There are two types of branching that occur in trees and shrubs: alternate branching and opposite branching. With alternate branching, the side branches are staggered and alternate throughout the branch. The side branches grow directly opposite of each other in trees and shrubs with opposite branching.
There are far fewer trees with opposite branching than those with alternate branching, so this can be a big clue to the identity of the tree if you are trying to figure out what it is.
This also can help with shrubs, though more do feature this trait.
A mnemonic you can use to remember which genera of trees and shrubs do this is MADCap Horse. This will help you remember that they are:
- Maple trees (Acer)
- Ash trees (Fraxinus)
- Dogwood trees (Cornus)
- The Caprifoliaceae family, which are mostly shrubs and vines. Viburnums (which are sometimes classified now in the Adoxaceae family) and honeysuckles are familiar genera in this family.
- The horse is for horse chestnut. Members of the genus Aesculus include the horse chestnuts and buckeyes.
There are other shrub species that have opposite branching, like burning bush (Euonymus alata), winter creeper (Euonymus fortunei) and privets (Ligustrum spp.).