A very common inquiry from gardeners has to do with storing bulbs such as Canna and Calla Lilies. These are are valuable bulbs and a category of plant that is next to impossible to purchase from organic sources; by saving your own plants you can multiply your stock and support ecological stewardship by avoiding the re-purchase of chemical-intensive products... not to mention save yourself money!
Here are some tips for best success wintering your warm climate bulbs:
1) Allow plants to die-back naturally before storing. In most cases the best way to know that your non-hardy bulbs are ready to be cut back and stored is to let them have light frost. The on-set of cooler fall weather definitely flips the switch in the right direction... but frost is the finishing touch. Clues that plants are ready to be cut back and stored include significant yellowing and die back of the foliage. At this point in the season (late October) all bulbs can be prepared for storage; thinking ahead to future seasons the tip is: avoid digging these out too early as non-dormant bulbs do not store so well.
2) Dig gently. The skin on the outside of bulbs is an important protective layer that allows them to be stored successfully. Nicks and scratches provide an entry point for bacteria and fungus that undermine the viability of the bulb. Allow lots of space around the bulb when digging; once the bulb is fairly loose fingers might be the best digging tool!
3) Some bulbs require a period to cure. Species such as Gladiolus, Calla Lilies and Crocosima grow from corms (versus tubers) and these should be set out in a warm well ventilated location for 2 - 3 weeks before going into storage (much like onions and garlic). In our region curing is typically done indoors as the exposed bulbs cannot tolerate freezing. Curing is not required for Cannas and other tuberous bulbs.
4) Do a light cleaning before storage. This step actually comes before curing on those varieties that require curing. Any excess soil can be gently shaken off as a first step; part two involves a light rinse to remove stuck-on mud. Avoid using a vegetable brush or other abrasive tool as this can damage the bulb.
5) After cleaning (and curing if required) excess roots and top shoots can be cut back. Crop the roots close to the bulb or tuber and cut tops to an inch or less.
6) Store the bulbs in a loose media such as perlite or vermiculite. The goal is to keep the bulbs stable and dry through the winter; other materials such as dry coco-earth or sawdust can also be used. Layer the bulbs and space them out so as to avoid touching. Do not bother storing any plant material that is shrivelled or otherwise looking less than pristine.
Bulbs can be dipped in ground cinnamon ahead of storage; this is a very effective way to prevent mould or rot.
7) The bulbs can be stored in a location that is dry and maintains an even temperature above freezing. The ideal temperature is around 10˙C (crawl space; heated garage; sometimes the basement). Check the bulbs every month or so to identify and remove any that are spoiling (leaving these can cause a bunch to go bad).
8) Don't forget to label! It is too easy to forget what is what come spring planting time.
As an alternative to the above method gardeners have the option of simply leaving non-hardy bulbs in pots and letting them die back without digging them out (obviously only works if the plants are potted rather than in the garden). There is a nice advantage to this method... it is so easy!
That said, the pots need to be near light during dormancy so that the bulbs can wake-up on their terms when they are ready. I also like to water about once per month to ensure the soil and roots do not dry out excessively. Once new growth appears regular watering and feeding (general purpose organic or bloom booster organic) regularly.