Lilies can be propagated using a variety of different methods. They can, of course, be raised from seed which has many benefits. Not least of these is avoiding the transmission of viral diseases. Details of appropriate composts, containers and techniques can be found here: Growing from seed
The main vegetative methods of propagation are the use of bulbils, bulblets, scaling and division and these are all easy and successful techniques for the amateur lily enthusiast. The grower must, however, be aware that it is of the utmost importance that only material from healthy and virus free plants should be used for these cloning techniques. There are a few other methods, such as meristem tissue culture, which are not really appropriate for the average grower and so will not be covered here.
A few lily species, such as L. lancifolium, L. sargentiae, L. sulphureum and some forms of L. bulbiferum regularly produce bulbils in the leaf axils. Non-flowering individuals are often particularly prolific in this respect and even quite young plants will usually produce one or two. Several other species will sometimes produce bulbils on the upper stem if flowering is frustrated for some reason.
Often the bulbils will begin to produce leaves and small roots whilst still attached to the maturing green stem and both are visible in the following photograph of another form of L. sulphureum which is believed to have originated in Myanmar and been grown by Sir Peter Smithers in Switzerland.
Once the bulbils are sufficiently large (about the size of a small pea) they should be picked carefully and sown in the same way as seeds.
A variety of containers can be used, clay or plastic, and a good gritty compost. One part gritty lime-free garden soil, one part coarse lime-free grit, one part fine composted pine bark is a mix which has been used successfully. A simple alternative is half ericaceous mix, half coarse lime-free grit. A smaller proportion of grit may be better in well drained clay pots.
Prepare pots of compost as described in Growing from seed
Place the bulbils separately on top of this compost. About nine is right for a 14cm pot.
When all the bulbils are in place, top the pot with about 1cm thickness of the same compost mix and firm gently.
Then all that is required is that the pot is labelled, watered with a fine rose and placed in a sheltered spot. Most bulbils will be ready in late summer and if they are potted up at that time will produce some roots and possibly leaves whilst the weather is still fairly warm. Once they have become dormant the pot can be kept just nicely moist by sealing it in a clear plastic bag until growth resumes in the spring.
Keep the young lilies in their pot until they are a good size. Then pot on in a similar compost with a slow-release fertiliser, or plant out in well-drained soil or a raised bed. This is often done after foliage has died down but the young plants can be successfully moved on whilst in growth if great care is exercised.
If you have too many bulbils to pot in this way then they can be planted in rows in the garden or under glass, or you could use boxes or trays. Standard seed trays are not really ideal as they are not deep enough but they can be pressed into service if you are happy to carefully move the young plants on early in the next year.
Many lily species and hybrids will produce bulblets at or just below the soil surface and if simply left in place to grow on they will help to build up an attractive clump in the garden or pot.
This is how lilies look at their best, rather than as isolated individuals, and most resent disturbance once established. However, there may be occasions when the grower wishes to produce some new plants and these bulblets can be used without the need to lift the ‘parent’ bulbs.
The process is very simple. In late summer or early autumn carefully scrape away the surface soil or compost until the bulblets are exposed. Then pull them away. They will probably already have rooted so some damage is inevitable but try to keep as much of the root as possible. All that is then required is that they are potted using a gritty compost in well drained pots, labelled, watered and stored until growth begins in the spring. They can then be grown on and planted out when large enough.
Scaling involves greater disturbance to the ‘parent’ plant but can be a useful method in some circumstances. If it proves impossible to produce seed and the plant doesn’t multiply itself by other means then this may be the only practical technique available to the amateur grower. The method involves removing some or all of the bulb scales. It may be that some scales are accidentally detached when moving lily bulbs to a new position and these should certainly be used to produce a few fresh plants. Some lilies, such as the western American species with rhizomatous mat-like bulbs, are especially prone to this, as is L. medeoloides.
If you decide to try this technique then the first step is to lift the ‘parent’ bulb. The example in the photographs is a bulb of L. pardalinum. Alternatively it is sometimes possible to carefully move soil away and expose enough of the bulb to be able to remove a few scales without too much disturbance.
With a bulb like this the old scales will work just as well as the newer ones so it is best to use these and then the bulb may be replanted. The scales should be carefully removed, breaking them off as close to the basal plate as possible.
There are different ways of treating the scales. Some growers place them in plastic bags with compost or vermiculite and then pot them once small bulblets have formed. This needs to be done very carefully to avoid damaging the tiny young bulbs and roots. Probably an easier method is to prepare some pots in the same way as described for bulbils and to insert the scales with just the very tips showing.
Water the pot and allow it to drain and dry a little. Insert a label and then seal in a plastic bag as was described for bulbils. The scales will produce small bulblets on the callus which forms at their base.
The bulblets will usually grow away in the spring and can be cared for in the same way as seedlings or plants from bulbils.
As mentioned earlier, lilies generally look better when they have become well established colonies, such as this group of L. superbum.
However, occasionally it may become necessary to lift and divide very congested clumps if their performance and floriferousness begin to decline. This is most likely with species like L. speciosum when grown in pots. After a few years the bulbs will have divided naturally and produced many bulblets which will have grown on in the pot. A similar situation may arise with some species in the open garden making division a good idea. Some damage to the bulbs and their roots is unavoidable but try hard to keep this to a minimum. The best time to undertake this task is in late summer when the soil is still warm and the lilies will have time to produce some new roots before the onset of winter. You can find advice on potting and replanting the bulbs here: What do they need?