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Hygrophila polysperma


Derek

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Hi Paul,

I was interested to see the photo on your web site showing H.polysperma flowering. I was always under the impression that this plant had never been known to flower. I soon found out I was wrong. In their book, Aquarium plants their identification, cultivation and ecology (1977) Rataj & Hormeman say

Hygrophila polysperma

“Specimens cultivated under this name for some forty to fifty years have never flowered. Their identity is therefore uncertain. Among the imported plants of the last few years have appeared plants similar in the submersed form, but in the emersed form with top leaves clearly hairy; the plants flower easily and regularly. These flowering plants have been reliably determined without doubt to be H. polysperma. Is the plant cultivated for so many years in aquariums under the name H. polysperma only a non-flowering form of this species? Or is it a question of another species? This problem cannot be solved until we are able to make the sterile plants flower.”

None of the plants of H.polysperma that I have seen growing emersed have had hairy leaves. In the Wellington region it appears that the “non-hairy” form is present but not the “hairy” form. I’ll have to find a better way of naming them.:???: It would be interesting to see if these two forms are distributed differently around NZ. If members could please post their location and form(s) of H.polysperma , I will try to collate and post the results

Paul, do you have both forms?

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Derek

I personally don't have the Hygrophila polysperma anymore :sad: but from memory mine was the 'non-hairy type' but then again I never grew it emersed.

Paul, can I place a copy of your picture of Hygrophila polysperma on this site for easy reference (credited of course, with link)

Derek, could you take some to clubnight on Thursday, I can bring a digital camera!

Pauls webpage with the flowering Hygrophila polysperma is here

[ This message was edited by: Cees on 2001-05-07 06:50 ]

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Hi Derek

Good question I am pleased you have pointed it out.

I consider them to be the same species!

I had mine growing submersed for at least 10 years with never a sign of it wanting to grow emerged growth. Then I decided to grow it emerged to try and flower it.

I set up a big clump in only very shallow water so that if it wanted to grow it had no option other than to grow out of water.

This was done in my fish room under flro lighting and with a tight fitting cover glass, It did start to grow emerged but not very well and with no signs of flowering.

I left it like this for about a year, At that stage I decided to try it out in my tropical glass house so that it received natural sunlight and was also exposed to seasonal changes in lighting spectrums and intensities from the sun it self as well as my own controlled lighting.

It started to grow really fast but still no sign of flowering or hairy growth on the emerged stems.

I then installed HID lighting in the glass house in the form of a 400watt metal halide and also a 400watt high pressure sodium light.

I run this lighting for 18 hours a day over the summer months and cut it back to 15hours over the winter months.

This plant grows very well and fast during the summer when exposed to 18hrs of light and temps of 25 to 30 deg C.

But when the lighting duration is dropped down to 15 hours a day and the temps drop down to 20 to 25 degC it FLOWERS and continues to do so over the and winter months only. And then produces fast vegetive growth through out the summer months. It is only the stems that are flowering that show hairs on the stems as you can see in the picture.

PolyFlow.JPG

So as you can see from my playing around with this species what I believe triggers flowering is

  • The plant is forced to grow emerged.
  • It must have the seasonal changes in temperature
  • It needs seasonal changes in
    1. lighting duration
    2. light spectrum.

A plant can be controlled easily with lighting. For fast vegetative growth the lighting needs to be about 6500 to 8000k ie Lots of blue light and have a maximum duration that can be as high as 20hrs of light per day.  To trigger plants to flower or reproduce via runners etc the lighting needs to be 3000k to 6500k ie lots of red light and a duration of 10 to 12hrs per day.

All of this stands very well with most plants and I use several of the above changes to flower my plants at will.

With the  variegated form it is unknown if it is a virus or a genetic hybrid that causes the white veins, I tend to think that is a true hybrid or another species altogether because of the different growth habits.

I do sell a lot of plants to the Wellington area so my Hygrophilia polysperma is in you region and at this time of year you might see the flowers themselves if I've just delivered some stock to one of the retailers.

Anyway I hope this note is usefull to you.:smile: I am going to be away for a couple of weeks so I wont be able to help you out on any questions you may have over the next two weeks, I am off to sun my self on the sunshine coast of Qeensland :cool:

[ This message was edited by: Paul on 2001-05-07 07:08 ]

[ This message was edited by: Paul on 2001-05-07 07:54 ]

[ This message was edited by: Paul on 2001-05-07 07:57 ]

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