tropical hibiscus not blooming

dtillyer(Manhattan)August 4, 2012

I've got two nice hibiscus (hibiscii?) that are not flowering. I bought them

four summers ago at the local supermarket. They were two feet tall then.

I've brought them inside every winter (I live in upstate New York) and they

have reached about 8 feet tall now. However, I have had one (only one)

flower on them this year. The foliage is beautiful. There is lots and lots

of new growth. We had a tough drought, but there's plenty of rain now.

What gives. They're beautiful, but my hummingbirds are pretty ticked off!

David Tillyer

Montgomery, New York

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tapla (mid-MI z5b-6a)

If you haven't repotted them regularly (as opposed to potting up), and especially if you haven't even potted up, look there first. It could also be the fertilizer. Hibiscus wants minimal amounts of P, so bloom boosters are a very poor choice. I bet, if you post a picture, it will show almost all the foliage concentrated near apices. If so, it needs repotting, not just potting up.

Al

    Bookmark   August 6, 2012 at 2:24PM
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robitaillenancy1(zone 5)

Try a fish fertilizer of one with high second number.

Nancy

    Bookmark   August 7, 2012 at 2:42PM
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robitaillenancy1(zone 5)

Sorry, the above message should read: fertilizer with high 3rd number.

I use Acadie Algue Marine Seaweed 0.03-0.03-4. It is expensive--$20.00.

Nancy

    Bookmark   August 7, 2012 at 2:59PM
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dtillyer(Manhattan)

Hi Al. I potted up this spring. I put them in slightly larger pots with some compost and some potting soil. The foliage has really taken off this summer,
so I guess the roots have too. Maybe I should pot up again. I assume the difference between repotting and potting up is that potting up simply means a larger pot, whereas repotting is just refreshing the soil in the same pot.

As to fertilizing, I usually just use MiracleGro, and feed the hibiscus when I feed everyone else in the garden.

The new growth is near the apices (top of the plant). You're right Al. I wonder if I should prune the tops. David

    Bookmark   August 11, 2012 at 10:35AM
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tapla (mid-MI z5b-6a)

I'll leave a link to something I wrote about maintaining trees in containers over the long term. It addresses the difference between repotting and potting up, ant the impact it has on plants over the long term. It applies as much to shrubs and other plant material with branching root systems, which of course includes Hibiscus, as it does to trees. See the link below.

Also, MG makes several formulations. You should avoid 20-20-20 and other 1:1:1 ratio fertilizers for Hibiscus because it's impossible to supply an adequate amount of N w/o over-fertilizing with P, and Hibiscus rebels at even relatively small amounts of excess P in the soil solution. Use their 24-8-16 or 12-4-8 instead. Both of those fertilizers have a 3:1:2 ratio. If you really want to fine tune your fertilizer, to the Miracle-Gro 24-8-16 or 12-4-8 solution, add about 1/2 tsp of potash (Espoma sells it in small bags) to each gallon of fertilizer solution. You'll end up fertilizing in something near a 3:1:3 ratio, which is very close to ideal for Hibiscus.

If there is anything you didn't understand in what I said (fertilizer ratios vs %s can be confusing), let me know and I'll explain.

If it was my plant, I would saw the bottom 1/3 of the root mass off, then cut deep vertical slits in the root ball with a utility knife (new blade) at 3-4" intervals, knock a little soil off the sides of the root mass, and pot up for now. Next spring, before the plant starts to grow in earnest, I would do the full repot as explained in the link below. You'll be amazed at the difference it makes in growth, vitality, and the plant's ability to bloom abundantly ..... ESPECIALLY if you follow the fertilizer advice.

Best luck!!

Al

Here is a link that might be useful: Click me for much more info

    Bookmark   August 11, 2012 at 12:06PM
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dtillyer(Manhattan)

Thanks, Al.
I think I'll try to follow your advice to the letter.
Very useful. David

    Bookmark   August 14, 2012 at 8:53AM
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