Sparky, I can't give advice for Florida, but good advice is usually available through the Florida Extension Service. The advice I read in their publications has always been dead on. Sandy

The hardiness of tropical waterlilies is pretty much poorly documented. The attitude among nursery folk and resellers is pretty much the sooner they kill them, the sooner they buy another one, over the years heat and cold tolerance information has been subject to errors of ommission, misleading and false misinformation as far as I can tell, quite a scam.

Many varieties of tuber are cold tolerant, coping with 40f waters. Colder than that and its pot luck which will cope, the night bloomers and the micrantha hybrids seem to be more durable than other hybrids

While the offset plant which is putting out the roots and shoots is likely to die in prolonged 40's water, the tubers that are formed are likely to survive, its always a good idea to find and save some tubers or vip plants indoors, easy enough to do.

Which is going to save wasting bucks replacing plants that are quite easy to protect indoors...

If you do lose a favourite variety through it being a weak, feeble or fickle variety, it's fairly easy to find a good un on ebay for $10 or so, rather than waste a lot more money for iffy plants from iffy resellers and nurseries

Hi
The only temps that would scare me are freezing lol.
They can survive down to that temp , . Lowering in the water will not help as unlike hardies they have no ability to go completely dormant.
Unless the water turns solid I wouldn'r worry even then I'd bet the tuber would resprout.
BTW . Two years ago I added a heating system keeping the water above 65 at all times not so much for the plants but the tropical fish. The water lily stopped growing anyway. It does continue to flower though about a third normal size pads also. Go figure ???
The most cold sensitive in my experience are the dwarf african types below 50 and they rot!! gary

Sparky,
I'm also in central FL z(9b)and I have never seen the need to sink lilies. It is the water temp that is important and even on the colder nights, that will remain substantially higher. We dipped to 38 last night and the water temp today in a small pond was still 60 and my ponds are shallow at 16".

There is no big mystery about the hardiness of tropical lilies...the key word is "tropical". At or near 50 water temp and the odds of losing them goes up to about 25% and climbs rapidly below that.

As for the drift to do with nursery folk...I am nursery folk and take strong exceptions to the unsubstantiated allegations made by adavis. A satisfied customer is a repeat customer and thriving lilies just strengthens the ponding "bug".

Granted there are disreputable nurseries/retailers both on ebay and in brick and morter shops. The best thing you can do to protect yourself if someone purports to be a 'grower' is ask if they are licensed and inspected by their state...the legitimate ones invariable are and every state requires a grower be licensed and inspected. And to insure you are getting the plant you are paying for and not a bogus seedling, ask if they sell the 'Truly Named' cultivars sanctioned by WGI certification program. Cheap ain't a bargain if the plant is not what you are wanting and a $10 bulb may sound like a deal until you lose precious growing time in a short season hoping you get it to bloom.

Thanks for everyone's input, it has really cleared my mind. Now I need more!!!Should I continue to fertilize the tropicals?

If your water is clear as a bell, there's no sign of algae and you have growing temperatures over 70°f you might try selectively feeding your favorites to see if it has a desirable impact.

With fertilisers being readily soluble you might notice an undesirable impact, algae bloom and other plants (weeds, lotus, taro) grow stronger in cooler temperatures hogging the fertility

You might find some varieties upchuck numbers of new offsets that choke the position in borderline temperature conditions, night bloomers and some prolific day bloom varieties tend to do that

As for sourcing plants, well, as the WGI certification has no facility for dna testing it would be difficult to consider the opinion of folk who have a history of self interested, mendacious, opinionated, despotic, autocratic, fatwah statements as any more accurate guide to identity as any other cranky source.

You might just as well go to the big box stores, for better prices and more reliable waterlilies. Granted, the labels are likely to be a muddle but you can always look up the pot luck varieties on the web if you look up the nursery website on the box (bad luck if it came from China)

As for resellers purveying such merchandise, well, how would the customer know if the plant has been cultivated to any standard relevant to the customer. Is the reseller competent to provide adequate cultivation information can be an amusing guessing game. Do they have any tangible credentials to know what they are blathering on about...

For all you know its been shipped in from Hawaii or China and will drop down dead or stunt for weeks with plant shock in your climate. It may be some shoddy feeble offset without even a reliable tuber formed... Is the variety a flash in the pan type that abysmally fails to tuber or has very fickle heat tolerance?

For all you know its been raised by iffy nursery folk or sourced from a hobbyist pond clearance who odds on have an iffy disregard for raising plants disease free (Plants from infected ponds consistently turning many varieties to mush)

Alas, the usda license only indicates what has been seen (apparently disease free) on a one day inspection. Which constitutes an iffy indicator as to what else might be shunted through any nursery through the rest of the year. A flimsy 'credential'

There is a huge variation in the hardiness of tropical waterlilies between the poorly documented flash in the pan new introductions (destined for oblivion) Victoria's and the Micrantha hybrids, should you lose a few flimsy ones its good to know a better choice at a better price is available on ebay, from independent collectors... folk who know them and grow them... Then there is a scattering of interesting nurseries which present exceptional choice and value such as Texas waterlilies, they do mail order.

Winter is a good time to get a couple of mail order catalogs, pencil in a few maybes, chat up a few collectors, get your dibbs in early on the good stuff... But do watch out for the vital cultivation tips and information, you don't want to end up with some fickle mophead which blooms turn to a shoddy cabbage the moment hot sun shines

No need to be stuck with iffy prices, flash in the pan plants, resellers, at all.

Hi
I'm located in Palm Beach county so the worst cold I deal with is frost but not even that every year. IME they will stop growing and lose pads but as soon as the water warmed they regrew. Of course frost will cause any plant to
lose leaves lol.
There would be no point in ferts when they are not actively growing . I hold off until Feb ,repot and add fert as soon as it actively starts growing again. I find they have way overgrown the pots anyway..
I think Craig has about the right idea on hardiness though I have never lost a plant to cold. Again frost is the worst I've experienced. gary

I am no good at all when it comes to lilies.I have too much shade to grow them reliably. I do read about them a lot (Here I am reading you, LOL). I have read they are sensitive to the light in addition to water temps. Could that be involved here? Sandy

Where a period of cooler weather and less daylight moves in tropical waterlilies tend to put up larger foliage which turn to mush when eventually photosynthesise is stopped by cold temperatures.

Night bloomers turn to mush early but leave reliable cold tolerant tubers behind, good timing is to winkle a few tubers out when the foliage is destroyed just in case the Winter is a bad one...

Cross your fingers your day bloom tropical waterlilies are good varieties at forming cold tolerant tubers if and when the top foliage is snuffed out

Some varieties are very reliable at forming reliable cold tolerant tubers which can cope with ice on the pond and 40's water. Red Cup, Wood's White Knight, Mrs. G.C. Hitchcock, Tina, Islamorada, St. Louis Gold, Lavender Lace, Miami Rose come to mind as more cold tolerant

Other varieties, are not.

You may find a large strong growing and blooming plant has formed a large log like tuber which has set no cold tolerant tubers, when the foliage is cold killed you might as well start looking for a replacement. Or drag the pot and plant into a safer place and hope to Winter it indoors keeping it over 55°f or so

Of course, any nursery worth their salt would provide such basic information as to tubering and known hardiness characteristics...

A little more info would be useful in offering suggestions. What are the lilies potted in if anything? And central FL is a large territory, I'm in south central (Hardee County)and may be a touch warmer, if say, you are at the northern limits. Is the pond dug or above ground, lined or mud?

But even without the add'l info...your lilies will tell you what they want and if they are still growing, they will want fertilizer, though I cut back from weekly during the peak August/September growing time, to monthly in the cool weather and even here most bloom year round.

With temps at or slightly below marginally acceptable levels for tropicals, cell metabolism in a vigorously growing plants produces enough heat to maintain some growth and without supplemental feeding may result in the tuber being depleted and the plant lost. As Gary correctly pointed out, the plants itself and especially the pads, will shrink in size as cell metabolism is directly dependent on a minimal temp. The pads will definitely 'not' increase in size in cool temps as the reduced metabolism cannot support it. And as tropicals are just that, they have not evolved the genetic abilility to form cold tolerant tubers. At or near temps of fifty, the cells should be able to survive, but not produce growth, but much below that and odds are tubers will succumb. Long way of saying....as long as your lilies are growing, feed them, albeit sparingly.

If you decide to find a new supplier, there are good and bad both on line and in traditional venues and one way to sort the good from the bad is ask questions...primarily are you a registered, licensed grower. No grower knows it all and being inspected adds an added pair of specially trained eyes to spot potential problems....and it is done on a state level, not by the USDA.... Inspections and licensing are for your protection and a legitimate grower is glad to undergo any inconvenience to insure he is providing his customer with a healthy plant. To ignore the state requirements designed to protect the consumer, in my mind, shows a total disregard for the customer.

More and more growers/retailers are taking the extra step and offering Truly Named lilies...lilies guaranteed to be true to type.... and while no law requires it, it is just that extra step that shows the grower takes pride in their product and cares about the customer, so it is a telling question to ask a prospective suppler. And no DNA tests are necessary. As cultivars have to be vegetatively cloned, it can be done by provenance which is simply following the clone back to a provable source.