Thanks for stopping by! Hmm It's a combination of trimming off the tops to a height that I want, and pre-emptively pinching/cutting off tips that start to grow towards a direction that I don't want it spreading to. For L. sp red, the rooted stem is quite strong if its healthy, and the top can be trimmed off repeated; side shoots sprout fast. The whole bunch in the 47g are branches that come off from about 4 mother stems that root into the substrate. I felt that the trimming for the L. sp red is actually poorly done in the pics compared to the L. Arcuata; it can be contoured in a very exact manner, but I must have missed it when I took this set of pics.
About every 4 months I allow the current batch to grow longer, then do a replanting of tops (where the top node to bottom has no branching).
I think that trimming and allowing side shoots to sprout allows more self-organization (because the plant will grow in a way that doesn't shade itself that much), it makes for a neater, denser bush. Replanting tops kinda resets the plant form to be competitive against surrounding plants. In the search for neater tanks I've been doing alot more pruning and almost no replanting for tops (until after many months). Just a theory based on observation though. It seems to apply to other plants as well. The effect is most apparent in the Ludwigia arcuata (orange background bush); where the dense bush must be achieved through trimming and allowing the side shoots to self-organize to fill up the space. If I just grabbed a bunch of them and planted them side by side, they'll grow in a vertical competitive manner instead of spreading out. I've been wanting to do a video to demonstrate this (because people don't seem to talk about it much) , so I've replanted the entire middle of the tank (start from scratch with sparse stems) and pruned it into a bush like in the pics over the past few weeks. The bushes have grown back in over the past month though, so in a week or so I'll finish my video.
Using an older set of pics to illustrate:
When background stems are planted individually, abeit densely... they each struggle to outgrow the neighbour:
After allowing it to grow out further, before doing a very aggressive trim:
After it has grown out; with self-organization with respect to neighbouring plants:
I know you were asking about L. sp red. But the pruning technique is similar, except that Sp red spreads sideways quite abit more than L. Arcuata. I'm thinking of trying a large pruned sp. Red background for the next tank though Hmm...