Rex Begonia Page
Now, I’m not sure how Mabel Corwin feels about the moniker “Rex Queen” but she surely is that after all the fabulous rex hybrids she has created. When you talk about rex begonias, Mabel’s name has to come up in the conversation. Having said all that, I want to tell you that Mabel is more than just a rex grower and hybridizer, she is a fabulous grower of all types of begonias. If you have ever visited Mabel’s greenhouse and shadehouse you will know, without a doubt, there isn’t a single type of begonia that she doesn’t grow and doesn’t grow to perfection. Of course her collection of rexes is very impressive but she has collections of everything and they’re all impressive.
Mabel has been growing begonias for more years than I’ve been alive which is to say she’s been growing for a long time; and no, I can’t quote that actual year she started growing but I think only Rudy Z. has been in the Society longer. In all her years of growing she has undoubtedly learned a few tricks but I have a suspicion that she has always grown great begonias. Mabel is always willing to share her growing tips with anyone who asks. She has the most charming manner in that she always can lure the listener into whatever tale she is spinning about begonias. I remember one memorable day when she told the story about how she sat and watched bumble bees pollinating her B. pearcei and then noting which plant they had just come from so she could write down the cross. That’s how tuberous begonia, B. ’Bumble Bee’ got its name.
has held numerous offices in ABS, besides all her good plant work, and
she must have done a great job because everyone still loves her. She’s
also been active in the Round Robins so that she could share her
with others. Mabel, along with her husband Ralph, might well have
the aims and purposes of ABS because they just seem to follow those
naturally. They are always the gracious hosts to anyone who has stopped
in to visit.
Like several older members of ABS Mabel is always saying, how she can’t do this anymore and she can’t do that, but I haven’t noticed yet that she’s really stopped anything or is slowing down. She still helps out whenever she can and even supplied some fabulous plants for a display at last year’s Convention.
Rexes are considered the gems of all the begonias but if Mabel were a begonia they’d only be semi-precious.
Mabel Corwin’s secrets: how she grows her fabulous rexes
Today I grow all types, from B. vitifolia that grows through the top of a 10-foot-high lathhouse to tiny-leaved ones growing in bowls. People often ask me which is my favorite. That is a little like asking me which of my children I love the most. However, I do have a special fondness for rexes. The brilliant colors and interesting textures always attract attention.
Rexes require more humidity than other begonias. I think that is the main reason many growers find them difficult. Lack of humidity causes the leaf edges to become crisp and dry and the plant simply does not flourish as it should. I have about 300 rexes growing in my shadehouse. This is the way I handle the problem: I place all of the rexes on low benches. The ground is covered with a thick layer of gravel. During warm weather I water the gravel. As the water evaporates it cools the air and adds humidity. Most people grove on a smaller scale. Humidity can be added by placing pots on trays of wet gravel. Grouping plants together and placing a pan of water nearby also works. Indoors a humidifier vvould be helpful. Rexes also can be grown in terrariums if there is no other way to provide the necessary humidity. The right amount of light is important to bring out beautiful colors. They should not have any direct sunlight. One of my reasons for growing on low benches is that the light is less intense. It seems to be just right for rexes. I never grow rexes in hanging baskets. The light is too bright and the air too dry. They are sometimes grown under thebenchzs in the greenhouse. This works well if good air circulation can be maintained. Usually we are told the grow rexes warm. I grow mine in the coolest part of the slladehouse.
During the winter our low temperatures are often around 40 degrees F. We usually have a few nights that are colder. Most of the plants have no leaves, or few leaves—they simply rest during the cold weather when the nights are long. In February new growth starts and during the spring months the growth is very fast. While the plants are resting I check each one carefully. I usually pinch off the tip of the rhizome or cut it back to the edge of the pot if it has grown over the edge. This forces new growth along the rhizome and makes a full compact plant. If it has an upright rhizome I cut it back part way. If the plant has been growing in the same pot for a year I usually pot up into the next size pot. Usually the plant needs to be set slightly lower and sometimes centered in the pot if it is growing off in one direction. I do this potting in March and April, when they are growing fast, and I start to fertilize.
Rexes respond to a regular feeding program during the spring and summer months. I start with an all-purpose formula such as 14-14-14 or 20-20-20, then alternate with 15-30-15 or something similar. I taper off the feeding in late summer when growth slows down. In recent years mildew on rexes has become a real problem. Prevention is very important. Good air circulation is absolutely necessary. Some of us have found Funginex to be a good preventive spray. Once you have mildew on a plant it takes constant vigilance to keep in under control. It can spread very quickly when conditions are right. Some varieties are much hardier than others. Usually those with soft, hairy leaves are a bit touchy. Spiral-leaved varieties may be difficult. However, many new hybrids are being introduced that are easier to grow.
When I make a cross I always make sure that one parent is a strong grower. This usually results in a strong plant that is easy to grow. If you have adverse conditions, or are a novice you should start with varieties that are easy to grow, such as B. ‘Helen Teupel’, B. ‘Merry Christmas’, or B. ‘Vista’. There are a few varieties that I always keep in the greenhouse. One is B. ‘Purple Petticoats’ that has won many prizes for me. I have tried it out in the shadehouse, but after a month or so it sulks and lets me know it is unhappy. Others that need greenhouse conditions are B. ‘Glory of St. Albans’, B. ‘Helen Lewis’, and B. ‘American Beauty’.
Mabel Corwin was an excellent grower and hybridizer of rex begonias. She was THE expert in their culture. The two articles above appeared in The Begonian, the official magazine of The American Begonia Society. Mabel has been sorely missed
More pictures of Rex Begonias