Trop. care, repotting and root-pruning

15 years ago

I've done a search, but I'm finding conflicting information, both here and on the internet in general so thought I'd try to just ask.

I have a tropical hibiscus I bought about 3-4 years ago at a grocery store in about a gallon size pot. I potted it up two years ago into a 3 to 4 gallon pot, because it seemed to be struggling and it was better, but last year it was pretty scraggly so I cut it back fairly severly last winter (early December). I keep it in the house in winter and when warm enough open my only sunny door to give it light. The sun beating down on my south-facing storm door gets pretty warm. The temp where the plant is stays about 65-70 degrees. Now it has a few leaves, but doesn't seem to be growing any new branches.

I am thinking of repotting it, that perhaps it is root-bound? I haven't checked yet but it just doesn't seem to be doing well. Here is my problem...

I have read that hib. like being root-bound. I've also read that they don't. I don't know whether I should treat it like a tree and root-prune it, or just repot it. I don't think it's in the best potting medium and am planning on switching it to a faster-draining soiless mix - but to do that, don't I need to take it down to bare roots and get rid of all the old soil? Finally, what time of year do you do something like that to a tropical that isn't dormant? I don't want to kill it with kindness.

Thanks in advance to anyone who can give me more guidance!

Comments (2)

tapla (mid-Michigan, USDA z5b-6a)
15 years ago
Hi, Alys. I got your message, as you can see. ;o)

Technically, no plant likes to be root-bound. If it did, Mother Nature would have the roots growing in cute, tight little balls - maybe cubes. ;o) WE sometimes prefer to manipulate plants into blooming by growing them tight, or we might allow plants' roots to get tight in a reduced volume of soil for plants that don't like wet feet and 'need' a reduced volume of soil so it dries quickly to a favorable moisture level.

Growth is measured by the increase in biomass of the plant; and in every case, tight roots diminish the potential for increased mass. Plus, in Hibiscus, tight roots inhibit both branch extension and blooming. It also tends to make the leaves smaller and grow in 'tufts' at the ends of branches.

The root systems are very vigorous, so the plant will need root-pruning/repotting every year or every other year to keep it growing at close to its potential vigor. Because they need repotting so frequently, there is no need to go to the gritty soils that last for several growth cycles. I know you're familiar with the 5:1:1 mix, and that is what I use on Hibiscus. It works well.

I don't frequent this forum too often, so I don't know what the general consensus here is about fertilizing, but they're somewhat unusual. They need average amounts of N, very little P, and lots of K. Important - NEVER use fertilizer formulas with the middle number more than 1/3 that of N, - NO 'bloom-booster' blends. A fertilizer in the 3:1:4 ratio would be good, but they're hard to find w/o paying the long dollar for "Hibiscus Fertilizer". Instead, when you repot, add a Tbsp of potash for ever gallon of soil. This will raise the K levels and make the common Miracle-Gro fertilizers in the 3:1:2 ratios (24-8-16 granular soluble or 12-4-8 liquid) perfect. Alternately, get some Dyna-Gro ProTeKt 0-0-3 and include some in the fertilizer solution every time you fertilize.

Do your repotting & cutting back early in the year - about the time you can put the plants outdoors and leave them there.

I hope that answered everything.

Take care, Alys.

Al
lilion
Original Author
15 years ago
Thanks Al! You are a treasure! Looks like I still have time to repot this plant since it won't go outside until May usually.

Potash. Something else I need to find now! LOL!