Erythroniums

Brian Mathew examines this fascinating and most garden-worthy group of plants

There can be few plants which are more attractive than the Erythroniums, a delightful group of spring bulbs which grace the woodlands of a vast area of Europe, Asia and North America with their distinctive reflexed-petalled pendent flowers. As garden plants, they can scarcely be faulted since they are beautiful, on the whole easily cultivated, and appear to suffer from few pests or diseases.

Both the vernacular and botanical names of the Dogs Tooth Violet (E. dens-canis) refer to the shape of the bulb which is elongate and pointed somewhat like a canine tooth. It is said that the plant was known to the ancient Greek herbalists but I have my doubts since no Erythronium occurs in the area which they occupied and it seems unlikely that they would have exterminated them completely during the course of their medicinal activities! A much more likely explanation is that Erythronium, from a Greek word meaning red, referred in ancient times to a quite different plant from that to which later botanists applied the name. However it is certain that the 16th century herbalists such as Gerard were advocating the use of Erythroniums as we know them today. 'Put in children's pottage against worms of the belly' is one way of using up surplus bulbs when you have propagated too many, but a more entertaining experiment would be to test Gerard's recommendation that 'it provoketh bodily lust if it be only handled, but much more if it be drunk with wine'! Tempting as this potion may seem, I feel that Erythroniums give much better value if they are planted out in the garden and enjoyed for their charming spring display.

Apart from their graceful flowers, most of them also have decorative foliage, the pair of basal leaves being marbled brown or purplish on a green ground. In addition to these noteworthy features, the Dogs Tooth Violets are not particularly difficult to propagate, although from seed they are rather slow to reach flowering size, between three and five years. Of course, the quickest way to achieving a display is to buy bulbs in the autumn, and these should be planted as soon as they are received, since they will not tolerate being dried out for too long. Good suppliers will have stored and packed them in such a way that they are not desiccated before they are sent out. Some species and cultivars, when growing well, increase vegetatively so efficiently that they soon form clumps of bulbs which can be lifted and divided from time to time, in the early autumn. Into this category come E. tuolumnense, E. 'White Beauty', E. 'Pagoda' and E. dens-canis in all its many forms. There is thus no need to raise these from seed, and in any case some of the hybrids are sterile so the possibility does not arise. However quite a number of the species do not increase in this way and the only method of building up a small stock is to sow seeds. If this is not available from one's own plants it might be obtained from those seed suppliers who specialise in the rather more unusual plants, or from the seed lists of the various alpine and hardy plant societies.

In nature Erythronium seeds ripen during late spring and early summer and are scattered more or less immediately, to be covered rapidly by other vegetation or by dead leaves or stones depending upon the habitat. Although they will remain fairly dry through the summer they will not be exposed to scorching sun and extremes of drought. The cool damp autumn and winter weather which follows triggers off germination and the young seed leaves will appear above ground at any time during this period, although in the case of the mountain species the whole process is delayed until the spring. In cultivation we can imitate this and sow the seeds as soon as they are ripe, then place the pots out in a shady corner to be watered lightly through the summer. If however they are to be acquired from a seed supplier or seed distribution scheme it will almost certainly be winter before they become available so in this case they should be sown immediately and left outdoors to receive the winter weather, since it is fairly certain that a period of cold, perhaps even frost, is necessary to stimulate germination. Proprietary brands of seed compost appear to be satisfactory and, although it may seem sacrilege to the makers, I find that mixing a loam based one such as John Innes with a 'soilless' one in 50:50 proportions produces a very acceptable blend which has the right 'feel', not very scientific but the results are reasonable!

Opinions vary as to how long Erythroniums take to flower from seed, some growers claiming as little as 3 years, others as many as 7 but I am sure that it partly depends upon the species involved. I would expect flowers in 3 or 4 years if the growing conditions are good, and I think that development is quickest if the young seedlings are planted out into the open ground after one complete growing season. If the seeds are sown fairly thinly the whole pot ball can be knocked out and planted directly into the final position. All the Erythroniums require is a semi-shaded border where deciduous trees or shrubs will allow dappled sunshine and rain to filter through in the spring and provide cool shade later on so that the dormant bulbs do not become too hot and dry. The soil should be well drained and deeply cultivated with a good humus content, preferably in the form of leaf mould or well-rotted garden compost. They appear to thrive best in slightly acid conditions but they can be grown on chalky soils if plenty of humus including peat is incorporated.

There are about 20 species and they are nearly all North American except for E. dens-canis which is widespread in Europe and, in one form or another, is to be found right across the Soviet Union and on into Japan. Some authorities regard these geographical variants as distinct species so that we find the names E. caucasicum E. sibiricum and E. japonicum given to some of the more distinct forms. The most likely one to acquire is the European version which is usually available as a mixed collection of colours from white to pinkish lavender or a stronger purplish shade. Individual colour forms have been given cultivar names such as 'Snowflake', 'Rose Queen', 'Pink Perfection' and 'Purple King', and some nurserymen list these separately. All the forms have attractively mottled leaves and are good foliage plants although the leaves die away for the summer months.

The North American species are fairly numerous but fortunately their identification is simplified somewhat because they can be grouped on the basis of flower colour and whether they have plain green or mottled leaves. Thus the white flowered species may be divided into plain green leaves or mottled leaved groups and the yellow flowered ones, on the same basis, into two more groups. The remaining flower colour, pink or lilac, is only available with mottled leaves, evolution apparently not yet having caught up with that particular subtlety!

The beautiful Avalanche Lily, E. montanum, which carpets the alpine meadows of some western American mountains, is the main representative of the group with plain foliage and white flowers. It is scarcely known in cultivation since it appears to be as near to impossible to cultivate as any bulb that I know. On the other hand the white flowered ones with mottled foliage are among the easiest to grow. The most likely one to be encountered is E. oregonum which has large pure white flowers with a contrasting zone of brown markings near the centre. There is little to choose in terms of garden value between this and its near relative E. californicum which has slightly differently shaped stamens with white, rather than yellow, anthers. E. multi-scappideum, also from California, is very like E. californicum in its floral details but the flower stem branches low down, at about ground level, giving the impression of several stems per bulb. E. helenae might be found in some seed lists and this too is a rather attractive plant with a large yellow centre to its white flowers, also Califomian. There is one species from the eastern United States which might be considered, although it is not showy compared with its western cousins. It is E. albidum, a rather small-flowered species with a flush of bluish or purplish colour on the outside. Its main attraction is the beautiful mottled foliage overlaid with a greyish-blue grape-like 'bloom'.

The group containing the yellow-flowered species with plain leaves has given us one of the most easily cultivated Erythroniums in E. tuolumnense which grows wild in the foothills of the Sierra Nevada mountains in California. It is a vigorous plant with bright yellow flowers, several on each stem held above the bold light green foliage, and it has the added attraction that it increases rapidly into clumps. E. grandiflorum, a beautiful dwarf species in the wild, can be seen on many of the western American mountains in thousands soon after the snow recedes. Although it can be cultivated reasonably well on a peat garden or in cool woodland conditions it never makes as much of a show as its more sturdy Califomian relative. To find the combination of yellow flowers with mottled leaves we must travel east to the eastern United States where there are several answering to this description, but only one which is known at all well in cultivation. This is E. americanum which forms enormous patches in the wild by producing stolons from its bulbs but unfortunately it does not flower very freely so that there are usually many more leaves than flowers. Sadly it does this in cultivation as well but nevertheless is so easy to grow and such a pleasant foliage plant that it is well worth growing in a seldom-cultivated partially shaded spot where it can follow its stoloniferous habits undisturbed. The flowers are yellow with a coppery stain on the outside, and this colouration is repeated in the less well-known E. umbilicatum, another species from the eastern United States. As a garden plant this does not appear to be quite so accommodating and it seems that cultivation in a deep pot in the alpine house or cold frame is the most satisfactory method.

The final group, comprising the pink and lilac flowered species which have mottled leaves, gives us two of the best of all the Erythroniums. E. revolutum, which is widespread at low altitudes in the western States, is robust with large rosy pink flowers, varying somewhat in the depth of colour so that some selections have been made, including var. johnsonii and 'Pink Beauty'. However, a batch of seed will often produce a range of shades so it is not entirely necessary to hunt for these named variations. In Oregon and northern California occurs the exciting E. hendersonii, the only species to have lilac flowers with a blackish-violet eye in the centre.

Both of these are easily cultivated but neither of them produce offsets very freely so that they are not normally clump-forming and seed represents the only practical method of increase.

Apart from the above mentioned species there are a few hybrids which are extremely good garden plants, easier to grow and increasing prolifically by vegetative means. The most well-known is undoubtedly 'White Beauty' which has attractively mottled foliage overtopped by creamy white flowers zoned with brown in the centre. This is very similar in most respects to E. californicum and may actually be a selection of it rather than a hybrid. The yellow flowered E. tuolumnense has passed on its vigour to 'Pagoda' and 'Kondo' which both have large, slightly patterned leaves and pale yellow flowers, the stronger yellow of the species having been 'watered down' by the whitish flowers of 'White Beauty', the other parent. 'Jeannine' is another similar cross with very large rich yellow flowers which have a white eye, and there are also some more recent tuolumnense x oregonum hybrids raised by Mr. John Walker which show great promise, although they are not generally available yet. Clearly there is plenty more scope for hybridisation although it is not known at present if there are any genetical or other barriers between the species. The lilac and pink E. hendersonii and E. revolutum have scarcely been tried for breeding purposes so for those who are interested in trying to raise new garden plants there is room for experimentation. The process of cross-pollination is very simple with such large flowers and it is merely a case of removing the six stamens from the proposed seed parent and transferring pollen to its stigma from the male (pollen) parent. It is worth repeating this several times over a period of days in order to catch the stigma at its most receptive stage. For the purist the flower should be protected from wandering bees which may have already visited some other Erythronium so a muslin or net curtain 'cage' should be placed over the whole plant. Above all, do keep records of the parents, for already there are far too many garden hybrids around with unrecorded parentage.