Mostcan be grown from seed. This is the slowest method of propagation but the cheapest, and the stock is free from disease. Seeds can be sown as soon as they are ripe, or kept until the following spring. Sow them about 1 in. apart in a well-crocked box of John Innes seed compost, and cover them with about an inch of fine soil.
Some seeds make a little bulb but do not show a sign above ground until the following spring, so do not be in a hurry to throw away apparent failures. Some lilies are fairly quick to flower from seed, others take five to seven years.
can be increased from scales provided the stock is healthy. Take a few scales from a mature bulb (which can afterwards be replanted), and ‘sow’ them in a seed box, in a layer of coarse sand or vermiculite on top of John Innes seed or potting compost. This can be done at any time of the year, but the late summer, when the flowers are over, is the best.
Place the scales, at an angle of about 45°, with the severed edge downward and the hollow side uppermost. Sprinkle over them enough sand to just cover them (or with the tips just peeping through), and keep them moist. Put the box where a temperature of 50 to 55° F. (10 to 13° C.) can be maintained. Littlewill form on the broken edges of the scales.
These are little purplish-black or greenish growths like boot buttons growing in the angle between the stem and leaves — the axil. They are produced by L. bulbiferum, and L. sargentiae and some of their hybrids. Treat the little bulbils as if they were seeds, or just lightly press them into the top of the soil in a box. They are ready to sow as soon as they will drop from the stem at the touch of a finger.
Some stem-rooting lilies also produce little bulblets just below the surface of the soil. Sow them in a box or pot them singly in small pots. It is as well to collect these bulblets whether they are needed for propagation or not, as they attract slugs and are more likely to compete with the mother plant if left in place.
Leave lilies from seeds, scales and bulbils in the seed box as long as possible, say 12 months, and plant out in early autumn or spring just as with bought bulbs.
Some strong-growing lilies split into two or more bulbs nearly every year, and propagate themselves. It is often necessary to lift and replant them every four years or so. Since lilies need a year to recover from this kind of disturbance, move a quarter of the stock every year instead of having a grand move every four years with a lean following year. If the roots are very tangled, wash them clean in a bucket of water, and if there is still a tangle resolve it by a few strategic cuts with a sharp knife.