Reasons to avoid planting "Pre-cooled" Lily Bulbs in Late Summer and Early Fall.

Usually just before frost or a chance of snow, we receive a few cries for help regarding newly planted

lily bulbs (obtained elsewhere) that are emerging too early.  For the benefit of new lily gardeners, or those considering "early planting", a recent email brought up a very good question.

Frosted leaves droop down.

“Sorry for a dumb follow-up question, but it appears you are saying lily bulbs should not be "pre-cooled" for shipping in the fall?  Maybe it is not necessary to pre-cool in the late fall, since they are being planted in the ground that is already cooled?  But if the bulb shipped in the fall is pre-cooled, and then planted in the cool ground, is that a problem?”

Sorry, the answer is "Yes", because it indeed is a problem for most areas.  Hopefully, this little article will help someone make a good decision on planting lilies this fall.  First, and foremost, it is helpful to understand what is meant by the description "pre-cooled and what pitfalls will be encountered in  areas that have heavy frost or snow during the early winter months.

1. Definition of the terms: "Pre-cooled", "Pre-chilled",  "Ready to Grow" etc.

These terms are used to describe lily bulbs that were prepared for out-of-season growth by providing an artificial winter in cold storage.  They are packed in wet peat and slowly cooled until the medium is frozen solid and the bulbs are lightly frozen.  Upon warming, even for a few days, those bulbs will immediately begin growing sprouts – exactly as they were programmed to do. 

"Pre-cooled" is a greenhouse industry buzz word – which really means "previously frozen", and is used in the same manner as your neighborhood grocery store, advertising shrimp or fish "previously frozen".  These stored bulbs may be in the freezers anywhere from two months to two years before being sold, but without actually cutting a bulb open to inspect the interior sprout, it is hard to tell from the outside how long they have been stored and if the sprout has died.

 

2. "Pre-cooled" bulbs are intended for a very narrow segment of commercial growers

The process of artificial cooling was originally intended for greenhouses and for companies in tropical climates growing cut flowers outdoors, who may not experience enough winter chilling to vernalize bulbs naturally.  If a lily bulb has not received enough cold treatment, either it will stay dormant (not emerge), or will grow a stem without any flowers (blind stem). 

Bulbs harvested in fall, and kept in commercial cold storage until a greenhouse operator is ready to plant in the middle of winter, are triggered to grow stems when "thawed".  This is good for a climate controlled greenhouse, because the owner knows exactly how many days until the flowers (and entire stems) are ready to be picked, and so can adjust planting week by week to optomize sales.  Commercial greenhouse growers simply discard bulbs after cutting, no matter what the season or the climate. Forced bulbs have expended all their stored energy growing a stem and flowers, and there are no leaves left from cutting to fatten them up for next year, plus a new crop is waiting to be planted in the same spot.

3. Difficulties in Temperate and Severe Climates, without a heated greenhouse

In areas with a definite winter (temperatures below about 38 degrees F), planting in “cool ground” will not stop cold-treated lilies from beginning to sprout, because once growth has been triggered they cannot be forced back into dormancy.   

Heaping a thick mulch over the top of untimely sprouts will not helpful, because the warm surroundings just encourages more active growth, nor is keeping thawed bulbs in the fridge a solution because they will continue to grow, causing sprouts to curl around inside a bag.  Attempting to home-freeze lily bulbs that have warmed up will only result in a bag of soggy mush; think of an onion that has been frozen whole, the texture would be the same.

"Pre-cooled" lilies planted in the garden in late summer or early fall in warm Southern States (USDA Zone 9 and above) could make it to budding stage in November/December (average 100 days, planting to flower for most Orientals), but only if the nights stay around 55 degrees.  Unfortunately, just a single hard frost can destroy both stem and flowers.  If bulbs are able to flower because the weather has not been freezing or they were planted in a greenhouse, they will still need at least another month of warmer temperatures to mature the foliage.

Natural Cycle Bulbs are best for Fall planting

Bulbs fresh dug in fall and immediately planted, for the most part, require at least 8 to 10 weeks of cold before they will start to grow, and will simply wait underground until the soil gradually warms before sending up a stem.  They are on a natural cycle that tolerates cooling underground, because this semi-dormant stage usually involves growing new roots in preparation for milder weather in spring.

"Pre-cooled" are for Spring Planting in any region

Lily bulbs straight from the cooler in late February to April are not a problem; they can be planted  as soon as the soil thaws and light frosts above ground will do no harm, because they are waking up in tune with spring.  They'll bloom and have the rest of the summer to mature their foliage.   For example, a lily bulbs the size of a tangerine will lose about 80% of its mass just coming into flower, shrinking to about to the size of a walnut before it then begins rebuilding the bulb following bloom.  They need all their leaves to build that bulb back up again for the next year's bloom and appreciate another shot of fertilizer then as well. 

The Final Advice

If you live in an area where winter temperatures are below 38 degrees F. for more than a week or two, then either plant natural cycle bulbs – harvested a few weeks prior to delivery in the fall – or wait to plant lily bulbs in the spring, that will promptly begin to sprout as your local weather begins to warm.

 (Also see from December 9, 2011 "Warning about "pre-cooled" lily bulbs in Fall/Winter")

UPDATE: On Facebook this morning (8.10.13) a question was asked about how to "tell" whether or not bulbs offered are fresh, so here is the reply:

"Ask questions!  In general, companies (brokers) who supply greenhouses will say that their bulbs are cold treated, which is what the cut flower growers require.  If they were not already given the required amount of chilling, then they would not grow under glass properly, which is why that market exists.  The down side is brokers also will sell to just about anyone looking for a full case of bulbs and this is where the problem starts.  Now you are dealing with a "jobber", someone that simply buys to resell.  Simply put, they are not the producers but are simply in the business of selling "widgets". 

Asiatic lilies grown in the East and Midwest mature their stems earlier than on the West Coast where we live, so someone who actually is a grower - not a reseller or "jobber" buying from a broker - may be able to supply some bulbs in early September, but I do not know of any farmer who can supply fresh-dug Oriental lilies at that same time without compromising their growth, because they need time to mature stems.  So, in general, Oriental and Orienpet lilies on the market "too soon" in fall may be selling old stock from the freezers. 

I've heard of vendors selling lily bulbs at county fairs or other events in August, telling people that the long sprouts mean “they are alive”, which indicates they were out of a cooler crate, not a field.   I once heard that at an event myself at a late spring show, and just stared at the person in disbelief, until they saw my own vendor badge for B&D Lilies, and clammed up. "