what a refreshingly astute question; thank you for asking it here.how many of you follow 'bonsai tactics' like judicious trimming
this is actually a subject I have been pondering and I may have
stumbled over something that many could have noticed, but few
ever discuss as a method of managing plant growth.
Hydrophila polysperma "Sunset" aka "Rosanervig" is a gorgeous
pink leaf plant, yet many avoid it because it grows like a weed.
but what if I told you there is a way to not only slow it's growth
but even make the leaves come in smaller and denser than usual?
here's how it works. take a 4x4" spot and plant 9 short stems
within an inch of each other and an inch away from other plants.
O O O O O
O X X X O O=Other
O X X X O
O X X X O X=Sunset
O O O O O
now leave the Sunset to grow fast into a tall rambling bush.
after a few weeks, you will notice the top leaves shading the
bottom leaves, and the bottom leaves grow in small and slow.
now here's the tricky part; look carefully, and you'll notice a
spot on each stem where the leaves shift from small to large.
Cut the large leaf section of the stems, uncovering the small.
you will be left with nice neat bush of small slow growing Sunset!
somehow, the small leaves remember to keep small because they
were deprived of light by the upper leaves - that are no longer there.
every once in a while, a stem or two will sprout a fast large
leaf off shoot, give it an extra week to grow out, then cut it,
the same way, back to the small growth leaves on that stem.
maintain this type of Bonsai trimming vigilance, and you will be
rewarded with an gorgeous well behaved bush of Sunset leaves.
This approach also works with many other fast growing plants,
such as Hygrophila difformis aka Wisteria. It will probably work
with many plants where fast growing leaves shade and stunt
the smaller up and coming leaves under them on the same stem.