I got a couple of wasabi seedlings nearly three years ago and planted them in large pots. Last weekend I dug one up to eat and was pretty disappointed with how large the main stem was. However there were dozens (25 good ones that I replanted) of offshoots growing, some of which were quite large and had lots of leaves and such.
My thinking is that the main stem grew a lot less because of all the offshoots growing at the same time. So my question is; is there some way that I can encourage the main stem to grow instead of it producing so many offshoots?
I could probably repot it more often, like every 6 months or so and remove any offshoots at that time, but that will be pretty tedious and probably not ideal for the plant to be shocked so much, so often. Could I just cut off any leaves which I think are coming from an offshoot? Would planting it in a smaller pot help, maybe plant it in a toilet roll tube or similar to avoid them being able to grow from the side? Anything else I can do? Different sun/water/nutrients?
Here's a picture of the main stem:
And the pile of offshoots:
