Growing Lilium and Avoiding Disease and Infection
Lilies were a very varied lot long before man came on the scene and began to take a hand in their diversification. Over eight hundred species have been recorded growing in the wild and a number of these are cultivated in gardens, though in recent years they have tended to be supplanted by manmade hybrids. Whether this is entirely a good thing is open to doubt. The hybrids have certainly produced new colours and forms and some magnificent plants, and some of them are easy to grow. But few actually surpass the best species either in beauty or in vigour and it would be a great loss if over-preoccupation with the hybrids led to neglect of the species.
Lilies flower in four basic forms: trumpet, bowl, turk’s cap and cup-shaped. The trumpet is the classical lily shape and varies from very long and slender, as in Lilium formosanum, to broad and fairly short, as in the ever-popular L. regale. The bowl shape is best exemplified by the magnificent L. auratum, which when fully open can have almost flat flowers 20-25cm (8-10in) across. The turk’s cap, or reflexed, is a widespread and familiar form with the flowers usually hanging downwards and the petals always swept back at the tips, as in L. martagon, L. tigrinum and L. chalcedonicum. The flowers of cup-shaped lilies are usually carried in upward-facing clusters; examples are L. bulbiferum, L. hollandicum and L. maculatum.
All lilies make bulbs but these do not have an extended resting season and do not like being out of thefor long at any time of the year. Once established in the garden, lilies are best treated like , to be lifted, divided and replanted as quickly as possible — and only when this becomes necessary because they are overcrowded or for some other reason. The best time to do this is as soon as the leaves have withered, which for early-ripening kinds, such as the Madonna lily, L. candidum, and its apricot-yellow hybrid L. testaceum, is usually in July or the first fortnight in August, and for late-growing kinds, such as L. speciosum and L. auratum, not until late October or early November.
Bulbs from distant places such as western North America and Japan may not be available on the market until midwinter and it is a very chancy matter planting them directly out of doors. Usually it is wise to pot them singly in 10-15cm (4-6in) pots according to the size of the bulbs. Use a peat-based potting(lime-free for lime-hating kinds) and keep them in a frame, cool greenhouse or other light but protected place until they are growing freely in the spring and can be planted out with roots and compost intact. If home-grown in Britain are available, it may be possible to obtain delivery much earlier and then it is usually best to plant them at once where they are to flower.
All lilies like porous yet fertile soil, moist in spring and summer when they are making their growth but for most (there are exceptions) not waterlogged in winter. They like humus in plenty because it helps to maintain these conditions and a good many lilies dislike lime in the soil, preferring it to be moderately acid. Again there are exceptions, and plenty of lilies will grow perfectly well in neutral or even moderately alkaline soils.
Another difference between lilies is in the way they form their roots. Some make all root growth from the base of the bulb and some have a second root system growing from the base of the stems above the bulbs. Clearly it is better if these stem-rooting kinds are planted sufficiently deep to give scope for this upper root system to be developed; but since nearly all lilies, stem rooting or otherwise, grow well when covered with 10cm (4in) of soil, the distinction is not quite so important as is sometimes suggested. The two principal exceptions are L. candidum and L. testaceum, both of which like to grow virtually on the surface with the tops of their bulbs exposed.
Lilies grow well in open places provided they do not become dry and sun-baked in summer. They often grow even better in dappled or intermittent shade or when planted among low-growing shrubs and leafy perennials (evergreenand herbaceous peonies are excellent), which will shade the soil, keeping it cool and moist, but will allow the lily stems to grow up into the sunshine.
When planting lilies, it helps to surround the bulbs with a mixture of equal parts soil, peat (or leafmould) and sharp sand (or perlite) to. Which a light peppering of bonemeal or John Innes base fertilizer has been added. This same mixture is ideal for lilies that are to be started in pots and planted out later on. All lilies can also be grown throughout in pots in unheated or very slightly heated greenhouses or in otherprovided they get a reasonable amount of light. Pots should be big enough to give the lilies plenty of rooting space.
Disease and Infections that Affect Lilies
Some lilies are very sensitive to virus infections which rapidly debilitate them and render them useless. Other kinds seem able to survive such attacks with little outward sign of harm and this, though satisfactory in one way, can be dangerous in another since the virus-tolerant lilies can become unsuspected sources of infection for the virus-sensitive kinds. L. tigrinum is a notorious virus carrier and is best kept out of the garden if virus-prone lilies, such as L. auratum and L. speciosum, are to be grown. There is no easy remedy for virus diseases but they are spread mainly by greenflies, so periodic spraying with aphicides will help reduce the risk of infection.
The other principal disease of lilies is grey mould caused by the fungus Botrytis cinerea, and this can be particularly troublesome with L. candidum, the leaves of which can be severely disfigured by the time the flowers open. Grey mould is difficult to cure but infection can be prevented by occasional spraying in spring and summer with benomyl, thiram or a copper fungicide.
Many lilies can be raised from seed and some, notably L. regale, L. longiflorum and L. formosanum, grow so rapidly thatwill flower the first year and quite a high percentage can be expected to flower the second year. Seed can either be sown in late summer or autumn, as soon as it is ripe, or the following spring. It is best sown in pans in a compost of equal parts soil, peat and either sand or perlite, and germinated in a greenhouse or frame without artificial heat. The seedlings are best left undisturbed for the first summer, but in the autumn they can be potted in 7cm (3in) pots and by the end of the second year most should be sufficiently large to be planted outdoors.
Lilies can also be increased by splitting up the bulb clusters. This is done at the normal planting season for the species or hybrids. Lilies can also be increased by detaching scales from the bulbs and pressing these to half their depth in a mixture of equal parts peat and either sand or perlite. If kept moist in a frame or cool greenhouse most of the scales will soon form little bulbils at the base and after three or four years these can be grown on to flowering size. Scale propagation is a useful means of increasing, fairly rapidly, stocks of hybrids and garden varieties which do not breed entirely true from seed. Species, which do grow true to type from seed, are better increased in that way since seedlings will start life virus-free whereas scales will be infected by whatever viruses their parent plants were carrying.
Some lilies, including L. tigrinum and L. bulbiferum, carry little bulbils in the axils of the leaves up the flowering stems and these can be detached and grown on into flowering-sized bulbs. This is a very easy means of increase and the bulbils produce plants exactly resembling their parents.