Sometimes horticultural myths aren’t exactly wrong, it’s just that they add an unneeded complication to what should be simple. Such is the case for the belief that you should always make stem cuttings (and also leaf cuttings) at a 45° angle. This is often said to stimulate rooting or to allow the stem or leaf to better absorb water.
Many gardeners firmly believe this, largely because they were always told to do it. In fact, this information does indeed appear in many of the most popular gardening books and on many websites, but it’s simply an old belief that has no particular foundation.
The reality is that you can take cuttings at almost any obtuse angle: 45°, 60°, 90°, etc.
There is, however, a limit to cutting at too narrow an angle. Very acute angles, say 25°, will leave the very tip of the cutting only a cell or two thick and therefore very fragile. This could easily lead to rot setting in … rot that could spread to the rest of the cutting and that’s not something you want.
Personally, I usually take my cuttings at about a 90° angle simply because … it’s faster that way. When you try to make high-precision cuts, you waste too much time!
To learn more about how to take and root cuttings, read Rooting Cuttings Step by Step.