Fertilize lilies 2-3 times during the active growing season.

I recommend feeding them when they first stick their heads above ground in early spring. Then repeat just as flower buds form (or the first flower opens). You can give another feeding some 4-6 weeks later, but don't wait to too late in fall as too much nitrogen late in the season can rot the bulbs in winter.

I would personally recommend waiting until next spring to feed them.

However, as regular maintenance you could:
- deadhead spent flowers before seed heads are created
- leave the flower stems with leaves to grow on (do not cut)
- mulch the area in winter to avoid heaving and dehydration. A mulched area gives better results in spring, too.

If you wish to divide the lilies, then fall is a great time just as the stems die back. Dig the bulbs and seperate the big from the small. Replant big bulbs (1.5" diameter or wider) about 1 per sq foot, and smaller bulbs can be planted 2-3 per sq foot. Cover with 6-8" of soil. Always plant in well draining soil.

Good luck.

Thanks so much for the concise and thorough run down on how and when to accomplish all that needs to be done.

Aside from those miserable lily leaf beetles I think lilies are just about perfect, and deserving of more attention than I've given them. They were gorgeous this year, BTW, and I will have to add to the collection with some that bloom a bit later.