The Boykinia: planting, cultivating and maintaining

botany

Boykinia comprises 10 species of herbaceous, rhizomatous perennial plants, primarily native to the United States, and more rarely to Japan. They mainly grow in fresh woodlands, in crevices and rockeries, along stream banks, predominantly in mountainous regions, and occasionally in lowland areas.

Boykinia plants are still relatively obscure and little-known, rarely found in gardens. However, they possess beautiful ornamental qualities, making them ideal for enhancing shady rockeries, and require minimal attention once established. Boykinia are fully hardy, capable of withstanding temperatures as low as -15 °C, or even -20 °C.

Boykinia belongs to the saxifrage family, Saxifragaceae, which includes around 600 species. This family also features other ornamental plants such as bergenias, astilbes, heucheras, rodgersias, and tellimas. These are primarily herbaceous shade-loving perennials, with palmate foliage and five-petaled flowers grouped into compound inflorescences.

The flowers of Boykinia richardsonii, Boykinia occidentalis, Boykinia major, and Boykinia lycoctonifolia (photos: Denali National Park and Preserve / Walter Siegmund / Tom Hilton / Qwert1234)

Boykinia form basal rosettes and spread slowly via underground rhizomes, without becoming invasive. When in flower, they typically reach heights of 30 cm to 70 cm, occasionally up to 1 m.

In early summer (June-July), and in April-May for Boykinia jamesii, Boykinia unfurl above their foliage panicles of flowers. These panicles are borne on upright flowering stems, which are green or reddish in colour. Boykinia produce small, single flowers measuring about 1 cm in diameter (up to 2 cm for Boykinia jamesii). They consist of five white petals, five green sepals, five stamens (male reproductive organs, carrying pollen), and two styles (female reproductive organs, receiving pollen). The flowers are pure white, sometimes pink. The petals are white and very faintly veined with pink in Boykinia richardsonii. The centre of the flowers (between the petals) is yellow or green.

Their inflorescences are admired for their delicate and elegant appearance, reminiscent of saxifrages or gypsophilas. Boykinia are ideal for bringing brightness to shady corners of the garden! Moreover, they have a very natural style and will easily find their place alongside other light and delicate blooms to create a true woodland atmosphere.

Boykinia jamesii stands out for its bright pink flowers, with larger and more widely spaced petals than other species. Additionally, they are grouped into dense, narrow clusters, while the inflorescences of other Boykinia are much lighter and airier. As for Boykinia rotundifolia, it is distinguished by its tubular flowers, with a swollen calyx, similar to Silene vulgaris.

Like many Saxifragaceae, Boykinia form rosettes of leaves, close to the ground. The flowering stem also bears a few leaves (cauline leaves). The leaves are reniform or cordate, with dentate leaf margins. The basal leaves have long petioles, while the cauline leaves are sessile or borne on short petioles. The leaf veins are palmate (radiating from the base in a fan-like arrangement). The leaves are medium to dark green, perfectly complementing the white flowers. The different species have fairly similar leaves, varying in their degree of lobing. Those of Boykinia rotundifolia are particularly rounded, while those of Boykinia aconitifolia resemble the foliage of aconites. Boykinia foliage is deciduous.

After flowering, Boykinia produce capsules (dry fruits that open at maturity) containing black, ellipsoid seeds. These seeds can be harvested for sowing.

The foliage of Boykinia lycoctonifolia, Boykinia aconitifolia, and Boykinia rotundifolia (photos: Qwert1234 / Salicyna / Anthony Valois – National Park Service)

The main varieties of Boykinia

The Most Popular Varieties

Boykinia major

Boykinia major is a beautiful perennial native to the United States, forming rosettes of leaves and bearing panicles of white flowers in early summer, reaching 70-80 cm in height.

• Flowering time August
• Height at maturity 70 cm

See the product sheet

Boykinia occidentalis

This is a slightly smaller species than Boykinia major. Boykinia occidentalis produces panicles of small white flowers with delicate petals.

• Flowering time February
• Height at maturity 40 cm

See the product sheet

Boykinia aconitifolia

This Boykinia offers panicles of white flowers in early summer, light and airy. It also bears beautiful leaves resembling those of aconites.

• Flowering time July, August
• Height at maturity 60 cm

See the product sheet

Planting Boykinia

Where to Plant?

Boykinia are shade-loving plants that thrive in cool, rich, humus-bearing soil. They prefer woodland-like conditions and can even tolerate heavy soils. They favour slightly acidic soils. If your soil is alkaline, you can plant Boykinia in pots or create a planting pocket with a rich, acidic, and well-draining substrate.

Boykinia are perfect for cool, shaded rockeries. They also work well in woodland gardens or along pond edges. You can even create a miniature rockery in a trough by pairing Boykinia with saxifrages, houseleeks, Lewisia, and more. Boykinia can also be planted on a stone wall, provided there is enough space between the stones to create small pockets of substrate and to incorporate a mix of compost, coarse sand, and well-rotted compost. Boykinia jamesii is particularly suited to wall planting, as it requires very little substrate and can settle into the cracks between stones.

Check out our guide “Creating a Rockery: Our Tips for Success”.

When to Plant?

You can plant Boykinia in spring, around April, or in autumn, during September-October. The key is to avoid periods of frost or extreme heat.

How to Plant?

Since Boykinia is a small, delicate, and understated plant, we recommend planting several together for a more striking effect. Space them about 40 cm apart.

1. Start by digging a planting hole, roughly twice the size of the root ball, or find a spot between stones in a rockery or wall.
2. Add a mix of compost, well-rotted compost, and coarse sand.
3. Remove the Boykinia from its pot and plant it.
4. Fill in around the plant with substrate and gently firm it down.
5. Water thoroughly.

Continue to water regularly in the weeks following planting.

Boykinia elata (photo USFWS – Pacific Region)

Maintenance

Once planted, the Boykinia requires very little attention. It is resistant to diseases and parasitic pests. Water it during dry spells to keep the soil slightly moist. If your water is hard, use rainwater if possible. You may add some well-rotted compost to enrich the soil and support flowering.

You can remove faded flowers for aesthetic reasons and to relieve the plant, unless you wish to harvest the seeds for sowing.

Multiplication

Boykinia can be propagated by sowing or division of clumps.

Sowing

We recommend placing the seeds in the refrigerator for a few weeks before sowing to break their dormancy. Sow them under cover in late winter or early spring.

1. Prepare a pot with special sowing compost.
2. Lightly firm and level the surface.
3. Sow the seeds on the surface.
4. Cover them with a thin layer of sand or compost and gently firm.
5. Water with a fine spray.

Transplant the seedlings into individual pots once they reach 5 cm in height or are large enough to handle safely.

Division of Clumps

Boykinia spreads gradually via its rootstocks. If you have a well-developed clump, sufficiently large, that has been in place for several years, you can divide it.

1. Dig widely to avoid damaging the Boykinia and its roots.
2. Separate it carefully, ensuring each new young plant has roots.
3. Replant in a new location after preparing the soil, or in a pot.
4. Water generously.

Association

The Boykinia will easily find its place in a cool, shaded rockery. It is perfect for accompanying saxifrages. Incorporate plants with decorative foliage, such as Carex morrowii ‘Ice Dance’, ophiopogon, hostas… Also consider ferns, such as Cyrtomium falcatum, Polypodium vulgare, or Asplenium scolopendrium. Enjoy the bright and delicate flowering of Chiastophyllum oppositifolium, nicknamed Golden Drop.

The Boykinia is perfect for a shaded rockery. Saxifraga arendsii ‘Pixie White’, Boykinia occidentalis (photo Walter Siegmund), Lamium maculatum ‘Roseum’, Chiastophyllum oppositifolium, Asplenium scolopendrium (photo Florian Grossir), and Coniogramme emeiensis

You can also create a miniature rockery in a trough, with small alpine perennials. Incorporate plants whose foliage forms small carpets, cushions, or rosettes close to the soil, such as houseleeks, saxifrages, Lewisia, and Azorella. You will achieve a kind of miniature garden, very decorative and easy to install on a terrace or near the house to enjoy it to the fullest.

You can compose a wild and natural shade garden with the Boykinia. It can find its place at the front of a border or along a path, near ferns, hostas, heucheras, and tiarellas. Also consider Geranium nodosum and the very delicate flowering of Thalictrums.