Dig and Divide - Lilies for Free - Easy "How-to"
Look at your garden during late summer to decide which lilies might be overcrowded or have outgrown their allotted space and mark them before the flowers fade. After a few years, if a clump has many stems coming up around where the original bulbs was planted, only dig and divide when you see a reduced number of flowers. You might even wish to put a small marker where you wish them to be moved during summer, when a flower can be carried around to check color in potential locations.
Natural propagation is quite rewarding, you do nothing but water, weed and fertilize and nature provides a bountiful harvest, however it is best to wait until the beginning of fall when lily leaves are beginning to turn from green to yellow and the weather is beginning to cool. Assemble shovel, garden fork, labels and one or more buckets to keep the various varieties from being mixed. Alternatively, only digging and dividing one clump at a time works well also to keep things straight. A lesson learned from long ago, is that it is much easier to cover up the bulbs, than dig them up, so pace yourself. Lily bulbs should not be allowed to sit unprotected in the sun or for a length of time without soil for proper hydration. Aim for finishing the job within one day.
Carefully dig up the entire bulb, with the now-flowered stem attached. Use a garden hose and adjustable nozzle to wash off the soil and expose the mother bulb and the stem roots found between bulb and soil surface. Carefully cut the stem an inch above the big bulb using an old pair or pruners, serrated kitchen knife or carpet knife - something that can be sharpened, for without doubt, you will dull the blade on small pebbles or grit woven into the stem roots. Gently pull apart any fully formed bulbs that may have grown from the previous summer. If you clearly have two separate bulbs that come apart easily in your hands, congratulations, you've just doubled your money! Now remove the portion of stem that was above ground and discard in the trash. Do not compost old lily stems, compost piles generally do not heat up enough in winter to kill any fungus spores, such as Botrytis.
For Oriental or Trumpet bulbs, you should be left with a semi or solid stem portion, with perhaps a few white, yellow or pink bulblets showing between the old stem roots. Asiatic lilies may produce copious numbers of bulblets, perhaps more than you want, so only save the largest if your space is limited. If these new genetic clones of the Momma bulb are the size of a garbanzo bean and can be pulled off easily, then do just that. If they are rather small and firmly attached, then leave them attached to the old stem.
Large Bulblets: Plant any bulblet that is larger than a garbanzo into a garden trench about two inches deep. pace about in inch apart and when the soil freezes, mulch to protect them over winter. In spring, remove all but an inch of soil to allow them grow unhindered. Generally one single leaf will be produced. Do not allow the soil to dry out, but avoid soggy ground. At the end of summer, they should be touching one another, so after the soil cools, dig and space the yearlings about two inches apart.
Dug too early? - Underground stems only have tiny bulblets, the size of split peas, still attached to the stem and not showing any sign of roots? Do not try to remove the bulblets from the stem, but rather simply lay the entire section of stem, roots and all, on it's side in the 2 inch deep trench and proceed the same way. There are nutrients in the stem that will feed the newly developing bulblets until old stem, and roots, eventually decompose.