By Brad Thompson
As a grower with limited growing space, I’m always looking for novel ways to grow begonias. I try to use my space effectively for maximum show and squeeze in as many varieties as possible. Over the last few years I’ve grown begonias on moss covered boards, on trellises, in wall pocket type bags as ways to use space. Lately I’ve been working on growing begonias as standards. In case you don’t know what I mean by a standard, this is a method of growing a plant into a treelike form with one central stem and full at the top. This article is to share some of the methods and which varieties are likely to make the best standards.
The hardest part of making a standard is figuring out what Begonia to use. Here are qualities to look for when choosing the plant. You need to pick varieties that are balanced between easy blooming and good branching. If you choose one that blooms too heavily and rarely branches, you’ll have great difficulty in getting it to conform to a standard. On the other hand if you choose one that branches really well but rarely blooms you’ll end up with a standard that never blooms. No sense in putting in all that work on a plant that doesn’t perform.
Another important trait is a plant that will grow one sturdy straight stem, but that will also put out manageable side shoots when pinched out. Some begonias such as B. ‘Sophie Cecile’ would put up a nice sturdy main shoot, but you might have trouble keeping it in check since it’s such a strong grower. Also, the amount of pinching required to make it conform would almost guarantee that you’d never get any blooms since it’s a shy bloomer to begin with. At the opposite, a plant such as B. ‘Tom Ment’ would make a lovely standard if only you could get a stem to grow two or three feet tall that would be sturdy enough to support all future growth on the plant.
There are many choices; in this article I’m trying to refer to begonias that nearly everyone is familiar with. A cane that would be nearly perfect in traits to grow as standard would be B. albo picta. It can send up nice sturdy shoots, sends out nice side growth when pinched, and still blooms well. An example of a shrub that has nearly perfect traits is B. echinosepala. There are many, but I’m listing these two as examples to follow when choosing. Begonias that probably wouldn’t make good standards are Semperflorens or Semperflorens hybrids such as B. ‘Christmas Candy’. They bloom well, but are nearly impossible to branch once they start blooming.
Creating a standard is a fairly simple process, but you must be prepared to spend a year or two growing one to full glory. The first year will be spent mostly getting it to the height you want and the second year will be spent pinching it to make it fill in.
I try to start cuttings specifically to make standards with. For this purpose, I try to find those bad cuttings that we normally throw away, those that have bloomed up the stem. For normal purposes these cuttings are not good because any plant you create from them will have no basal growth when planted. For making standards, a cutting that won’t make basal growth is perfect.
Once the cutting is rooted, pot it up as you normally would. It helps to put in a tall stake right from the beginning so you can keep the plant tied up straight as it grows. It will also help you remember that you’re making a standard.
I can’t tell you how many times I’ve forgotten and pinched the tip. Continue to tie the plant to the stake as it grows and remove any side growth that might try to pop out. One important note, make sure you don’t tie the stem too tightly. This main stem will grow larger with time and the tie can cut right through it. The flexible stretchy plastic ties like you would use on tomatoes work best to avoid this problem. Later when the plant is mature you can switch to the wire plastic ties. It’s best to keep the standard staked it’s entire life whether the main stem seems really sturdy or not.
You can grow the standard to whatever height you choose, two to three feet is usually a good height, but you can make it taller if you like. Take into account that it will end up taller after you pinch it out. I encountered a problem I hadn’t considered when I made them, that they were too tall to fit in my covered pickup when I wanted to take one to a show . When the stem is as tall as you would like, pinch out the main growing tip. Make sure there are side buds where you pinch out though. If it’s blooming heavily and you pinch it, it will branch out down lower wherever there are side growth nodes. You can try growing it in less than the best light during this process to keep it from coming into bloom.
As the side shoots come out, let them come out a few nodes and then pinch them again. The first year you should keep up this pinching every few nodes until you have a shapely plant and not worry about blooms. Any new basal growth that comes up should be cut completely out at or below the soil line.
For potting, at first it should be kept a little under-potted to avoid overwatering. If you find it hard to keep upright, either use a clay pot or set the plastic pot inside a clay pot for stability. As it matures the standard should be treated like you would any Begonia with regular fertilizer and so forth. Determine future pot sizes by how much growth is at the top, not by how tall the stem is. The pot should be about one third the size of the top growth at its most mature. You can also determine that it needs a bigger pot if it starts drying out faster than other plants around it.
Pinching will be a yearly requirement to keep the standard in shape. In the spring you may also need to do some pruning to keep it in line. Make sure not to prune back so hard that you remove most of the good nodes. If you prune really hard you may undo part of the previous year’s work.
Standards make really spectacular additions to your gardens and collections. If you’re trying it for the first time, since it is a long process, do lots of different varieties at one time so you won’t be as disappointed with failures. It will take some experimenting to find good canes and shrubs to use. Some might seem like good choices, but their branches aren’t strong enough to support themselves in the tree form. Others might seem fine at first, but turn out to be varieties that are prone to die back. Remember, the plant has to live it’s entire life off one stem so it has to last long time. I made a wonderful standard of B. ‘Laura Engelbert’ one year, but it was only great for one year. It died back all the way to the main stem over that next winter so although it was beautiful, it wasn’t long lasting and not worth doing again. Hope you give standards a try, they are fun and rewarding, even if they do take a little work.