Mine usually didn't flower until later in the summer, even though when I buy them in May they might have a flower or 2.... be patient at least they are thriving

Mine almost never flower, and I think it has to do with lack of phosphorus. Most gardeners know that adding phosphorus promotes flowering in terrestrial plants, and that too much nitrogen can reduce flowering. I think the same thing is true for hyacinths.

If your pond is phosphate limited you might not get as many blooms as if it were nitrogen limited. My pond is phosphate limited, and I like it that way because algae doesn't do well in phosphate limited ponds.

I wouldn't recommend adding phosphate to induce hyacinth blooming because of the risk of inducing an algal bloom instead. Some people are lucky enough to have hyacinth blooms without algae, but I can't really tell you why.

All of the above is speculation and theory, so please take it with more than a few grains of salt. It is nothing more than my best guess.

My hyacinths just flowered today after a spell of hot weather, so it occurs to me that the answer might be water temperature. Hyacinths are tropical plants after all.

My pond normally runs cool, maxing out at around 75 degrees in hot weather, and my hyacinths don't usually bloom. I'm wondering if those that have hyacinths that bloom simply have warmer ponds.

For those of you that have hyacinths, please chime in with your water temperature and bloom status.

Hi
I'm in 10 florida so have lots of experience with heat lol. For me they usually don't bloom until the night temps are above 60 . Be sure they have LOTS of sun as well as heat. They seem to bloom in waves about 2 weeks apart..
gary

Mine flower if I crowd them. I take a piece of pond hosing and tape the ends together to form a ring. A piece of dental floss tucked under a rock to hold it in place and then fill with plants.

Gary, I'm going to count that as a point for the heat theory.

Cheryl, I try to crowd mine too, since I have always heard that hyacinths like that, but mine don't usually bloom. Crowding may be necessary for blooming, but I think something else may be necessary too. Do you know the temperature of your pond? Have you noticed any correlation between heat and blooming?

I know this is an old thread, but maybe it's time for an answer!

Calcium! Water hyacinth require somewhere around 5mg/L for proper reproduction (http://www.aquaticinvasions.net/2008/AI_2008_3_1_Tellez_etal.pdf). Try throwing in some crushed shells (can be bought at aquarium supply as crushed shell sand).