

Normal

Size

0.7 m tall, 0.5 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Ferns: Fresh green foliage as a backdrop for the yellow garlands in shade.
• Japanese anemone: Flowers at the same time, in white or pink, and also likes partial shade.
• Wood aster: Small white or pale blue starry flowers, also for partial shade.
• Sedge: An evergreen, fine, grassy accent in shade.
• Hosta: Large leaves at the base as a contrast with the slender stems.

Blue-stemmed goldenrod: when and how to plant it?

Plant in March–May and September–October.

1. Plant from March to May or in September–October, when the soil is neither frozen nor waterlogged.
2. Loosen the soil and work in some leaf mould or compost.
3. Dig a hole well larger than the pot and set the plant at the same depth as it was in its pot.
4. Leave 40–50 cm between plants.
5. Firm the soil and water in thoroughly straight away.
6. Spread a layer of leaf mould or fine wood chips around the base.

Care

Watering

Water in dry spells during the first year; after that, only during long droughts.

Feeding

Needs little: some leaf mould in spring is enough.

Mulching

A layer of leaf mould or fine wood chips, like a woodland floor, keeps the soil loose and moist.

Faded flowers

Leave them until late winter; cut them off sooner if you do not want seedlings.

Dividing

Every 4–5 years, when the centre of the clump becomes bare or flowers less.

Tip: Plant it on a woodland edge or under tall trees where some light filters through in autumn: that is where the yellow garlands glow best.

Blue-stemmed goldenrod: when to prune it?

Pruning months: March and November.

When: Goldenrod needs hardly any pruning. Cut the old stems down in February–March; if you do not want seedlings, you can also do this in November, straight after flowering.

How:

• In late winter, cut the dead stems back to about 5 cm above the ground.
• To prevent seedlings, cut off the faded stems before the fluffy seed ripens and blows away.
• No other pruning is needed: the stems stay sturdy and need no support.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April or in September, lift the clump and split it into pieces with a few shoots each. Replant straight away.

Seed

Sow ripe seed in autumn in a pot left outside over winter; the cold helps germination.

Cuttings

In May, take young shoots of 5–8 cm from the base and root them in moist cutting compost under plastic.

Blue-stemmed goldenrod: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, to about −30 °C: no protection needed.
• The stems die back in winter; leave them standing until late winter as shelter for insects.
• In a pot: stand it in a sheltered spot and do not let the compost dry out or become sodden.

Diseases and pests

• Powdery mildew: White powder on the leaves in dry late summers. Less common than on many other goldenrods; watering in dry spells helps.
• Rust: Orange-brown pustules on the undersides of the leaves. Remove affected leaves and give the plant an airy spot.
• Slugs: They eat the young shoots in spring. Pick them off in the evening.
• Seedlings: Where it is happy, a few seedlings may appear here and there. Weed them out young or cut the stems after flowering.

Through the year

• March: Cut down old stems. Plant and divide.
• April: Plant. Add leaf mould or mulch. Watch for slugs.
• May: Plant. Take cuttings.
• June: Water during prolonged drought.
• August: Flower buds swell along the stems.
• September: Flowering begins. Plant and divide.
• October: Full flower, busy with bees. Plant.
• November: Collect seed and sow in a pot. Cut faded stems if you wish.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Butterflies

Nectar for butterflies.

Did you know?

• Goldenrod pollen is heavy and sticky and is carried by insects, not by the wind.
• Caesia comes from the Latin caesius, ‘bluish grey’, after the bloomy stems.
• Unlike this species, Canadian goldenrod and giant goldenrod are invasive non-native plants in Belgium, forming large, dense stands on verges and waste ground.