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Hellebores - Thompson & Morgan

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Hellebores

Brian Mathew describes this genus which has been growing in popularity in recent years.

The best advice for anyone who is intending to grow Hellebores from seed is to get them into the ground as soon as possible after they are ripe, which is usually some time between late spring and early summer. In the wild state Helleborus species mostly grow in light woodland or grassy situations, which are never excessively sunbaked. The seeds, when they fall, are attractive to ants who unintentionally 'sow' them into the soil where they are protected from extremes of temperature and drought. Having survived the summer they then receive a cool damp autumn and winter period which triggers the germinating process. It is a frequent complaint by gardeners that Hellebores, although carefully sown in pots will not germinate, or at best very poorly, while self-sown ones beneath the parent tend to come up like proverbial mustard and cress. The primary reason for this is, I am sure, the delay between collecting the seeds and sowing them; for most people tend to keep their seeds until autumn, winter or spring before dealing with them. During this delay period of a few months in summer the most obvious way to store seeds is in envelopes or paper bags which allow them to dry out, thus largely avoiding the possibility of fungal attacks. However with Hellebores this appears to be the wrong treatment and in drying out a sizeable percentage apparently lose their viability. I have found that there are two ways of overcoming this, either by sowing the seeds directly they are gathered and keeping them watered through the summer, or by storing them for the summer in polythene packets or tinfoil and then sowing them in autumn as usual. The treatment from autumn onwards is the same for both methods; the seed pots or trays being placed out in an open bed or cold frame where they will receive frost treatment. Germination will normally take place at some time in the winter and at this point, when the seedlings are showing their two cotyledons but no true leaves, they are best moved into the protection of a frame or unheated greenhouse.

During the winter or early spring the true leaves start to appear, at first with only 3 to 5 leaflets, and this is a good time to pot them singly, keeping them in the cold frame or greenhouse until well-developed in spring. If growing strongly they can be planted out in April or May into a prepared bed of well-drained soil, preferably one into which decayed organic matter has been worked. Through the early summer progressively larger leaves are produced if conditions are right. Growth can be helped along by the use of a general purpose liquid fertiliser. Really strong plants may flower the following spring, just over one year from germination, but it is much more likely that they will require two whole growing seasons or even three before flowers are seen.

The compost for the seeds and for potting-on may be one of the soil less types or a loam-based one such as John Innes, and I find that the seeds are best covered with a fairly coarse grit after sowing; this allows the seedlings to push through easily, prevents compaction of the soil surface during heavy rains, and deters liverworts to some extent.

The main Hellebores to be cultivated by gardeners are the Lenten Rose varieties in a wide range of colour forms from white to pink, plum and deep blackish-purple, often conspicuously spotted reddish-purple. These are mostly selections of H. orientalis, a species which inhabits northern Turkey and the Caucasus where it varies to some extent but shows nothing like the range which is to be found in gardens. The 'orientalis hybrids' are excellent garden perennials, long-lived, hardy, floriferous and at their best in late winter at a time when there is little else other than some early bulbs. They thrive best in a semi-shaded site where there is plenty of moisture available, so heavy soils are not a problem, and they are equally at home in acid or alkaline conditions. To maintain a particular colour form, absolutely true to type, it is necessary to divide an established clump in autumn or early spring, since plants grown from seed will almost certainly vary considerably. However, in raising new ones from seed there is always the excitement of the unknown, every batch presenting the possibility of a few especially good forms.

The much-loved Christmas Rose is, I find, less easy to please, although in some parts of the country it is a great success. Seldom do I have flowers for January, let alone Christmas, but nevertheless it is worth every effort to get a few of the beautiful snowy-white blooms during the depths of winter. This species, I find, does best if grown from seed and the young seedlings planted out into their permanent positions at an early stage so that they can grow on unchecked through to flowering size. The most successful plants seem to grow on rich alkaline or neutral soils, heavy clay being quite acceptable as long as it is well supplied with humus. The Christmas Rose does not vary as much as H. orientalis, all forms being white-flowered although some of them rapidly change to a pinkish colour as they age. Here again, individual forms, if required true, must be propagated by division, but it is a slow business to build up even a small stock and by and large it is better to grow from seed saved from good forms.

Some Hellebores have tall rather woody stems carrying clusters of pale green flowers at the apex and these types are rather striking, useful as 'dot' plants in the garden for a bold effect. The British native Stinking Hellebore (it only smells when bruised and then not badly), H. foetidus, has attractively divided deep green leaves crowned by paler clusters of bracts and flowers, visible for most of the winter and spring. Although the flowers are small and bell-like, there are a lot of them so this is really quite showy in its own quiet way. Self-sown seedlings of this one are likely to appear in the garden and I find that it tends to prefer the edge of the gravel driveway rather than the open border. The Corsican Hellebore, H. argutifolius (H. corsicus), has much larger green flowers in a sizeable cluster crowning the leafy stems. Each. leaf has only 3 lobes so the foliage is rather distinctive, and in addition the margins are sharply spiny, much more so than in any other species, so there is no chance of confusion. This species may also seed itself around in gardens where it is happy, and on the whole it seems to prefer sunnier positions than most Hellebores, although not too hot and dry, nor too exposed for its stems can be flattened during inclement weather. After flowering the stems are replaced by new ones so at this stage it is a good time to prune out the old ones, although if seeds are required the pruning must be delayed until the pods are ripe. Should one be lucky enough to acquire a plant of its near relative from the Balearic Islands, H. lividus, it must be remembered that it is a tender plant so a sheltered, partially shaded spot should be chosen. This species is shorter and stockier and has non-spiny leaves which are beautifully veined with cream on a bluish-green background, while the undersides of the leaves, and the flowers, are tinged with a warm pinkish-brown colour. Much more commonly seen in gardens is the hybrid between these two, known as H. x sternii after Sir Frederick Stern in whose garden at Highdown it was first noticed. This has the taller habit of H.argutifolius, and slightly spiny-edged leaves, but the influence of H. lividus shows in the form of a pinkish-purple suffusion on the flowers and somewhat creamy veins in the leaves. Unlike many hybrid plants H. x sterna is fertile and produces plenty of seeds which give rise to a variable range of offspring. Another attractive but rather rare hybrid is H. argutifolius x H. niger, called H. x nigericors, which has a shrubby type of growth like the former but with clusters of large whitish-green Christmas Rose type flowers. This unfortunately is sterile so to obtain more plants it is either necessary to divide an established clump, if one is lucky enough to have access to one, or repeat the cross and obtain fresh seed; this is best done using H. niger as the seed parent, transferring pollen from H. argutifolius, or from H. x sternii which works just as well and can produce nice results. These latter crosses have become known as 'Nigristern' hybrids.

Apart from the species I have mentioned above there are about eight more which are not commonly grown in gardens and might be termed specialist plants, for they are much less showy than the others. Five of these have green flowers, the most widespread of which is H. viridis, our British native Green Hellebore which may also be found over much of western Europe. This and the similar H. dumetorum from Yugoslavia has small unscented green flowers. Rather larger and with a distinctive scent reminiscent of Blackcurrants is H. multifidus which, although not a striking plant in flower does have attractive leaves divided into a great many slender leaflets; this is from Yugoslavia and Italy. The largest flowered of the green ones are H. odorus and H. cyclophyllus from Yugoslavia and Greece respectively. Both are well worth growing for their sizeable clear green flowers which have a strong scent, although some people find it disagreeable. Both will hybridise with the Lenten Rose and by crossing either of these white forms of H. orientalis quite good yellows can be produced.

In south-eastern Europe there are three purple-flowered species which, in their darkest forms, may be an exciting blackish-blue colour. These are H. purpurascens, H. atrorubens and H. torquatus. Since they will also cross with H. orientalis they are very useful for imparting darker tones into the Lenten Rose cultivars, H. torquatus in particular having been used in the past for this purpose. Cultivars such as 'Black Knight', 'Ballard's Black', 'Pluto' and' 'Blue Wisp' derive their fascinating colour from this species. The bluish tones are caused by a greyish-blue grape-like 'bloom' covering an otherwise dark blackish-purple flower. In their true wild forms all three of these are well worth growing but are, unfortunately, rather rare in cultivation at the present time. However, as garden plants, the hybrids certainly give better value with their larger flowers and increased vigor.

Although it is usually fairly expensive to buy a plant of one of these darker hybrids it is worthwhile, not only for the joy of growing the plant itself, but also in order to introduce a new colour into one's own seedlings. This crossing need not be done in a laboriously controlled way, for if several different forms are planted together the early spring bees will do the job. However, if a more certain outcome is wanted, a few minutes with a paint brush on warm sunny days, transferring pollen from the stamens of one flower on to the stigma of another, will usually result in a fine crop of seeds which should produce a varied range of plants including, hopefully, some pleasant surprises. On the whole I find that the most difficult problem over growing Hellebores from seed is in deciding which ones to dispose of, for they are robust plants each taking up at least a square foot of garden so there is a limit to the number of seedlings I can grow on. Having nurtured them to flowering size I find it an agonising business to actually dig some up and throw them away! Some growers are built of sterner stuff than I and can bring themselves to burn or compost these inferior seedlings, but mine usually end up as a 'lucky dip' box for friends or at a charity plant sale where they are much appreciated. With these mixed Hellebore seedlings it is largely a case of all being nice, but some are better than others!

Brian Mathew is a Scientific Officer at the Royal Botanic Gardens, Kew.

Source of article
Growing From Seed - Autumn 1988 Vol. 2 Number 4
© The Seed Raising Journal from Thompson & Morgan