Gardening: Stunning rex begonias thrive with proper care

Not all rex begonias tolerate heat well, and they tend to do best with bright indirect light when they are outdoors and away from direct Texas sun.

Not all rex begonias tolerate heat well, and they tend to do best with bright indirect light when they are outdoors and away from direct Texas sun.

Special at the Star-Telegram

Its name is the ‘Rex’ Begonia, and as far as I’m concerned it is the king of the plant kingdom when it comes to the stunning foliage. I have been fascinated by this plant since I was probably 8 or 9 years old.

It was difficult to find rex begonias back then. You’ve seen them in magazines and gardening references. They were offered in seed catalogs, but the seeds were like dust and it was apparently impossible to germinate them and become real plants.

It was a real joy to see this magnificent plant become one of America’s darlings – widely available online and commonly sold in nurseries and florists. It is as if the dreams of a young horticulturalist have come true.

What would you like to know …

Begonia rex-cultorum. The Missouri Botanic Garden says this name is applied to a group of cultivated begonias from the wild species Begonia rex somewhere along the line. The species is native to northeastern India, southern China, and Vietnam.

Hybridizers have gone crazy with this wonderful plant. You can Google it until your fingers are worn out. You will find hundreds / possibly thousands of cultivated varieties on the market.

The leaves of Rex Begonias display an endless array of jewel-like tones including silver, pink, purple, red, pink, and green, often streaked, swirled, and speckled. The size of the leaves varies from 3 or 4 inches to the size of a plate. They are borne in clumps or on extremely shortened stems.

When I first bought my 30 x 60 foot greenhouse, I filled half of it with small rex begonia grafts from an out-of-state specialist. I bought 300 varieties and planted them in 1 gallon pots. Most of them loved this greenhouse and I quickly had to repot them in 3 gallon containers.

By the end of the first summer some were fading from the Texas heat so my herd was thinning out. Eventually I went back to my favorite 30 or 40, and cultivated them for many years.

From these years of experience, I can tell you that not all rex begonias handle Texas as well. Some are easier than others. And I don’t think there is much reason to send you out looking for specific variety names. There are simply too many on the market and producers are turning to their own exclusive types.

In general terms, however, I have always found that most rex begonias work best with bright indirect light when they are outdoors – not direct Texas sun. I grow mine where I would grow ferns or hostas, except I keep them in pots so that I can take them to the greenhouse or home during the winter.

I choose a loose and very organic soil. I actually mix mine which is 50% sphagnum peat moss, 20% finely ground pine bark mulch, and 15% expanded shale and horticultural perlite. Because this mixture does not contain any nutrients, I use a dilute solution of a nitrogen-rich, complete and balanced, water-soluble plant fertilizer every time I water my plants.

Most begonias have showy flower clusters, but most rex begonias do not. For this reason, I keep the flower stems pinched from my plants so that all of their energy can be spent on producing more leaves. As the old leaves unravel, I pinch or cut them.

Rex Begonias prefer a soil mix that stays moist at all times – not wet, but certainly never dry to the point of wilting. They use a lot of moisture during the growing season.

If you grow rex ​​begonias indoors, place them on the brightest window sill available. Protect them from freezing weather and don’t let them touch very cold glass either. Rotate the plants every few days to keep them symmetrical. If you transfer them outdoors during the growing season, do so with caution. Do not suddenly expose them to bright light. It could burn their tender leaves.

If you are interested in propagating begonias rex, the easiest way is to cut the leaves. Use a very sharp knife or a single-edged razor blade to remove a healthy leaf of normal size. Cut off its petiole (“stalk” of the leaf) so that it is only 1/2 inch long. I use sharp snips to cut the leaf around its edges so that it is about half of its size originally.

Fill each pot with a mixture of equal amounts of sphagnum peat moss and perlite and soak it well. Use a pencil to create the insertion holes, one hole per sheet. Stick the leaf in the potting soil so that the base of the blade is barely covered with soil. Firm the soil around the base of the cutting. Add one or two more leaves if you wish, then water the potting soil abundantly.

Place the pot in a bright location, out of direct sunlight. Cover it with dry cleaning plastic to trap moisture around the leaves as they form roots. When they offer slight resistance when you pull gently, it’s time to put them in 4 inch pots. New plants will develop from the base of each cutting.

Of course, you can grow your rex from seed as well, but take Neil, 14, many years ago: you don’t want to go. The seeds are too small and the work is too tedious. Moreover, they do not “come true” from seeds. Leaf cuttings are much easier.

You can hear Neil Sperry on KLIF 570 AM on Saturday afternoons from 1:00 p.m. to 3:00 p.m. and on WBAP 820 AM on Sunday mornings from 8:00 a.m. to 10:00 a.m. Join him at and follow him on Facebook.

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Terri S. Tomasini