I have been doing a bit of research on lily health and storing the bulbs (corms) over winter, as I am keen to ensure my Lilium Regale will be good next year.
I have been feeding mine weekly with liquid tomato feed, which has worked well.
I have also been on patrol for lily beetle. These are about the size of a ladybird, slightly more oval in shape and a bright orangey red. They are easily crushed between thumb and forefinger.
The real pests are their young. The adults attach the grubs (about the size of a large comma) to the underside of the lily leaves, and then coat them in excrement.
The excrement then provides the grub with a coating that allows it to slip down the plant into the soil, where is feasts on the lily bulb over-winter: effectively stunting or killing the plant. The grubs can by crushed, or put into your brown in or landfill. I’d advise against composting, just in case….
Storing Bulbs over Winter
Until the autumn keep feeding the lilies with a high nitrogen feed (e.g. liquid tomato feed)
In mid -September cut the stems down to 3 ~ 4″ and remove all the leaves.
Keep feeding until the 1st week in November, when you lift them. Clean the bulbs as best you can leaving the roots intact. Then transfer them to a store.
To create a store either prepare a large poly bag by punctuating it with vent holes or enlist an open weave plastic box. Line the bottom of the bag or box with stones or gravel to ensure good drainage. Then half fill the container with compost, place the bulbs on this and then cover them to a good depth with compost. The strong warning I have read is not to use garden soil, rather compost. To this end the growbags on sale in the Allotment Shop would be ideal! And £3 at pop, a snip!
Store in a cool dry place. I planted mine out in pots in May of this year and had a spectacular show in late June and most of July.