The fancy leaf begonia known as the REX likes warm, humid conditions in filtered sunlight.
Lovers of the Rex begonias consider them the most, brilliant and majestic of all foliage plants, earning the fitting title “King of the Begonias.”
The conditions under which the Rex is found growing in its native climate are indicative of the requirements the plant needs when growing in the greenhouse, sunroom, enclosed porch or indoors.
The Rex Discovery
The first Rex begonia was found in Assam, India, in 1858, where they grow to perfection in a tropical region of dense forest. Heat and heavy rains made the air foggy with moisture – perfect for these humidity-loving plants.
These facts tell us that in our homes they must be kept moist, in a fibrous rich soil, fast draining. They grow best in diffused indirect light in a window garden.
They thrive under indoor fluorescent plant grow lights with perhaps slightly less light than African violets require.
Grown From Rhizomes
Rex begonias grow from a fleshy root-like tuber called a “rhizome.”
This rhizome usually lies on the ground, and masses of small fibrous roots grow from it.
Some varieties are upright growers where the rhizome grows into a vertical position, making a plant reach maybe two to three feet tall.
The commonly-grown varieties of Rex, however, seldom become more than 18″ inches tall.
Showy Fancy Leaf Begonia Foliage and Yes – Flowers
The leaf stems are long, erect, very fleshy and hairy. The foliage colors and variations are in countless different combinations.
Although Rex begonias are known for this colorful “plumage,” they also produce flowers.
Sometimes the flowers are unshowy and borne beneath the foliage. Other varieties produce flowers above the leaves that are very attractive, and occasionally fragrant.
As an example, the old-time variety call ‘Curly Fireflush’ has dark green leaves, edged in black, with the entire leaf covered in red hairs.
Its new leaves resemble red velvet, and the beautiful white flowers are very fragrant.
Rex Loves A Humusy Soil
Rexes should have a soil mixture firm enough to hold large plants, yet porous enough for proper drainage.
A medium of peat moss and one-third perlite with a few wood ashes and crushed charcoal makes a suitable mixture. Generally, a soil that grows quality African violets should be satisfactory for Rex begonias.
Drainage Important and Feeding Too
Good drainage is important. Place at least one inch of broken crockery in the bottom of the pot before filling the container with the soil mixture. Keep moist but not drippy wet.
Use a well-balanced fertilizer like Miracle-Gro plant food every two weeks, and be sure to follow the instructions given for house plants.
Feeding frequently but lightly is much better than an overdose.
PRO TIP: I have found that 1/4 teaspoon of nitrate of potash to a six-inch pot will produce strong leaves and beautiful blossoms.
The Begonia Rex and Winters
Few Rexes go dormant in the winter, but if one should drop its leaves, do not throw the plant away.
Set the plant aside and water just enough to keep the stem firm – once a week or every ten days.
When new growth starts, prune, keep the soil moist, and feed every two weeks with a liquid feed.
Most Rex varieties bloom in the fall or early winter. The use of nitrate of potash through the winter will keep the leaves firm and prevent dropping.
Rex Pest and Disease
Rexes are relatively free of disease, and few pests attack them. The reason is that “bugs” do not like the high humidity and daily spraying the rexes require.
Should mealybugs, red spider, thrip or aphids attack plants, deal with by spraying Neem or Malathion.
If plants are put outdoors in the summer, they must be in a very protected location that is cool and damp.
Such a place will harbor leaf-eating, slimy slugs. Poisons made specifically for these pests can be used to control them.
We recommend garden safe diatomaceous earth for slug control.
Some try scattering cabbage or lettuce leaves about in the evening to help. The slugs gather on the leaves, gathered in the morning and destroyed.
Rex Begonias are truly showy fancy foliage plants worth the effort to grow.
The Tiny Begonia Seeds
Rex begonias grow easily from seeds.
A small clear plastic seed tray with good drainage and damp screened sphagnum moss pressed down firmly is ideal for seed sowing.
Rex seeds are so tiny they appear to be rust colored dust. It is a miracle when they sprout so readily in about ten days.
Sprinkle the seeds thinly over the damp moss and do not cover them. Place the top on the tray and set in a warm, dark place to germinate.
Bottom heat will speed germination.
After the little specks of green begin to appear, gradually remove the top of the seed tray and bring the plants into more light.
When the seedlings have four to six leaves, transplant to a flat of peat moss and sand.
Transplant the seedlings two inches apart, being careful not to damage the small roots when separating them.
They may be left in the flat and fed every two weeks with liquid food until they are three or four inches high and ready for three-inch pots.
This will take three to four months.
New varieties and different leaf patterns result when two different rex begonias are crossed.
After you become a proficient grower of rex begonias, you will want to try your hand at cross-pollinating.
This is easily done on a bright, sunny morning when the pollen is ripe, and when the yellow, twisted pistil becomes slightly moist with a sticky substance and is ready to receive the pollen.
When the seed pod begins to turn brown, it is ripe and ready to be picked.
Put it in an open envelope or dish until it dries completely and the seeds are ready to be tapped out of the papery seed pod.
Growing Rex From Leaves
The leaves of rex begonias will root and produce more plants exactly like the one from which the leaf has been taken.
Use mature, vigorous Rex leaves from a healthy plant, leaving the leaf’s stem intact.
On the underside of the leaf, at the junction of the veins, cut through the veins just below the lateral (V-shape) but do not cut clear through the leaf as this will cause it to rot.
Be sure to use a sharp knife that will not bruise the leaf.
Place this leaf in a jar, propagating case or plastic box filled with two inches of damp peat moss and sand or vermiculite, with the back of the leaf down.
Pin the leaf down using toothpicks, or hold in place with pebbles.
Do not cover the leaf with the rooting medium, but cover the stem a quarter of an inch. Keep moist, not wet, and place in a warm, shaded place.
It will take from two to three months for roots and subsequently new plants to form.
They are then divided and treated like young seedlings.
Propagation is possible from leaf wedge cuttings. Trim mature leaves to three inches and cut between the large veins. Be careful to include a small portion of the main stem with each wedge.
Dip the wedge in a rooting hormone, and set 1/4-inch deep at an angle in the rooting medium. Small plants grow from the bottom of the wedge.
Three to five wedges may be made from one large leaf.
Begonia Culture of Rex
Culture of rex begonias differs slightly from that of more commonly grown begonias.
- Rexes will not tolerate wind or hot sun
- They do not like wet feet.
- Rexes must have free air circulation.
- The Rex are heavy feeders
- They can be grown outdoors in the summer in the shade if sprayed twice a day.
- They will grow indoors the year round, or in your living room – if enough humidity can be made available.
A glass or plastic case is a great aid in growing rex begonias in the house.
They may be set on a tray of moist sand or gravel.
If you have a table in a dark corner that could have a fluorescent light unit placed over it, is an ideal place should for your rex begonias.
Rexes can also be grown in pots using the double pot method.
Line the large pot with damp sphagnum moss and set the small pot with your Rex inside.
Keep the moss damp and the roots of your plant will not dry out.
Rexes that grow upright may be grown like an ordinary cane or angel wing begonias.
However, they require the same warm, humid conditions regular rexes must have.
Use bamboo cane stakes to keep the uprights in presentable condition.
Tie the branches loosely to the stakes with soft yarn, or use soft twistem wire for tying.
Place the stakes and ties so they will not show from the outside, thus giving the plant a graceful, natural appearance.
Prune the plants in spring before new growth starts, leaving two nodes or leaves on each branch. This gives a compact plant with fresh, new growth.
Hundreds of different named variety Rex begonias like ‘escargot begonia’ are available from commercial growers with many leaf different and exciting colorations.
It is wise to start with less expensive varieties. They are usually the easiest to grow, and when you become a successful grower, you can try those plants that are more rare and difficult.