Growing Lilies in Greenhouses
The big advantage of a greenhouse or glasshouse is that the gardener can control the environment; lilies can be provided with warmth and moisture at the gardener’s, and not the weather’s, command. They can be forced into bloom much earlier with the proper amount of heat and correct lighting. This also means that lilies will start to growth earlier than they would outside and consequently the flowering season can be extended by raising early blooms inside. A greenhouse also lets the gardener attend to the plants at a convenient time, rather than be held up because the soil is too wet or frozen during the only time they have free. As with containers, the grower is able to control more accurately the medium in which the lilies are growing. A final advantage, and to many growers a very important one, is that lilies that are too tender to be risked outside can be grown.
Growing lilies under glass or in greenhouses seems the ideal growing conditions, but there are problems. Lilies need much more attention both with regard to watering and feeding. The worst problem is that pests and diseases also appreciate the ideal indoor conditions and become more difficult to control. Other pests and diseases that are not experienced outside may also occur.
The simplest way to grow lilies in glasshouses is in containers, but with the advantage of being able to control the atmospheric conditions. In winter, the temperature can be kept just above freezing, or, if earlier flowering is required, it can be stepped up to a minimum of about 45°F (8°C). During the summer the problem is keeping the glasshouse cool. As much ventilation as possible should be given and shading should be applied either in the form of netting or slats, or by applying a shading compound or white-wash to the outside of the glass. Evaporation of water sprayed onto the central path will also help to keep the house cool. Unless the pots are too heavy or there is nowhere to put them, many can be moved out into the open during the summer, which will give the lilies a more natural atmosphere. Do not put the lilies out if heavy rainstorms are expected.
Lilies in a greenhouse or under glass need not be confined to pots. It is possible, and indeed preferable in some cases, to grow lilies in a specially prepared bed in the glasshouse. Stoloniferous lilies, which ‘wander’ through the soil, prefer this. The bed can be excavated from the floor of the house or built up from it in the form of a raised bed. The soil used should be the same as used in containers and the treated essentially the same. With a bigger volume of soil, the bed will not dry out so quickly.
Whether the bulbs are in containers or in beds they can be planted in autumn, mid winter, spring,(even early summer) and treated the same as container plants grown outside. Particular attention must be paid to any pest or disease that invades the greenhouse, as once present pests and diseases can build up to devastating proportions in a very short time.