Rodgersia, once relegated to specialty nurseries and fine garden landscaping, is more widely available for the home garden. This large, showy, flowering perennial has it all, from striking color-changing pinnate or palmate, basal leaves, to towering spikes sporting white, creamy white, and pink flowers in spring and summer.
I. Appearance and Characteristics
Rodgersia is a genus of flowering plants in the Saxifragaceae family. Rodgersia are herbaceous perennials originating from east Asia.
The genus was designated by the American taxonomist, A.Gray, in 1885, who named it after the US Admiral, John Rodgers, commander of the expedition in which R. podophylla was discovered in the 1850s. By 1871, R. podophylla was present in the United States and was flowering in the Imperial Botanical Garden at Saint Petersburg and in 1878, seed brought back to a British nursery, Veitch & Sons, produced flowering plants.
Rodgersia aesculifolia was discovered by Father Armand David in 1869.
Rodgersia pinnata, was also discovered by Abbé David, in China’s Yunnan province, in 1883. It first flowered in the UK in 1902. R. sambucifolia was discovered by Ernest Wilson 1904 in Yalung, China.
Rodgersia nepalensis was not identified until in 1966 in the UK from a collection by Peter Schilling who made a second collection of seeds of this species . There are distinct differences between the plants raised from these two collections whose numbers are EMAK 713/901 and ED2879.
Rodgersia henrici which was initially thought to be an astilbe was collected by Prince Henri d’Orleans in 1895 but this has recently been reduced to a variety of R. aesculifolia.
In older literature there is mention of R. purdomii named after William Purdom who collected it in China in around 1910. The herbarium specimen of a plant raised from that seed, at Kew, identifies it as R. aesculifolia.
Rodgersia podophylla is native to the island of Honshū in Japan and to Korea. All the other species are found in China, Tibet, and Nepal. The geographical ranges of all but R. nepalensis overlap each other.
In their native habitats they grow by streams and in shady moist woodland. In cultivation they thrive in soil that never dries out but is not waterlogged. They will grow in sun under these conditions in good humus rich soil but they are susceptible to sun- and wind-scorch. They are hardy down to Zone 5 but their new growths in the spring can be damaged by late frosts.
The thick rhizomes spread just under surface of the soil. Three of the species are clump forming, whereas R. nepalensis and some forms of R. podophylla can cover large areas quite quickly once they are established.
The strong leaf stems grow to an average height of about one metre but this depends on the variety and growing conditions. The spread of the compound leaves, especially of R. podophylla, can also be up to one metre making them architectural plants in cultivation. The flowering stems rise above the foliage and the panicles of flowers, although lacking true petals, are spectacular and colourful being white, cream, pink or red except in R. nepalensis which are greeny yellow.
The leaves of many varieties are attractive in the Spring when, grown in good light, they have a bronze or copper hue. This is especially beautiful in the Purdomi group of R. aesculifolia which keep a metallic sheen into early summer. In the autumn(fall), the leaves turn attractive shades of coppery-brown. The seed heads are also attractive, those of many R. pinnata are claret coloured which deepens as winter progresses.
II. Species
Rodgersia podophylla
The leaves of R. podophylla, Gray (diploid 2n=30) are palmate. The individual leaflets, from 5 to 7 in number, have between 3 and 5 drip tips at their angular apices. The leaflets resemble a duck’s webbed foot and this is sufficient to identify R. podophylla from all the other species. There are two forms of R. podophylla, one which has tough leathery leaves which are often bronze in the spring and autumn, and a thinner leaved form which remains a light green colour. R. podophylla is often very shy at flowering, but can cover large areas by means of its spreading rhizomes. The flowers are white, the sepals ageing to green as do the ovaries.
Rodgersia aesculifolia
In R. aesculifolia, Batalin (tetraploid 2n=60″) the leaves are symmetrically palmate radiating from a central point most often without petioles.They are obvate with acute apices and coarsely serrated. Recently, R. aesculifolia (chestnut-leaved) has been divided into three distinct taxa.
- White flowered
This has small flowers, 2 – 8mm in diameter. The green, white or yellowish buds open to white flowers that go green with age. It has green leaves throughout the growing season and airy inflorescences with curled flower clusters.
- Purdomii taxon
This also has small flowers 2 – 8mm in diameter but the flower buds are pink opening to sepals tinged or tipped pink turning white, the flowers ageing green. The young leaves are copper or bronze in colour and the older leaves retain a metallic shean. The inflorescences have an airy appearance as in taxon 1.
- Henrici taxon
This has large flowers 8 – 18mm in diameter, a major difference with the other two taxa. The bright pink sepals and ovaries get progressively deeper in colour as they age and remain claret-coloured through autumn. The inflorescences have nothing “airy” about them but are solid-looking, broad based with flower clusters that have almost flat tops with their undersides clearly visible when viewed from the side. They form tiers as in a multiple wedding cake and the flowers are closely packed along the pedicels. The texture of the leaf surface of var. henrici is firm and there is no tendency to deflect downwards from the mid-vein or at the apex, as in the soft-textured var. aesculifolia.
All the veins in var. henrici are sunken, giving the top surface of the leaflets a quilted effect and on the underside, all the veins are prominent. The leaflets of var.aesculifolia have an almost smooth upper surface and only the main veins are prominent on the underside. The normal number of leaflets for var. henrici is 7 – 9 ; for var. aesculifolia it is 6 – 7.Pan (1994) provides a key that separates R.aesculifolia var. aesculifolia from var. henrici. This key states that var. henrici has more glandular hairs on the ventral surface of its sepals than var. aesculifolia and that the arcuate (curved) sepal veins meet at the tips whereas they do not in var. aesculifolia .
From a gardener’s point of view, the general differences in the non-microscopic features of the plants are sufficiently diagnostic.
Rodgersia sambucifolia
Rodgersia sambucifolia, Hemsley (tetraploid 2n=60) The leaves are pinnate and remain green throughout their life. The number of pairs of leaflets varies with the age of the plant and habitat. It is the smallest, in stature, of all of the species having foliage and flower spikes around 500mm tall. The small white flowers rapidly age to browny green. The two varieties established by Pan are distinguished by microscopic features. (Sambucifolia; having leaves like Sambucus, the Elder tree)
Rodgersia pinnata
Rodgersia pinnata, Franchet (tetraploid 2n=60) has the most diverse leaf form of any of the Rodgersia and this leads to mis-identification and mis-labelling in horticulture. Rarely are the leaflets arranged in true pinnate form with evenly spaced leaflets. They vary from pseudo-pinnate, when the leaflets can be bunched 2 to 5 at the petiole and 3 at the apex with varying numbers of pairs of leaflets between with varying lengths of rachis, to plants where the rachis is so compressed as to need very close inspection to ascertain that it is not palmate.
The size of the individual ovate-lanceolate leaflets ranges from 20mm long x 10mm wide to double those measurements depending on variety and growing conditions. The height of the leaves may exceed one metre and that of the inflorescence, one and a half metres. The flowers can be white, palest pink to deep claret colour and the subsequent seeds heads range from green through to deep mahogany. There are many cultivars, R. pinnata is very variable in all its aspects and readily hybridized with both R. podophylla and R. aesculifolia. As with R. sambucifolia, the two varieties established by Pan are distinguished by microscopic features.
Rodgersia nepalensis
Rodgersia nepalensis, T.A.Cope ex Cullen has a truly pinnate leaf, blue-green in EMAK 713, yellowy-green in ED2879. The individual leaflets are about 15mm long and 5mm wide with markedly serrated edges, tipped red brown in EMAK, yellow in ED. The sepals of EMAK are pale green, those of ED pale yellow. The flower colour distinguishes R.nepalensis from all other Rodgersia
III. How to Grow and Care
Sunlight
To get the most from your rodgersia, provide the light recommended for your variety. Different types grow from full sun exposure of six hours daily to nearly full shade of two to six hours daily. Varieties grown in full sun require soil that stays consistently moist.
The amount of light received impacts leaf color which often emerges from bronze in spring, changing to green in summer and turning brilliant shades of red or yellow in autumn.
Temperature and Humidity
Rodgersia is a plant best suited to temperate climates with cooler summers. While temperatures as high as 105°F can be tolerated, plants acclimate better to temperatures between 65°F and 80°F.
This perennial dies back in autumn when temperatures start to drop but roots are hardy to 15°F. In areas with extremely cold winters, protect roots with a layer of mulch. Choosing a location sheltered from strong, drying winter winds helps prevent plant loss.
Watering
Water regularly when first transplanting into the garden. These plants will not thrive without consistently moist soil but, when grown in the correct location, supplemental irrigation is needed only during periods of hot, dry weather. A spot protected from drying winds improves air and soil moisture. Add a layer of mulch to keep plants looking their best until frost.
Soil
Rodgersia are moisture-loving plants found naturally in bogs and wet environments. They adapt to soil type from clay to sand but fertile loam encourages good health and performance. Soil pH from slightly acidic to slightly alkaline is adequate for growing rodgersia.
Fertilizing
Rodgersia benefits from the application of a general-purpose fertilizer in spring when new growth begins. An NPK 10-10-10 helps promote the spread of new plants from the rhizome.
Pruning
In temperate zones remove foliage after dieback in autumn. The flower spikes go on to produce red berries and can be left for autumn interest but should be cut to the ground in late winter or when they turn brown.
Propagation
Rodgersia is propagated through division. These are not long-lived plants but they do have a well-behaved spread and attractive clumping habit. Keep them looking good by dividing mature plants every three years in early spring.
Large clumps can be split and replanted right away. Use a shovel or garden trowel to dig up a clump. Split it into two pieces with a saw or sharp knife. Each section should have a good root system. Set plants at the same level as in their original location.
Smaller divisions have a better chance of survival if potted up and kept in a cold frame or greenhouse overwinter.
How to Grow From Seed
While starting with seed is another way to increase your collection, rodgersia seedlings require some babying. Plants can take as long as three years to reach maturity with full color and bloom. If you have a specific plant, you can let flowers go to seed to collect in autumn and start the following spring. Seeds of cultivars may not produce a plant identical to the parent. Saved seed of some varieties also requires a cold stratification of 60 days.
Seeds germinate anywhere from two weeks to two months depending on species and cultivar. Grow seedlings out in pots for one year before transplanting to an outdoor location. Seeds sown in spring can be left in a cold frame or unheated greenhouse to stratify naturally. Or you can refrigerate them in damp moss or a damp paper towel for two months.
Sow seeds 1/4 inch deep in quality potting soil, and cover lightly. Place in a location with bright, indirect light and keep them evenly moist. Expose seedlings gradually to more light.
Potting and Repotting
Most rodgeria are large plants with a spreading rhizome better suited to growing in the ground. To grow it in a pot, choose a smaller variety and a large container. Leaf and flower size will likely be smaller.
Overwintering
No special care is needed for rodgersia which dies back naturally in autumn. In climates with winter temperatures that drop below 15°F, add a 3-inch layer of mulch to protect roots.
Pests and Diseases
Common Pests & Plant Diseases
Other than snails and slugs which are attracted to the large leaves, rodgersia are not vulnerable to pests or disease.
Common Problems
- Failure to Bloom
Plants that fail to bloom are stressed which is almost always caused by a cultural problem. Review the light, soil, and moisture requirements of your variety and make corrections where necessary.
- Wilt
Rodgersia wilts, dries up and turns brown if soil is allowed to dry out. Grow it in a garden location where soil stays consistently moist and provides shade for at least part of the day.
Foliage Discoloration
Finding the right mix of sun and shade can be a challenge and depends on the type of rodgersia you choose. Too much sun causes plants to take on a straggly, unkempt look and can cause discoloration on foliage. In areas with late spring frosts, early varieties can also suffer frost damage.
III. Uses and Benefits
Adaptable to shady areas, rodgeria works well as a landscaping ground cover, in woodland gardens, around water gardens and streambeds, and makes a bold statement at the back of flowerbeds.
