Nearly all types of begonias can be started from tip cuttings, even rhizomatous. A tip cutting is basically the end portion of a stem. It is removed from the plant, rooted, then planted and grown into an exact copy of the original plant.
A tip cutting has to have certain elements in order to grow a good plant from it. As a general rule, begonias won’t send out new growth from a node where they have previously had a bloom. Nearly all begonias that won’t grow from leaves also won’t send out growth from a node they bloomed at. This element doesn’t apply to tuberous, rhizomatous and rexes, they will send out new growth from any rooted part of the plant.
The illustration at the left shows a typical begonia stem and it’s various possible components. On a begonia stem, there is a node above each leaf. This node can have a bud that will grow into a new stem someday, it can have a flower cluster grow from it, or it can be dormant and not showing a bud. Any node that doesn’t have flowers or the scar left after the flowers have fallen off, has a bud in that node whether it shows or is completely dormant and not showing.
A good cutting needs to have a node with a bud on it for it to grow into a proper plant after it’s rooted and planted. The bud is where all future basal growth will come from as the cutting grows. Using cuttings where the nodes have had blooms will result in plants that can never send up new basal growth. The illustration shows how to determine what nodes you have. If you look at a node and there is a leaf or the scar left after a leaf has fallen off, and there is no scar left from a flower, then there is a growth bud there whether you can see it or not. When leaves and flowers fall off they both leave round scars on the stem where they were. So, a bare node that has two scars is a node that previously had a leaf and a flower cluster. If this explanation isn’t clear, the illustration on this and the next page should make it clearer for you.
The best cuttings are ones that have never bloomed since they have buds in all their nodes that will eventually grow into new stems and new side growth. Any stem cutting though, that has at least one good bud in the lowest node will be a good cutting.
In the illustration (above) you can see that the lowest node pictured has a scar from where the leaf was attached. It also has a bud. That is the main requirement of a good cutting, no matter what the rest of the nodes on the cutting are.
A tip cutting should also have at least a couple leaves. One without leaves may root but not as easily or as quickly. You can also make a regular stem cutting from parts of a stem that don’t have the tip. For those types of cuttings, since they don’t have the tip, need to have at least two nodes with buds. One at the base of the cutting that will be buried in the potting mix and one to grow into top growth. It should also have a leaf if possible. Woody hardened stems will root without leaves however. They do take longer though.
This illustration (to the left) shows a good tip cutting. It has buds in the leaf nodes for future stem growth as described previously.
When taking a tip or stem cutting cut the stem about half an inch below the selected node.
It’s possible that if you have any stem rot while rooting the cutting, if you have cut closer than half an inch below, you could lose that lower node. Half an inch gives you some margin.
Cutting further than half an inch below leaves too much unnecessary stem below the lowest bud.
When you get ready to pot up the cutting after it roots, it will be hard to get that lowest bud buried in the potting mix if too much extra stem is left below it.
When rooting the cutting, you should remove any leaves from the lower nodes first, since those parts will be buried eventually anyway can could rot.
In the illustration below right you can see how to pot up the newly rooted cutting.
Put the cutting as low in the pot as possible covering at least one good bud. In the illustration, you can see the importance for doing this. The buried buds will eventually grow into new shoots and all the future basal growth.
Without a buried bud, the cutting will of course still root and grow. It won’t be able to send up new basal growth however. It will only be able to branch somewhere above the pot.
The only time you should use cuttings without buds to bury is if you’re going to grow a begonia as a standard. Since a standard should be just one main stem, ordinarily bad cuttings are perfect for that purpose.
For begonias that are everblooming and hard to get good cuttings from, one tip is to first prune the plant. Then take cuttings from the new growth that comes up.
Credits / references:
Brad Thompson | Brad’s Begonia World