By Brad Thompson
The following are the ins and outs of pinching.
1. What is pinching:
Pinching is the removal of the plant’s growing tips to force it to put out side shoots and branches. It involves removing the very tip of each stem (pinching it off).
2. Who to pinch:
While you can pinch any begonia to promote branching there are some types that you probably shouldn’t and some that don’t require it. As a general rule large upright canes, larger flowered tuberous, and thick stemmed begonias shouldn’t be pinched. The large canes and the thick stemmed varieties don’t usually branch well even if pinched, and pinching those will leave a stair stepping type scar/stump where you pinched which will make the plant not look as nice. These also have larger leaves and forcing them to branch too much may over crowd the plant. The large flowered tuberous are not supposed to be branched because it will cause the flowers to be smaller which will ruin the plant for any shows. ( you can pinch out the flower buds on young tuberous plants to give them more energy and larger flowers later though). The type of begonia that responds the best to pinching are small to medium leaved canes and shrubs, especially if you are growing them in a basket. Pinching will make your baskets full and help keep them growing symetrical. You can also pinch the tips on your rhizomatous (after they have bloomed) to make them fill the inside of the pot instead of crawling over the edges. Some types that branch well on their own may not need any pinching, but you’ll just have to watch and learn which of your begonias fit that catagory.
3. Why to pinch:
Let me give you an example. Say you have a plant in a basket with three nice stems and you don’t pinch. This is a variety that doesn’t branch well on its own. These three branches keep growing out and then bloom, maybe during the growing season a couple more stems come up from the base, but basically all you’re getting for a seasons growth is three blooming stems. Ok, let’s say that instead you had pinched this plant, each stem put out two side shoots for each stem you pinched out making six stems. A few weeks later you pinched out the tips on those six stems and each of those pinches resulted in two more new side shoots. Even if you stopped right there you now have twelve blooming stems with just pinching two times. Of course you can usually pinch more times than that before you have to let them go and bloom but I hope this example illustrates what a difference just a little pinching can do. Also you can get more than just two side shoots from each pinching and usually you do. Pinching your plants can also transform a plant that normally likes to grow tall, leggy and open into a full, bushy compact plant. An example is B. albo picta. I have seen that plant be five foot tall, beautiful but very open and not lush looking. I started pinching mine and transformed it into a lush, very full plant that was only about a foot tall that won numerous trophies and cultural awards so I know the dramatic effect that pinching can produce.
4. How to pinch:
To pinch your plants you need to follow what I already stated earlier. You remove the growing tip of each branch. The growing tip is that unopened bud at the very tip of each stem where the next leaf will come out. Usually you remove it by pinching it off with your fingernail (yes thats why its called pinching, and no I don’t know who thought of calling it that). Make sure to remove it completely to the base of the bud or the plant may continue to grow from there. You can also remove the bud and the new baby leaf below it to make sure you got it pinched off.
5. When to pinch:
On plants that you’re going to pinch, start pinching after pruning (or right away on plants that you don’t prune at all) as soon as the new shoots have grown out three nodes ( a node is the joint in the stem where the leaf is connected). The reason for this is that if you don’t wait till you get out three nodes then you won’t gain anything because after pinching out one bud where would it branch from? With three nodes, after removing the one node (the growing tip is a node too) then you are left with two nodes that will send out side shoots. These you let grow out three nodes and then pinch again. Usually a plant that is actively growing can grow out three nodes in three or four weeks. You continue pinching until about 6 weeks before a show to make sure the plant has time to grow out and bloom well in time for the show. Pinching will delay blooming but you will be rewarded with so many more stems that have blooms that it is well worth the extra wait besides the fact of how nice and full your plant will be.
I was amazed at the difference pinching made especially on plants that had a tendency to grow leggy or sparse. If you plan on entering shows and would like to win something for your efforts then you really do need to learn to pinch to have quality show plants but even if you’re just growing them for yourself you should still pinch for beautiful, full plants.
Credits / references:
Brad Thompson | Brad’s Begonia World