The Art of Proper Cuttings by Brad Thompson
This article will describe the different types of cuttings you can take for specific types of begonias and also the different rooting methods for each.
1. Canes and Shrubs:
Canes and shrubs are usually started using stem cuttings (a tip cutting is a stem cutting also). Any part of the stem that has growth buds will make a good cutting but the easiest part to use is the tip cutting with a couple of leaves. These can be rooted the easiest in plain water in small jars.
My theory on using the smaller jars, and the reason they seem to work better is that the cuttings produce a hormone into the water to cause roots to form and a larger jar dilutes too much because of the larger ammount of water. If you root in water, pot up the cuttings when the roots are about a half inch long.
Tip cuttings can also be rooted directly into regular mix or a peat/perlite mix with relatively good success. Bury at least one good growth node under the mix and water as you would a growing plant but don’t allow to dry completely out (don’t go overboard the other way either and keep soggy wet all the time).
Enclosing in a container under lights with warmth will cause them to root faster but make sure to use a sterilized mix to avoid fungal diseases. You can also root in plain moist perlite in a covered container.
If the weather is warm the cuttings should be rooted in 3 weeks to a month. Old canes or stems that you would ordinarily throw away because they are woody and don’t have any leaves can also be rooted but take a lot longer to root and produce plants. Cut the stems so that each has two or three good growth buds and stick them into mix burying one node.
I use a flat and stick them in rows. Some will not make it but since you would have thrown them away anyway you don’t have anything to lose and the flat can be stuck under a bench to root. Most canes and shrubs as a general rule will not grow from a leaf cutting. They will root but they won’t send up a new plant. There are only a couple of exceptions to that rule.
2. Rhizomatous (and Rexes):
Rhizomatous begonias will form plants from cuttings taken from any part of the plant. The easiest way is to root rhizome cuttings (stem cuttings) taken from the tips. You can also cut long rhizomes into one or two inch long chunks to root. These are best rooted by pressing into moist mix such as a peat moss/perlite mix leaving the top half of the rhizome exposed.
Put into a covered container under lights or in a warm shady spot. Rhizomatous begonias can also be started from leaf cuttings or even pieces of leaves. Smaller leaves or cut down larger leaves can be rooted in water. Leave two or so inches of stem on each leaf and put in small jars of water to root. When you see small plantlets start to form or at least some roots they can be potted into mix to continue growing. Bury the roots about half and inch to an inch deep whether little plantlets have started to form or not and within two or three weeks little plantlets will push up around the leaf.
Don’t worry about buringthe little plantlets but make sure to use a soiless mix such as a peat/perlite mix or they will rot and will have to reform. They can be separated later and put into regular mix or they can be left together to make a larger plant faster.
The leaf cuttings can also be rooted directly into peat or perlite in a covered container. Rhizomatous leaves can also be cut into triangular wedges with a vein in the center and rooted in peat or perlite. These will take a little longer to root but will produce more plants per leaf. Whenever rooting in an enclosed container make sure not to overwet the mix and make sure everything is as sterile as possible. (refer to growing seed articles for who to sterilize your containers).
Trailing begonias can be rooted exactly like the cane or shrub begonias but wait until after blooming if you want blooms on your plants since they are seasonal bloomers as a general rule. They make better plants if after rooting you put 3 cuttings into each pot to grow on and pinch the tips to make them branch.
Tuberous begonias can be rooted either like canes and shrubs or like rhizomatous. They will grow from leaves. Make sure to start cuttings early because they have to have enough time to form a new bulb before they go dormant in the fall. You can try rooting them under lights later in the year and growing them through the winter indoors. This will work with some varieties. Semi tuberous do not have to form a bulb and don’t go dormant so you don’t have to worry about starting them so early. These are usually only started from stem cuttings because they have so many stems that leaf cuttings aren’t neccessary.
Thickstemmed begonias usually start best rooting directly in mix. The stems are so thick and hold so much water that they usually rot when you try to root them in water unless you’re using small tip cuttings. Those root fine in water.
Credits / references:
Brad Thompson | Brad’s Begonia World