Rex Begonias As House Plants

Rex Begonias aka the painted-leaf begonia grows on window sills, on plant stands, tables, and even a breezeway. At one time, the Rex begonia was thought to be strictly for the greenhouse hobbyist. Such is not the case anymore!

Are Rex Begonia Houseplants? 

Today anyone can have the necessary cultural know-how to grow these most luxuriant and beautiful of house plants. Rex begonias can be grown practically anywhere in the house where there is good light and some sun.

The beautiful leaves of the Rex Begonia

Rex Begonia Needs No Extra Special Treatment

Surprisingly enough, most rexes do not need extra-special catering to, as is believed by many people. By nature, these plants want and demand:

  • Humidity
  • Constant moisture 
  • Rich soil

Here are the basics for a good Rex Begonia potting medium. 

  • Two parts peat moss
  • Two parts garden loam
  • One part finely sifted cow manure
  • One part sand (not sea sand!) 
  • One handful of charcoal
  • One handful of bone meal is beneficial

Mix all these ingredients thoroughly. The hand-over-hand method proves the best and safest, as the hands will detect any coarse materials that might have escaped the sifting. 

Get the “feel” that the mixture is uniform. After mixing these ingredients, moisten thoroughly so that all of the medium is damp, but not wet. 

Now the potting process is ready to begin.

Never Allow Rexes To Dry Out

At no time should a rex begonia be allowed to become dry. These begonias demand moisture from the soil – top to bottom of the pot. At no time should the mixture be drippy wet. 

Do not allow the pots to sit in water for any length of time, as this can cause root rot. Water thoroughly each time (never just the top soil). 

Water again when the soil at the top is slightly crumbly to the touch. 

The water used should be somewhat tepid so that the tender root system does not become shocked and chilled by cold temperatures such as would come from the ordinary faucet, especially in winter.

The one thing many learn when they start with rexes is that they resent cold, wet feet. They soon learn that Rexes need to be watered in the daytime rather than at night, especially during the colder months. 

Daytime temperatures usually dry off excess moisture and warm up the soil, thus creating a warm evaporation of moisture up around the leaves. 

Yet, if a rex is dry, it should be watered regardless of the time of the day. 

Plants watered at night are more susceptible to Botrytis blight. If the weather is cool, be sure the plant is well-drained and not left standing in water overnight.

Watering from the top causes no injury, and it is quicker than placing the pots in water to soak up the moisture. 

If a plant is not receiving thorough saturation of the soil, it may show signs of dryness by a lack of growth and eventual drooping and dropping of the leaves.

Humidity Required

Rexes require humidity at all times. All begonias need it. It’s easy to provide the humidity necessary for house plants. 

During the summertime, with windows open, and moisture in the air is provided naturally. 

Even with air conditioning, during the day when there is hot, drying air stirring, humidity can be given by spraying with a fine mist of water or setting the pots on moist pebbles, sand, or vermiculite. 

If you spray the leaves, care should be taken to keep the plants out of direct sunlight until the moisture has dried. 

In the winter, supply the humidity by having a bubbling teakettle on the stove during the day.

Rexes Like Fresh Air Too

Rexes require fresh air as much as people. If they are on the window sill, it is best not to have the winds and hot air of summer will take moisture out of the leaves and cause browning. 

In the winter, the air is too chill. Open a window and allow fresh air to come from another window to the plants indirectly.

Bright light and some sun are needed by all rexes at all times to help keep the leaf colors bright. The sun (and fresh air) helps to prevent fungus problems.

Details on the growing the Houseplant Rex Begonia under fluorescent lights.

Many varieties can gracefully accept the early to the mid-morning sun, and late afternoon sun in summer. I find many varieties will take, and be most happy, in full winter sun, especially the darker-toned ones.

Some of the silvery-toned ones are likely to burn, but if given the mid-morning sun, they will respond with a lustrous sheen. The sun does much in the deepening of the color tones in rex leaves.

Rex Propagation

Rexes are propagated by various methods. 

The leaves may be rooted in water or a mixture of peat moss and sand. The rooting medium must be moist, and the leaves must have a high percentage of humidity while they are first rooting. 

The plantlets come up in much the same way as do African violets. 

For the first potting, use pure peat moss and 2 1/2″-inch pots. I prefer clay pots, though other growers praise plastic containers. 

After potting, the young plants are watered thoroughly, allowed to drain well, and then set back into shady quarters for a few days so that they will have a chance to start new growth. 

Young plants will thrive if the small pots are grouped together and snuggled into moist peat moss.

Propagating From Wedges

Experienced rex begonia growers often propagate from wedges of the leaves. You’ll need a sharp knife and a pair of sharp-edged shears. 

wedge propagation of a begonia leaf

The knife is for cutting the leaves from the plant, and cutting away the leaf stem about one-fourth to one-half inch from the sinus, for it is from the sinus that the rootlets of the new plants grow. 

NOTE: The “sinus” is that portion of the leaf where the leaf stem joins the leaf itself.

With the shears, the wedges are shaped – meaning to cut away the excess leaf.

The wedges need to be three inches high at the most. Some people make them triangular, some apple-shaped, but the shape of the wedge has no bearing on the fruitfulness of it.

When the wedges are shaped, usually the cut stem and sinus is dipped into a hormone powder, then carefully inserted into the rooting medium to just above the sinus, sprayed in gently but thoroughly with tepid water to settle the medium. 

At no time should the medium become dry. Put the tray of wedges where it will receive uniform warmth, night and day, but no direct sun. 

The rooting process is usually quicker if they are kept uncovered, especially in the summer, when there are usually spells of very humid weather. 

Wedges left uncovered are much less likely to rot before roots have a chance to form.

Leaves used for propagation, and especially for wedges, must be strong and healthy.

If one wishes to lay a rex leaf on any rooting medium, best results are obtained by thoroughly moistening the medium first, and draining off any excess moisture. 

Begonia leaf propagation showing where to cut the veins

Fine cuts may be made in the large veins on the back of a rex leaf, the cuts treated with hormone powder and the leaf laid carefully and smoothly on the rooting medium. 

It is then pinned down carefully (I use hairpins) so as not to penetrate the cut veins.

Leaves rooted in water should be potted as soon as the roots are an inch long.

rooting begonia leaves in water

I’m afraid I like ALL rex begonias, but my favorites are the colorful ones that have personality plus. Many, in my opinion, will grow anywhere, anytime, under any and all conditions. 

Their handsome, satiny, dark leaves spotted red and purple. 

Yes, I am a fancy leaved rex begonia hobbyist, an addict could be the word, but I enjoy them to the utmost. The more I have, the more I want, and so it will be with you!

By: Lena Jacobs