Roscoea: Planting, Growing and Caring for These Exquisite Perennials

Botany

Roscoeas comprise 22 species of tuberous herbaceous perennials native to East Asia, mainly from China, Nepal and India. They grow in scree, meadows and forest edges, between 1,200 and 5,000 metres above sea level, in mountainous regions, particularly the Himalayas. This explains their good hardiness, as Roscoeas can withstand temperatures as low as – 15 to – 20 °C.

Being deciduous, Roscoeas spend the winter underground as tubercles, emerging late in spring, which protects them from the cold! In regions with harsh climates, this protection can be enhanced by placing a thick mulch over the stump, providing additional thermal insulation.

Roscoea belongs to the ginger family, the Zingiberaceae. Most plants in this family are tropical, but Roscoea comes from cool mountainous regions, showing considerable hardiness. This family includes many plants used as spices: turmeric, ginger, cardamom, galangal… as well as ornamental plants such as hedychiums and alpinias.

Roscoea purpurea: Botanical illustration

The Roscoea was named by English botanist James Edward Smith in 1806, in honour of his friend William Roscoe, founder of the Liverpool botanical garden. Roscoe was known for his interest in Zingiberaceae and had a fine collection himself. The species name purpurea alludes to the colour of the flowers.

Roscoeas are not very large plants: they typically measure 30 to 40 cm tall. However, the smallest species, such as Roscoea humeana, do not exceed 20 cm in height, while the tallest, like Roscoea cautleyoides, reach around 60 cm. In the garden, Roscoeas are best placed at the front of borders.

Roscoea forms tuberous roots, resembling those of Dahlias. These allow the plant to store minerals and water, enabling it to overwinter in dormancy underground and thus protect itself from the cold.

Roscoea flowers in summer, between June and September, depending on the variety. The flowers appear above the foliage, at the top of their pseudostems (formed by the rolled bases of the leaves). Their flowers have a complex structure and closely resemble orchid flowers. They measure about 5 cm in diameter and have soft, luminous hues: most often mauve violet or white, but can also be pale yellow (Roscoea cautleyoides) or bright red (Roscoea ‘Red Gurkha’). Their delicate, airy style makes them easy to incorporate into naturalistic partial shade gardens! The decorative parts of the flowers consist of three petals (with an upper petal forming a galea, and two finer petals) and four sterile stamens (staminodia), which resemble petals: two are positioned above, and the other two are fused into a central lower lip. The flower also has one fertile stamen, which carries the pollen.

Roscoea flowers come in beautiful hues depending on the variety! Roscoea purpurea, Roscoea ‘Red Gurkha’, Roscoea ‘Spice Island’ (photo Teresa Grau Ros), and Roscoea cautleyoides

The flower extends into a long floral tube containing nectar. When insects land on the flower to consume the nectar, they touch the fertile stamen, which automatically deposits pollen on their backs. They then carry this to the pistil of another flower, enabling its fertilisation and the development of seeds.

Roscoeas are deciduous: their leaves dry out in autumn and regrow in spring. They start late in spring: the first shoots and leaves only appear around June. This protects the plant from late frosts. It then grows rapidly, sometimes producing flowers as early as June or July.

Roscoea leaves are lanceolate, long and slender, arched. They generally measure between 15 and 25 cm long and are sheathing at the base (the lamina surrounds the stem). The foliar sheaths can be green or coloured: sometimes purple, brown or red depending on the species. The Roscoea ‘Spice Island’, for example, has brown foliar sheaths and dark leaves with reddish undersides, which beautifully highlights the flowering!

After flowering, Roscoea forms capsules containing seeds. These have arils, small fleshy outgrowths consumed by insects, particularly ants. Attracted by the arils they eat, the ants carry the seeds with them, helping the plant to spread.

The foliage of Roscoea purpurea ‘Red Gurkha’, Roscoea auriculata ‘Floriade’ (photos: Leonora Enking) and Roscoea ‘Cinnamon Stick’, with its reddish foliar sheaths

The main varieties of Roscoea

The Most Popular Varieties

Our Favourite Varieties

Other Varieties to Discover

Roscoea purpurea

This is the typical species, the most common in cultivation, which has given rise to different varieties. From June-July it bears violet flowers, 5 cm in diameter, which closely resemble orchid flowers.

• Flowering time August to October
• Height at maturity 40 cm

See the product sheet

Roscoea purpurea Cinnamon Stick

This Roscoea offers flowers in very soft, luminous shades in late summer: pale mauve to rosy white, enhanced by dark, purplish-brown foliar sheaths.

• Flowering time September, October
• Height at maturity 50 cm

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Roscoea purpurea Spice Island

This variety forms cinnamon-brown foliar sheaths and dark green leaves with reddish undersides. At the top of the stems, mauve orchid-like flowers appear in late summer, with a pink floral tube and upper petal, creating a lovely gradient.

• Flowering time September, October
• Height at maturity 60 cm

See the product sheet

 

Roscoea cautleyoides

This species stands out for its yellow flowering, a rare colour among Roscoea! It is particularly useful for brightening up a shady corner of the garden.

• Flowering time August to October
• Height at maturity 30 cm

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Roscoea purpurea Dalai Lama

Roscoea ‘Dalai Lama’ offers a beautiful purple-violet flowering in summer. It has been awarded the Award of Garden Merit by the Royal Horticultural Society (RHS).

• Flowering time August to October
• Height at maturity 40 cm

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Roscoea beesiana

Roscoea beesiana offers a creamy-white, almost yellow flowering, with the lower petals irregularly spotted with violet.

• Flowering time August, September
• Height at maturity 40 cm

See the product sheet

 

Roscoea humeana

This is a small and early Roscoea, which bears intense violet flowers from May to July, resembling orchids. It is a collector's plant, rare in cultivation.

• Flowering time June to August
• Height at maturity 25 cm

See the product sheet

Roscoea beesiana Alba

This variety stands out for its pure white, very luminous flowers.

• Flowering time July to September
• Height at maturity 40 cm

See the product sheet

 

Planting Roscoea

Where to plant?

Plant Roscoea preferably in partial shade, or in non-scorching sun if you live in the northern half of France. It needs shade during the hottest hours but still enjoys bright locations. Under dense, heavy shade, Roscoea may develop a more lax habit and less pronounced colours. If possible, choose a spot sheltered from cold winds.

Roscoea thrives in rich, humus-bearing soils: don’t hesitate to add well-rotted compost at planting time. It also prefers soils that remain cool in summer yet are well-drained. Regarding pH, Roscoea favours acidic soils but will also grow in neutral soil. You can add some heather soil when planting.

As it enjoys well-drained, even stony soils and is naturally found in scree zones, Roscoea will thrive in a cool rockery in shade or partial shade. With its delicate orchid-like flowering, it’s also perfect for shaded naturalistic gardens and Asian-style gardens. It adapts equally well to container planting and can enhance a north- or east-facing terrace, small garden, or balcony.

When to plant?

The best time to plant Roscoea is in spring, around May, once the risk of frost has passed.

How to plant?

In the ground:

1. Once you’ve chosen the location, dig a planting hole, at least 20-30 cm deep. Feel free to dig a wide hole to plant several young plants together.
2. Mix well-rotted compost and coarse sand into the planting soil to enrich the soil and ensure good drainage.
3. Plant the Roscoea tubercles 10-15 cm deep.
4. Cover with soil and firm gently.
5. Water thoroughly.

In pots:

1. Choose a pot at least 30 cm deep. Ensure it has drainage holes at the base to allow excess water to escape.
2. Add a drainage layer of clay pebbles or gravel.
3. Then fill with a mix of potting compost, garden soil, and coarse sand.
4. Plant the tubercles so they’re buried under 10-15 cm of substrate.
5. Cover them with compost.
6. Water.
7. Place the pot in partial shade.

→ Learn more about growing Roscoea in pots in our advice sheet!

Roscoea purpurea

Maintenance

Native to monsoon regions, Roscoeas require moisture in summer and relatively dry conditions in winter. The ideal is to keep the soil cool in spring and summer: remember to water regularly when rainfall is insufficient. Once the Roscoea has flowered, you can reduce watering, then stop it completely as soon as the plant enters dormancy. Don’t hesitate to apply a layer of mulch at its base to preserve soil moisture for longer.

In most French regions, Roscoea can remain in the ground over winter, as it tolerates temperatures as low as –15 to –20°C. However, if you live in an area with particularly harsh winters (montane or semi-continental climate), you can protect the Roscoea from the cold by covering the stump in autumn with a thick mulch of dead leaves or bark. If grown in pots, it’s easy to move them into an unheated greenhouse or any frost-free shelter. Similarly, planting the tubercles deep (around 15 cm below the surface) helps shield the Roscoea from frost.

Feel free to add well-rotted compost around the base of the Roscoea in spring to enrich the soil and encourage flowering.

You can remove spent flowers as you notice them, both for aesthetics and to encourage the plant to produce new blooms.

Watch out for snails and slugs in spring, as they enjoy nibbling on young leaves and shoots. You can protect your young plants with slug repellent or create a slug trap. For more tips, check out our guide “Slugs: 7 Effective and Natural Ways to Control Them”. Vine weevils may also target Roscoeas.

Propagation

Roscoeas can be propagated by sowing fresh seeds or by dividing clumps. Division is quicker and easier to succeed with than sowing.

Sowing

Sowing Roscoea is carried out in late summer, in August or September, using fresh seeds (harvested shortly before).

1. Prepare pots with a fine, well-draining substrate, ideally a special sowing compost, then lightly firm and level the surface.
2. Sow the seeds by scattering them on the surface.
3. Cover them with a very thin layer of compost.
4. Water gently, using a fine spray.
5. Place the pots in a cold frame, in a bright spot without direct sunlight, and ensure the substrate remains slightly moist until germination.

Once the seedlings reach a size that allows handling, you can repot them into individual pots. Patience will then be required: Roscoeas grown from sowing generally take 3 to 4 years before they start to flower.

Dividing clumps

Division is the ideal technique if you have large, well-established Roscoea plants. It is carried out in spring. You can divide your Roscoeas every 3 to 4 years.

1. Choose a large Roscoea clump, then carefully dig it up, making sure to dig wide enough to avoid damaging the roots.
2. Remove any excess soil if necessary, then divide the clump into several sections, ensuring each has roots attached.
3. Replant, either in the ground or in pots, burying the tubercles about 15 cm deep.
4. Water generously.

Association

With its generous foliage and original flowering, Roscoea easily finds its place in an exotic-style garden. Pair it with colourful foliage in warm tones, such as Phormium ‘Pink Panther’, Colocasia ‘Black Magic’, Canna ‘Durban’ or Cordyline ‘Southern Splendour’. Opt for plants with striking, very large leaves: incorporate bananas, palms, Tetrapanax, Gunnera, Fatsia… Their lush vegetation will create a true jungle atmosphere! For flowering companions, consider crocosmias, kniphofias, Belamcanda chinensis, cannas… Alongside these, plant a Hedychium gardnerianum to enjoy its highly original flowering!

Exotic atmosphere with Colocasia ‘Black Magic’ (photo J. Rebel), Roscoea purpurea ‘Red Gurkha’ (photo Leonora Enking), Crocosmia ‘Lucifer’ (photo Vicky Brock), Cordyline australis ‘Southern Splendour’ and Hedychium gardnerianum (photo J.J. Harrison)

The orchid-shaped flowers of Roscoea are also perfect in naturalistic-style gardens. Their light and delicate style fits in wonderfully! For companions, consider the airy blooms of willowherbs, masterworts, stem-clasping persicarias, astilbes, Veronicastrums and Japanese anemones. You could also include garden orchids: discover for example the superb Calanthe triplicata, which offers small, very refined flowers with pure white petals!

Roscoeas can easily be incorporated into a cool, shady rockery, alongside saxifrages, dead-nettles, corydalis and foamflowers. Also consider ferns such as the Asian species Coniogramme emeiensis, with its very graphic fronds, and Hart’s Tongue Fern, which forms clumps of beautiful, long, upright, evergreen green fronds.

Native to East Asia, Roscoeas will find their place in a zen garden of Asian style, alongside Japanese maples, Hakonechloa macra, hostas and bamboos. This will allow you to create a very soothing atmosphere, conducive to meditation!

A naturalistic garden with Epilobium angustifolium, Roscoea cautleoides (photo Andy king50), Geranium riversleaianum ‘Mavis Simpson’, Persicaria amplexicaulis ‘Firetail’, Astrantia major ‘Ruby Star’ and Calanthe triplicata (photo Kuo-Chu Yueh)

→ Discover more pairing ideas with Roscoea in our advice sheet!