A plant's stem consists of nodes and internodes. A plant node is the area from which leaves grow. Nodes are also the location of buds that can grow into branches and aerial roots. The space between nodes on a stem is the internode. Locating the nodes of a plant is important when you are doing regular maintenance such as pruning, and also when you propagate plants from stem cuttings or grafts.
The base of a bud, leaf, twig or branch is always attached to a node, so this is one easy way to find them.
Even without visible buds or leaves, you can tell where the node of a twig is by some signs that you only see at a node:
- a scar in the wood where a leaf has fallen away
- a knob-like, slight fattening of the wood (think of a bamboo cane)
- solid nodes in plants with hollow stems such as forsythia, smooth hydrangea, and bamboos
By contrast, internodes are the sections of stem between nodes. If the nodes are the crucial “organs” of the plant, the internodes are the blood vessels carrying water, hormones and food from node to node.
Usually, internodes are lengthy and provide spacing between nodes of several inches. However, some plants are notable for how close together their leaves, and thus their nodes, always are. Dwarf conifers have closely spaced nodes. Yews and boxwoods, with their dense leaves, also always have short internodes. This fact is why they can be sheared or pruned into any shape, including special forms of topiaries.
Importance of Nodes in Pruning
Whether you are new to pruning, or just intimidated by it, locating the node is an important step in the pruning process.
- Always prune just above a node on a stem. The dormant buds in the node will grow out into new stems. If you cut below a node, you leave a section of stem (the internode) that cannot grow stems. It is prone to rotting and becoming susceptible to diseases that can kill your plant.
- Prune above nodes with buds that face away from the center of the plant. The new growth will grow in that direction, leaving the center open to air and light. This prevents diseases and pest infestations. This also works well when you are shaping a plant. For example, when pruning roses, prune back nodes that are facing outward to promote a nice, open shape to the plant.
Importance of Nodes In Propagation
Many types of plants, both woody and herbaceous, can be propagated by stem cuttings, a process that yields a plant identical to its parent. A 6-inch or longer cutting is taken from the parent plant for rooting in soil. For successful rooting, make the cut immediately below a node, which is the area that will produce the roots. The cutting also needs a terminal bud or another node above the soil line for new growth.
Nodes in Grafting
In contrast to pruning, often you want to make cuts for grafting not near nodes, but right through the center of an internode. In the whip and tongue graft, for example, careful cuts need to be made along the grain of the wood. If you were to make these cuts through the thick, knobby nodes, they would not be straight and the graft union would fail.