wisteria goin horizontal..

[Samala]

Well, I thought I would at least ask the question I've been pondering each time I stare at my tank the past two weeks. My wisteria is growing horizontal in the tank.. any ideas why? The leaves it puts out from each internode after I prune (cut the top and replant in the gravel) develop their own stems that grow horizontally across the tank and eventually sink roots into the substrate. I've read before that some stem plants will start to grow across the substrate in high light.. but I dont consider my tank high light at all. Just 2wpg 6500K T12's. Some pics are here (http://home.comcast.net/~slardizabal/krib2.html). Anywho I was hoping to be able to convince the wisteria to grow strictly vertically.. so I could get more of an aquascape going and be able to turn in the extra plants to the LFS or my friends. The tank is just about through its initial algae invasions and such so I'm planning on branching out into my planned design in the next few weeks. Ideas on cause and correction anyone?

Oooh.. details: 20gal long, 14/10 photoperiod, 40W 6500K, running for three months now. Dosing a little trace mix with iron and KNO3 and KPO4 to keep the plants going.
NO2/NH4 = 0
pH = 6.7
Conductivity = 380 uS
kH = 2
gH = 5
NO3 = ~5 ppm (I dose the KNO3 for a perceivable load near 10ppm but this never reads out, I imagine the plants are using it quite fast)
CO2 = 15 ppm

Thanks everyone!
>Sarah

[congealedmeat]

Mine did similar things in a 10 gallon with 2 40W incandescent lights(crappy walmart hood I got from someone).

[Swimfins]

Mine grows straight up, like its looking at the lights. Maybe your light is too low. Pic of mine attatched.

[tuchon35]

The same thing is happening to mine and i know it not because of lowlight. I have 192 watts over a 30. I thought it was growing horizontal because i had too much light. However, all of my other plants are growing straight up.
It is interesting that you brought it up. I see a lot of pictures where it grows straight up like a tree, where as mine looks a bushy shrub.

[Swimfins]

Maybe after top pruning it does this, my hygro polysperma began bushing out after I clipped some top pieces out.