Chrysogonum: Planting, Growing and Care

Description and botany

Chrysogonum, also known as “Golden Knee”, is a perennial groundcover plant belonging to the Asteraceae family, just like daisies, asters or sunflowers. The genus comprises only one species, Chrysogonum virginianum, native to the fresh woodlands of eastern United States. It has given rise to a few varieties and one more compact, widely spread cultivar, ‘André Viette’.

Chrysogonum virginianum, botanical plate, circa 1925

This creeping, stoloniferous perennial plant spreads to form a dense groundcover thanks to its long underground rootstocks. They take root to create a more or less compact vegetative mat, 25-30 cm in height, spreading at least 40-50 cm. Chrysogonum spreads slowly without ever becoming invasive. This carpeting clump, taller than it is wide, is deciduous, disappearing with the cold and reappearing in spring.

The reddish-green aerial stems, short and upright, are pubescent and highly branched. They bear prominent nodes from which the pedicels emerge, their shape reminiscent of a knee, hence the plant’s nickname ‘Golden Knee’.

They develop small deciduous leaves, bright green in colour, opposite, oblong, 3 to 10 cm long. Villous and slightly puckered, with crenate or dentate margins and prominent veins, they resemble those of lemon balm in our gardens.

With its slightly pubescent texture, this foliage serves as a setting for Chrysogonum’s generous flowering. It begins in May and continues uninterrupted until the first frosts. Star-shaped solitary heads emerge from this verdant profusion, in the axils of the upper leaves. They open as pure yellow daisies, 2 to 4 cm in diameter. They consist of a row of 5 broad, rounded florets radiating around a central disc with more or less visible sun-yellow pistils. They have a plicate appearance and are slightly fringed at their tips.

These sun-kissed flowers later produce seeds that self-sow easily, ensuring the plant’s longevity and allowing it to naturalise in the garden.

Chrysogonum flowers and foliage

Species and varieties

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Planting Chrysogonum

Where to Plant It?

A bit slow to establish, Chrysogonum takes about two years to fully fill out, though flowering occurs as early as the first year of cultivation. Over time, it forms small, highly floriferous clumps. Perfectly hardy (down to -23°C), it thrives in most gardens across our regions. Preferring moist soils over arid ground and intolerant of water shortages, it dislikes very dry summers, making cultivation tricky in Mediterranean climates.

As for soil, it adapts to any light, well-draining, humus-bearing, or even peaty soil that retains moisture, especially in summer. Highly adaptable, once well-rooted, it can tolerate temporarily waterlogged or occasionally dry conditions.

In a spot with non-scorching sun or light shade, and cool in summer, it will form clumps that expand over time while remaining easy to control. It can also thrive in deeper shade. Avoid planting it near tree or bush roots, as it dislikes root competition.

Non-invasive, take advantage of its unique groundcover qualities to fill a cool, shaded rockery, a pathway border, a shady slope, the edges of a water feature, to edge a perennial bed, or brighten a lightly shaded woodland edge. It’s an excellent plant for beautifying the north side of a house. It’s also useful for covering the base of a rose bush.

When to Plant It?

Planting takes place in spring (February to April) or autumn (September to November), avoiding frost and extreme heat.

How to Plant It?

Space young plants about 40 cm apart and allow for 5 plants per m² to create a dense groundcover. Add gravel to improve drainage if needed.

• Dig a hole 2 to 3 times wider than the root ball
• Place the plant in the centre of the hole
• Fill with a mix of good-quality compost, garden soil, and a handful of compost
• Firm the soil
• Water regularly to encourage establishment

→ Check out our tips for planting perennials successfully!

Chrysogonum virginianum and Stachys thunbergii (© Peganum)

Maintenance and Care

Hardy and vigorous, the Chrysogonum virginianum requires almost no care once well established.

It prefers a soil that does not dry out too much in summer. It needs sufficient moisture at the base, especially in summer or if rainfall is scarce. Ensure regular watering during the first year of growth, then 1 to 2 times a week during hot spells. It can tolerate temporary drought once properly rooted. A mulch (straw, leaves, etc.) spread over the stump will help reduce evaporation.

If your soil is poor, adding compost at its base in spring will be beneficial.

Remove faded flowers to encourage new growth.

In autumn or late winter, pull out excess leafy stolons to control the plant’s spread. Divide clumps every 2-3 years to keep them strong and healthy.

The Chrysogonum virginianum is never diseased and is resistant to parasitic attacks. However, in spring, follow our advice to protect its young foliage from slugs and snails.

Propagation

Chrysogonum spreads easily through underground rootstocks and self-sowing. If you’ve harvested its seeds at ripeness, you can sow them in buckets or trays in spring, placing them in a cold frame. Dividing clumps in spring before flowering or in early autumn is simpler to achieve. To propagate, you can also simply separate runners and replant them immediately in the garden in moist soil.

Division

• Lift a section of the stump with a garden fork
• Divide it into several sections, each with roots and the beginnings of leaves
• Replant straight away in open ground and monitor watering to ensure successful establishment

Pair

The Chrysogonum virginianum is an attractive groundcover plant that brightens up cool, shady areas of the garden with its long-lasting, sunny flowering. It pairs well with perennials that thrive in fresh soil and partial shade. It fits perfectly in a naturalistic garden or water garden.

It thrives in moist but not waterlogged soil along the edges of ponds or water features, alongside the yellow-orange flowering Ligularia dentata ‘Dark Beauty’ and the golden Carex elata ‘Aurea’, creating a luminous composition.

Arums, hostas, meadowsweets, Virginia bluebells, and hardy geraniums such as hardy geranium ‘Bob’s Blunder’ and hardy geranium ‘Gravetye’ will also make excellent companions.

A planting combination in moist soil featuring Chrysogonum, Tradescantia, Ligularia dentata, and striking hostas

It can also accompany summer-flowering plants in non-scorching sunlight, provided the soil remains moist. It works well to fill gaps in perennial borders alongside Knautia, masterworts, or blue Phlox such as Phlox divaricata ‘Chattahoochee’. It can also be used to underplant roses alongside other groundcover perennials, such as Heucherellas like Heucherella ‘Stoplight’ with its lime-green to yellow foliage and creeping Bugles.

→ Discover more planting ideas with Chrysogonum with Virginie’s expert advice!