Obtain, in autumn wherever possible, plump, healthy bulbs of good varieties, from a reputable source.
Plant the bulbs immediately in a well drained site. If drainage is poor and cannot be easily improved, plant in raised beds. Lily bulbs, except Lilium candidum, should be planted in a hole or trench with a depth about three times the length of the bulb. Lilium candidum likes shallow planting and should never be planted with more than 25mm of soil over the top of the bulb. Nearly all lilies will thrive in full sun or partial shade.
Protect the root run from high soil temperatures with a mulch or low growing companion plants. In nature, most lilies are found in association with low-growing, shrubby bushes, or perennial plants. They do need to get their heads up into the sun.
Lilies are not particularly heavy feeders and if forced will tend to put on sappy growth which is particularly attractive to sap-sucking insects and fungal diseases. However, they do require regular feeding which is generally best achieved via balanced fertilizers applied at planting time or on emergence in spring. Pelletized manures or slow-release products are generally suitable, but unless they specifically contain trace elements, these should be provided also.
Where heavy frost is anticipated after emergence, planting under large trees or shrubs will afford some protection, as will any overhead cover. Since frost always runs downhill, areas below fences or buildings will give some protection whilst areas above such structures will be at greater risk. Most hybrid lilies are relatively resistant to pests. Good housekeeping will further assist this process. Remove all old stems and foliage as they begin to yellow in the autumn. This is best done by cutting at an angle just above ground level. Should a significant infestation of aphids or similar insects occur, they can be treated with an insecticide. The less hazardous types such as Clensel® are recommended. Note that heavy usage of even these products will destroy beneficial predators which usually keep these pests under control. Use snail bait as required, especially when the stem “noses” emerge in spring.
Similarly, good housekeeping will keep most diseases at bay. Maintaining good air drainage by not over-crowding or blocking out all winds will assist the process. Watering is best carried out early in the morning so that remaining water will not remain on the foliage any longer than necessary. Fungicides may be used, but generally give mixed results. Botrytis is the major problem, and will appear as spots on foliage or flowers during humid conditions. The odd spot of botrytis will generally not have any longer term effect on a bulb.
Virus infection may occur, and when confirmed, the only solution is removal of the plant and safe disposal so as not to infect others. Many minor problems may present similar symptoms to virus, and care should be taken to ensure that the symptoms are not simply the result of minor damage or nutrient deficiencies. Symptoms of concern would include mottling of leaves and/or flowers. When cutting flowers, always disinfect secateurs with methylated spirits between plants to avoid spreading the infection.
Remove spent flowers and do not allow seed pods to form unless they are specifically required. Whilst lilies will survive without this treatment, the energy directed to producing seed pods will detract from next year’s bulb development. When cutting flowers, always try to leave at least one-third of the stem and foliage to replenish the bulb for next season.
Lilies require moist conditions but will not tolerate wet feet. Waterlogged basal root systems are by far the greatest killer of healthy bulbs. Plants weakened by such conditions will also be far more subject to the ravages of pests and diseases. Note that it is what happens below the top-soil, at the sub-soil level, which determines what will happen – a sloping soil surface is no guarantee. Enhancing drainage with sharp, coarse metal layers and raised beds will certainly assist, as will a good micro-irrigation system. Lilies must never dry out as with daffodils or gladioli.
There is no need to dig your lilies unless they are becoming over-crowded or showing other signs of deterioration. When digging, try to replant immediately to avoid drying out. If this is not possible, pack the bulbs in moist sphagnum moss and keep out of the sun and wind until you can replant. In Tasmania’s relatively mild conditions, bulbs should be lifted at any time after the foliage begins to yellow.
If you enjoy lilies and would like to share your experiences with others and learn more, consider joining a Lilium group, preferably in your region. The benefits can be substantial and may include meetings and newsletters, shows, bulb sales, seed dispersal programs, libraries, bulk purchasing benefits and more.