Corydalis : From Obscurity to the Height of Fashion

Table of Contents and IntroductionAfrican Violets: the Doyen of House PlantsAgapanthusAlstroemeriasAmerican SagebrushesAmerican WildflowersAndean Nymph - a pink mimulusAquilegias (Columbines)AuriculasAustralian AnnualsBellis Perennis (Daisies)Black-Eyed SusanBlue African LiliesBreeding DelphiniumsBreeding Fuchsias: Part 1: From SeedBreeding Fuchsias: Part 2: HybridisationBromeliads from SeedButterflies in Soy SauceCacti RaisingCampanulasChilean Bell FlowerChilly Treatment for Peruvian LiliesCollecting SeedConserving Annuals and BiennialsCosmosCucumbersCycads: Living FossilsCyclamen for IndoorsDahlias from SeedDamping OffErythroniumsF1 Hybrid - What Is it?F2 and Open Pollinated VarietiesFrom Obscurity to the Height of FashionGentiansGeraniumsGermination to Pricking OutGolden Impatiens - The StoryGrowing Alpines From Seed: Part 1Growing Alpines From Seed: Part 2Growing Bananas From SeedGrowing Cyclamen From SeedGrowing Eucalyptus From SeedGrowing Ferns from SporesGrowing Foxgloves From SeedGrowing Fritillarias From SeedGrowing From Seed: From Packet to SoilGrowing Hardy Ferns from SporesGrowing Hardy Geraniums From SeedGrowing Lewisias From SeedGrowing Magnolias From SeedGrowing Meconopsis From SeedGrowing Proteas and Related Genera from SeedHandling Small SeedsHardy Annuals: Part 1Hardy Annuals: Part 2Hardy CyclamenHardy SpurgesHelleboresIncreasing your Violas and ViolettasKeeping Records of Seed SowingLettuce - the Vital Part of any SaladLord Anson's PeaMagnolias - the Root of the ProblemMimulus from Seed to Seed in Sixty DaysNew Guinea ImpatiensOld-fashioned Sweet PeasOnions with EverythingPansies are not Difficult to Grow from SeedParsleyPerennials for American GardensPetuniasPhygelius - their cultivation and propagationPinks: Evocation of the PastPlants That Flower OncePrickly but NicePropagatorsRadishesRaising PalmsRaising PrimulasSalad Leaves - a lot to be desiredShow Stoppers Twice OverSowing SeedsSowing in Open GroundSowing to Feed our FriendsSturt's Desert PeaSweet Peas - Autumn SownSweet Peas - Sowing and GerminatingTall and HandsomeTechniques with Tiny SeedTexas BluebellThe Effect of Light on Germination and SeedlingsThe Nervous PeaThe Scarlet Welsh PoppyThe Search for the Yellow Sweet PeaToad LiliesTomatoesTreasure Hunt for TasteUnderstanding Latin NamesUnique Poppy (Mother of Pearl)Viability of VegetablesWeaning SeedlingsWill the Real Mimosa Please Stand Up

Magnus Liden looks at the intriguing and increasingly popular genus of Corydalis.

Corydalis (or Corydallis) is the name the Greeks gave to the crested lark, and in Germany and Denmark the vernacular names Lerchensporne and Lúrkespore respectively have become attached to its vegetable counterpart in the Fumitory family. In Britain it is instead the genus Delphinium (sensu lato, including Consolida) that bears the epithet Larkspur.

The two genera share the zygomorphic (with one plane of symmetry only) corolla in which the upper petal is equipped with a nectar-containing spur, they are both rich in alkaloids, and you can find them in the gardener's catalogue, but there the similarities end. Whereas Larkspurs have long been popular, and come in a wide variety of hybrids and cultivars, Corydalis have only recently become fashionable and very little breeding has been done. A few species have a history as medicinal plants. Corydalis cava was cultivated in the medieval monasteries in Sweden, and indeed the Swedish name "nunneort" literally means the nun's herb. In the eighteenth century C. cava was frequently confused with, or substituted for, the highly valued Aristolochia rotunda. The common C. intermedia was collected in the wild and sold in pharmacies during the eighteenth century as a remedy for menstruation problems. In China, the boiled and dried tubers of "yanhusuo" are very important in traditional medicine to facilitate smooth running of blood in the veins, and several species are used in Kashmir. Corydalis has also been used as food; the Ainos are said to eat tubers, and some Himalayan tribes appreciate the spindle-shaped storage roots of C. juncea and other species of the section Fasciculatae.

In Britain there are no native species of Corydalis since the scrambling little annual Ceratocapnos claviculata and the garden escape Pseudofumaria lutea have been transferred to their proper genera. Five species are native to Sweden, in Turkey there are 15, in Nepal 43, and in China about 225.

Most of the species of Corydalis that are currently in cultivation are tuberous plants that sprout early in spring and have disappeared completely by the end of May or early June. There are about 80 tuberous species altogether, but as the genus numbers close to 400 species they are still a minority. Among the non-tuberous species we find annuals, biennials, as well as rhizomatous or rosulate perennials, and several of them deserve attention. In the early decades of this century, Wilson introduced the yellow-flowered C. saxicola (syn: C. thalictrifolia auct.), C. wilsonii, and C. tomentella from Central China, which are all easy to grow in a cold greenhouse, preferably in a tufa-wall. They are self-compatible and produce an abundance of seeds. Corydalis cheilanthifolia is fully hardy outside. Like the three just mentioned, it is easily grown from seed, and thrives in a variety of situations. The Japanese C. speciosa and heterocarpa are yellow-flowered biennials that may survive the British winter in favourable positions. There are also some annual species in the genus, most of them small-flowered and insignificant, but the common Chinese weed C.edulis has attractive pink flowers and looks nice in the beginning of the season.

The main centre for distribution of Corydalis is west-central China and south-eastern Tibet, and many sections of the genus are confined to this area. Only recently some of the rhizomatous perennials of the section Elatae have been introduced; C. elata and flexuosa. As they are very easy to propagate vegetatively, either from rootstock fragments, or from leaf-cuttings, they are rapidly spreading among Corydalis freaks, but are not yet available commercially. They are robust, densely leafy plants with blue flowers. Like so many other species in the genus, they are self-sterile, and have to be cross-pollinated to set seed.

A North American rhizomatous species, C. scouleri, is quite widespread in botanic gardens. It has a very attractive foliage that in dense stands forms an airy and lofty horizontal cover, with dense and narrow spikes of large pink flowers overtopping a sea of leaves. It grows best in a semi-shady spot.

Corydalis nobilis was introduced into Linnaeus' garden in Hammarby in 1765, and is now very widespread in Swedish and Finnish parks and gardens, it is also known to be naturalised in some localities. In Britain it seems to be less comfortable, but try it if you can get hold of it. The dense, almost globular, yellow flower-heads are most attractive, but regrettably it looks rather untidy in the fruiting stage.

The likewise yellow-flowered C. pakistanica is perennial, but often flowers the first year. It produces seeds in profusion, and seeds itself around. It is an attractive plant, with its glaucous leaves and crested flowers.

The great majority of species are alpine, and in the Himalayas there are some that grow in screes at an altitude of more than 6,000 metres. Studying Corydalis can thus be a rather troublesome endeavour. When you reach your study area after ten days walking, don't be surprised if you find the flowers powdered with snow and a frosty wind biting your cheeks. An hour later bumblebees forage around you, warmed by the sun, and guided by the lovely smell of C. latiflora.

A few species only are found in the woodlands on the south side of the main Himalayan range. C. chaerophylla is a common species which grows to a height of more than one metre. It has rather tiny yellow flowers, but they are numerous, and the attractive foliage makes it worthy of a place in the garden. C.flaccida has strange flowers variegated in blue and pink, and nice ornamental leaves.

Tuberous species

There are five sections, comprising about 80 species, that can be said to be tuberous. The section Corydalis is the largest among these, with close to 50 species, most of them amenable to cultivation, and hardy outside in South Sweden. The widespread European C. solida is perhaps the most valuable for garden purposes. It comes in a wide variety of colours, of which the pure red form known as 'George Baker' or 'transilvanica' is the most eye-catching, but there are also white, bluish, and pink forms, in addition to the muddy purple one that is widely naturalised in park environments in central Europe. In Greece and Albania ssp. solida is replaced by the lovely ssp. incisa.

Another species that is widespread in cultivation, is a Hokkaido/Sachalin plant with azure-blue flowers, commonly known as C. ambigua, but actually closely related to, if indeed separable from, C. fumarii-folia. This same beautiful colour can be found also in the recently introduced C. turczaninovii from south-eastern Siberia, north-eastern China and Korea, and in several other east Asian species. In an attempt to produce a plant with the Swedish colours, we have tried to cross this with the yellow-flowered C. bracteata, another hardy and vigorous species originating from central Siberia.

Although (in this section) each healthy tuber will produce two new tubers for the coming year, the fastest way to build up a stock is through seeds. Most species are self-sterile, but there are a few exceptions. The reddish-purple flowered C. caucasica is probably the most valuable of these. C. angustifolia is an attractive species with white or cream flowers, sometimes slightly suffused with purple, which are regularly self-pollinated. The related C. paczoskii is less attractive, but also regularly sets seed after selfing. The same is true of the small-flowered European species C. intermedia and pumila, but they are too insignificant to be of interest as ornamentals.

Turkey is a most rewarding country for Corydalis-hunters. Corydalis wendelboi is the most widespread and variable species, and it has become more and more common among alpine gardeners, It is replaced further east by several more conspicuous taxa, some of them (like C. henrikii and C. haussknechtii) recently discovered. In the north-east, the Caucasian species alpestris and conorrhiza from the section Dactylotuber grow in the mountains. They have both found their way into Britain on a couple of occasions, but are usually short-lived in cultivation.

Like most tuberous plants, the tuberous species of Corydalis thrive in summer dry climates, like in the Mediterranean area and central Asia. In late autumn roots are formed, and it is advisable not to let the plant dry out once root initiation has begun. Also the leaves and racemes of next year's growth are formed during this period, and thus all that is needed in spring is rapid cell-enlargement and shoot-elongation, triggered by the first warm sunrays.

The section Radix-cava counts for only four species, of which C. cava is the most widespread. C. parnassica is found on the high mountains of Greece, where its pale whitish or bluish flowers open close to melting snow. It is a very glaucous and low plant which stays dwarf and nice in cultivation.

Leonticoides is the next largest section of tuberous species with about 20 species, most of them from central Asia. One species only reaches Europe, C. uniflora from Cyprus, which is also the only self-compatible plant in this section. Among the best and most conspicuous species we have C. popovii which has become quite widespread. C. darwasica is also handsome, and some large-flowered forms of C. diphylla are really smashing. Mostly, the species of this section are a bit tricky in cultivation, and do not always live up to expectations, but the above mentioned three species are probably the best. The other species in the section may have quite remarkable flowers (C. afghanica can be cited as an example), but their stems are more or less weak and decumbent, especially in cultivation.

Sowing and growing

In most of the non-tuberous species the capsules are explosively dehiscent, and you must not be too late with your seed-harvest. Even with the tuberous species, seed-harvesting may give unsuspected surprises. This spring I collected seeds of C. shanginii, and temporarily put about twenty seeds on the shelf of the plunge-bed, while making a phone call. When I came back after a quarter of an hour, I was just in time to see the back of an ant carrying away the last of them. The seeds are equipped with fleshy appendages, elaiosomes, which are relished by ants, and obviously this is a very efficient mode of seed dispersal. The distances are usually not so great, but we once observed a Formica rufa transporting a seed of C. intermedia almost 15 metres. This mode of dispersal is quite common among plants. Take a look at the dispersal units of Hepatica nobilis, Dicentra spectabilis, Lamium album, or Chelidonium majus next time you pass them. Curiously, mice are deterred by the elaiosomes, and do not eat the seeds until they have been removed, all according to observations made in USA on C. aurea.

The seedlings of the non-tuberous species look quite normal for dicotyledons, but if you sow seeds of the tuberous ones, you may be surprised when they appear in the following spring. They germinate with one cotyledon only, which is also the only leaf produced in the first season. Young seedlings are susceptible to fungal diseases, and a treatment with fungicides is recommended as soon as the seedlings appear. Restricted careful watering is also important during this period. It is wise to leave the tiny tubers in the seedpan for a couple of seasons, in order to get them big enough to handle. Usually the tuberous species will not flower until their fourth year. The young plants are usually small and delicate, but they will grow larger and become more floriferous in subsequent years. Hopefully, you can look forward to a nice addition to the spring facet of your garden.

This is but a small sample of the immense variation of colours, growth forms and flower-morphologies that this fascinating and beautiful genus affords. The most gorgeous of the Chinese and Himalayan species are still waiting to be introduced. The scree-plants may be difficult to adapt to greenhouse or garden conditions, but, there are, for instance, several cliff-dwellers that make potential ornamentals. Next time you go to West Nepal, do not forget to procure seeds of C. staintonii, according to Stainton himself, probably the most beautiful of all Corydalis species.

Availability

Seed is not easy to find, the best bet is to check through the seed exchange lists especially those of alpine plant societies.