Grow 545: Hibiscus, redbud, winter

Early Winter!

Garden flowers can be visually attractive right through winter

Dear Janet,

I have a lovely perennial Hibiscus bush. The flowers are huge and beautiful, however I am having a problem trying to germinate the seeds. Last spring I planted them in a flower pot and kept them well watered. Nothing came up!! I planted some in the ground and kept those well watered. Nothing came up but weeds. Now I have a new crop of seeds for next spring. Please tell me how to store them, plus how to get them to germinate next spring.

Does my established bush need some kind of fertilizer?


Dear L.M.,

Hardy hibiscus seed will germinate in warm, 70 degree soil if you sow it as soon as it's gathered. You should see about a 50% germination rate over 2 to 4 weeks.

The trouble with sowing seeds of this late summer blooming species when it's fresh is that by the time the pods are brown and the seed is ripe, it's October. You must sow the seed indoors to provide that 2 to 4 weeks of 70 degrees. Then you would have to raise the seedlings as houseplants that first winter, since seedlings, hardy species or not, can't be moved from indoors to outdoors in November and be expected to survive.

So clean the seed of chaff, put it in an envelope and store it until spring at 40 degrees -- refrigerator temperature. Then sow it next spring.

Stored cool, it should have the same germination rate as fresh seed. If stored at room temperature, that rate will fall way off. This is often the case with seeds of late blooming native perennials. They "expect" to be cool after ripening.

As a swamp native, the hardy perennial Hibiscus moscheutos appreciates rich soil. You can use almost any type of fertilizer. Or just keep adding compost to simulate the sludge deposits that can be expected at swamp edge as this plant does what wetland plants do, which is to slow down runoff water and filter out the nutrients that water picked up along the way.

I have some hibiscus in my own yard that have managed very well on compost alone for twenty years, as I rarely get around to buying fertilizer for my plants. Being a professional gardener means one's own garden becomes like the shoemaker's kids' feet! I give the plants lots of compost by adding four to six inches of raw leaves every fall which break down over winter and the next year.

So use any kind of a fertilizer in May as growth begins. At clients' gardens I use slow release poultry manure or Osmocote so that nutrients become available to the roots over a long period of time.


Dear Janet,

My redbud began to bud up last spring but the ice storm in April killed it. In June I noticed a few leaves sprouting from the base of the tree. Now I have a huge bush growing up from the bottom. It's several feet across and about four feet tall. What should I do with it? Wait until spring to see what happens or prune it back now?


Dear L.B.,

Isn't Nature grand? The top died but some dormant buds at the base of the trunk survived and began to grow. Given all the energy of roots that had been part of a big tree, those buds grew at the fast rate you describe.

Now the roots aren't so thick with starch -- stored energy -- as they were in spring, however. Where once they had thousands of leaves making starch for them, they had fewer this year. So let the roots take all they can from this year's foliage. Most of the leaves' excess energy was socked away in the roots during the growing season but even now, every day that it's above freezing, starch may still be working its way down through the branches to the roots.

Let that happen. Then, on the first of April next year before new leaf growth begins, prune off all the branches except those you want to become the new trunk or trunks. As the roots begin transferring the energy back to the top, it will go into only the buds on branches you've decided to keep and you'll have a "new" tree in short order.

Short reports

Seniors should check for a community Chore Referral service.

C.K. of The Senior Alliance wrote in response to the question from A.H., about where an older gardener might find garden help, "We have a Chore Referral program for seniors who are looking for assistance doing home maintenance tasks by giving them the names of independent workers, who have been asked to charge reasonable fees. Homeowners then make their own arrangements for the work and payment of services. Many communities have such a Chore Referrral list that could be obtained  by calling the local senior center."


Green thumbs up

to using a magnifier now to check leaves of pest-prone indoor plants. If winter's short days and lower light are weakening the plant, its predators may be on the rise. Rinse off, rub out or poison them before it becomes worse. 


Green thumbs down

to mold on the soil surface of houseplants. You're overwatering! Plants use less water when light is low. Any excess can fuel moss growth or root rot, so back off and let the soil dry down between waterings.

Originally published 12/13/03