Grow 495: Orange tree, male, female, tree, poinsettia

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Pinching is proper when you want bushier plants 



I was given an orange tree three years ago. It is very healthy. I water and fertilize it regularly. It is now four feet tall, one limb straight up and down. How do I get the tree to bush out so it looks like a real tree? When will fruit appear?


Dear D.Z.,

A general pruning rule applies -- to promote branching, prune during active growth. After growth begins in spring, pinch the new branches -- clip off the tips. Pay special attention to the tallest and widest limbs. Keeping those pinched yields the best return in breaks -- new branches lower on the plant. Citrus trees don't break readily, so you may have to pinch several times this year, and still not see significant results until spring 2004.

Fruit follows flower. Citrus may bloom at two to six years old, but only if they have both adequate energy and the correct environmental cues.

To plants, light is energy. Citrus need full sun, even in winter. Is the light in your window equal in strength and duration to a winter outdoors in Florida or Arizona? During winter here, only a spot under grow lights or in a conservatory can measure up -- if grow lights are on for 12-18 hours every day and if supplemental lights come on in the greenhouse on overcast days.

So your tree may have enough light to produce leaves, but not flowers.

As for environmental cues, grow the tree a bit drier and cooler in winter, to increase the chance of bloom the following spring and summer. I wrote in this column on December 29, 2001 about the general care of citrus, including their need for a dry, chilly season to stimulate fuller bloom during the next warm, moist period. On winter nights, temperature in a professional orangery drops into the low 50's. By day, it climbs only to the high 60's.



You wrote about male and female shrubs. Are there male and female trees, too?


Dear J.V.,

Yes, indeed. Some species that have pollen-producing flowers on one individual and seed- or fruit-forming flowers on another are ginkgo, Kentucky coffeetree, the maple called box elder, mulberry, persimmon, poplar, staghorn sumac, tree of heaven, white ash and green ash. (Despite its similar common name, mountain ash is not related to the white and green ash. Every mountain ash can produce fruit.)

This knowledge can be used to advantage if you plan ahead and purchase male varieties to avoid the smell of ginkgo fruit, escape cleaning up rock-hard pods under Kentucky coffeetree or seeds from ash and box elder, or to know that your poplar won't produce snowy, blowing seed.

On the other hand, you'll need a male of the species within pollinating range of a female if you want to draw birds with mulberry fruit, provide nutritious box elder seeds to birds and small mammals, enjoy the sight of red "horns" on a sumac or munch a homegrown persimmon. Other things to know are that only male varieties of ash are susceptible to ugly, stunting ash flower gall disease, male tree of heaven flowers are malodorous, and memory-enhancing herbal preparations comes from female ginkgo trees, from the fruit.


Short reports

If your homegrown poinsettia seems pale and thin..

... compared to those you see in stores, it's not a problem but a reflection of how professional techniques differ from ours at home.

In the greenhouse, a poinsettia's growth is governed not only by light and water but by growth-regulating chemicals -- synthetic versions of plant hormones applied to promote denser branching, shorter, thicker stems and more concentrated leaf color. You probably can't provide as much light or control its duration like a professional can, so your plant has less energy and wouldn't respond properly to the growth regulators even if you could obtain them.

Be happy with the poinsettia you nurtured all year -- it's adapted to your growing conditions, so it will remain a steady presence. A new, greenhouse-raised plant will shine for the holidays but will eventually have to reconfigure itself to the lower light and drier air in your home. If you keep this year's acquisition as a houseplant, expect it to stretch out, lighten up and drop some lower and interior leaves. 


Green thumbs up

to stepping outside on Christmas. Fill the bird feeders, admire your evergreen collection, and take snippets of fragrant pine, fir, arborvitae, lavender, sage or thyme indoors to refresh your holiday decorations.


Green thumbs down

to the new age use of de-icing salt. Used to be we spread a bit to start breaking up ice, then shoveled. Lately it's being used sans shoveling, in quantities as if for traction. No wonder more plants are burning!

Originally published 12/21/02



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