Protect your bulbs from "freeze-thaw" conditions and excessive moisture this winter.
Potted lily bulbs need to be insulated from rapid freezing and thawing over winter. Failure to protect bulbs during temperature swings, combined with too much rainfall, may result in a total loss. Although your lilies can be perfectly hardy in the garden where ground temperatures fall and rise slowly over many days, unprotected pots can freeze solid within one hour.
We like using the double-walled containers, shown in photo and sold by Costco in spring for all of our bulbs, not just the lilies. If stored under our porch roof and kept on the dry side the lilies winter over just fine down to zero degrees. In colder areas, strategies may include packing pots tight against one another and surrounding them in sawdust or hay after the ground freezes, placing them into a root cellar, or wrapping the pots in fiberglass insulation and storing them in an unheated garage .
Do not bury pots in the ground without also covering them with plastic or a board because they will not be able to drain excess water properly, especially in early spring. In the ground, the drain holes will rapidly become plugged and the pots will act as a sump, catching rather than draining away excess moisture. It is the sudden and deep freeze/thaw cycles combined with saturated soil that causes damage to lily bulbs. If potted lilies are caught outdoors and are frozen solid, try keeping them frozen with mulch or insulation for the remainder of winter, allowing pots to naturally and slowly thaw in spring. One of our Alaska customers has good results with placing her containers under the house in the crawl space; the small amount of heat from above keeps the lilies from a deep freeze.
In the Pacific Northwest, winter comes and goes; we might be sunny and warm one day and frozen the next with rain, sleet, snow or hail in between. The most important thing you can do with varying weather patterns in a maritime climate is to not allow containerized lily bulbs to become saturated. Simply placing pots under an overhang, deck or covered porch out of direct sun is sufficient for most areas that rarely go below 15 degrees F. in winter. Placing pots on their sides on the north side of a shed or garage also works rather well to protect them from winter rain in milder climates, just remember to set them upright when sprouts emerge. However, this only works with established potted lilies because the stem roots just under the surface keeps the soil from escaping; don’t try it with newly potted bulbs! We’ve also had good luck with simply mounding dry peat on top of large half whiskey barrels – the dry peat tends to first repel - then absorb - excessive rainwater between storms. In spring we removed the peat when lilies first start to emerge in the garden. You might have a few pale white shoots, but they will quickly start to turn pink after a few days of light.
Please remember that our guarantee for winter hardiness does not cover potted lilies, so be sure to protect your lovely lilies over winter or transplant them into the garden this fall.
P.S. The photograph shows the trial conducted this summer on the Intermediate height Gladiolus we are offering next spring in the printed catalog and on-line. Shorter growing than the old fashioned types, they are nice in large pots for portable color or planted in the garden.