Buds, nodes, and growing points

Picture the trident maple, one of this course's instructional example trees, in late winter. One shoot has grown long and straight, and you would like it shorter. The obvious question is where to cut. A more useful one comes first: after the cut, what will be left that can grow?

A tree cannot start a new branch anywhere it likes. New shoots grow from growing points it already has, which on many trees you can see right now, or, on some trees, from new buds it forms on older wood. Read a twig closely and it shows you what a cut would leave behind.

The parts of a shoot

A shoot is a stem with its leaves, built in a repeating pattern. The place where a leaf attaches is a node. The bare stretch of stem between one node and the next is an internode. Internodes carry no leaves and no buds of their own, so on a young stem, new shoots start at the nodes.

Look at a leaf where it meets the stem. The angle on its upper side is the leaf axil, and in that angle sits a small bud: a compact, undeveloped shoot, flower, or both, often wrapped in protective scales. A bud on the side of the stem like this is a lateral bud, also called an axillary bud. At the very end of the shoot is the terminal bud, or apical bud, which continues the shoot's growth in length.

That gives you a dependable rule of thumb: wherever a leaf is attached, a bud usually sits directly above it. Find the leaves and you have found the buds. On many trees, though, including cherries and elms, some buds hold only flowers, and a flower bud will not grow into a branch.

Internodes tend to be longer on fast-growing or shaded shoots and shorter on slower growth in strong light. Short internodes fit more nodes, and so more possible branches, into a small space, which is one reason bonsai growers value them.

Opposite or alternate: how many shoots, and which way

In an opposite arrangement, two leaves grow from each node on opposite sides of the stem, each with a bud in its axil. Maples, including the trident maple, grow this way. Each pair usually sits at right angles to the pair below, so on a real twig the buds point in four directions. A cut immediately above a node often produces a pair of shoots, one from each side.

In an alternate arrangement, each node has one leaf and one bud, and the next node's leaf is on a different side; on many trees the leaves spiral around the stem. Beeches, elms, and the ficus all have alternate leaves. A cut immediately above a node usually leaves a single bud at the top, so new growth tends to come singly.

Either way, a new shoot tends to start out in the direction its bud points, before it turns upward and toward the light. A bud on the outer side of a branch tends to send a shoot outward; a bud facing the trunk tends to send one inward.

Reading a twig in winter

When a deciduous tree drops its leaves, the pattern stays readable. Where each leaf fell, it left a leaf scar, often a crescent or shield with tiny dots where the leaf's veins passed through. The bud that formed in that leaf's axil sits directly above the scar, so the scars lead you to nodes and buds even when the buds are tiny.

Farther down, look for a band of fine, crowded rings around the stem. These bud scale scars mark where a bud's protective scales fell away as it opened, and so where a burst of growth, or flush, began. On a tree that flushes once a year, each stretch from one band to the next, or to the tip, is one season's growth, so you can count back through recent years; a tree that flushes several times a year leaves several bands in a year.

In Read a twig, press Start at the tip and step through the parts with Next. Then switch Twig to Alternate, a shoot still in leaf, and find the bud in each leaf axil. When you can name every part, try Count the years.

On both twigs, every bud sits at a node, above a leaf or leaf scar, never partway along an internode: one per node on the alternate twig, two on the opposite one. The stretches between bands differ too: the maple-like twig grew its longest stretch two seasons ago and a much shorter one last season, a record of how the tree has been growing.

Where new growth comes from

Buds matter because of what is inside them. Under the scales of a terminal bud lies a shoot in miniature: tightly folded young leaves around the apical meristem, a small zone of dividing cells at the shoot tip. In Lesson 2 you met a meristem at each root tip; this is the shoot's version. As the shoot grows, the apical meristem makes new stem, nodes, and leaves, and a new bud forms in each leaf axil along the way.

Each lateral bud holds its own small meristem. Some grow into side shoots in their first season; many wait. A bud that stays inactive for years is a latent bud (growers sometimes say dormant bud, though any bud resting through winter is dormant). On older wood it can lie hidden beneath the bark, still alive, and after a disturbance, such as losing the shoot beyond it, it may grow.

Some trees can also form an adventitious bud: a new bud where none existed before, such as in the new tissue around a wound or on older wood. This ability varies greatly; some trees do it readily, others hardly at all.

So new shoots come from meristems in buds and shoot tips; these are a tree's growing points. The vascular cambium from Lesson 3 is a meristem too, but its main work is to thicken a branch, not to make the buds along a shoot. A stretch of branch with no buds, no foliage, and no ability to form new buds has no way to grow a branch, however healthy the rest of the tree is.

Conifers: growing points in the foliage

On broadleaf trees such as the trident maple and the ficus, buds usually sit plainly along the stem. Many conifers are different. On a juniper, the growing points sit at the tips of the shoots and within the foliage itself, small and hard to see, rather than as distinct buds spaced along a bare stem.

What happens on bare wood matters even more. Many conifers, including most junipers and pines, rarely produce new shoots from bare, older wood. On a dense nursery juniper, foliage often grows only at the outer ends of the branches: the inner stems, shaded by the growth outside them, lost their own foliage long ago, and their growth options went with it.

Not every conifer behaves this way: yews often regrow well from old wood, and broadleaf trees differ among themselves too. “Conifer” or “broadleaf” alone does not tell you how a tree will respond to a cut.

What a cut keeps and what it removes

While a shoot tip is actively growing, it tends to hold back the buds below it, an influence called apical dominance that Lesson 12 explains. Remove the tip, and one or more of the buds nearest the cut often grow instead.

Which buds grow, and how strongly, depends on the tree's vigor (how strongly it is growing compared with what is normal for its kind and the season), the season itself, the light reaching the buds, and the tree's own budding behavior. A cut changes the odds; it does not issue orders.

What grows after a cut? tests this on two branches, drawn in leaf during the growing season. With Tree behavior on Buds readily on older wood, choose Position 3, on last year's leafless wood, and read what stays below the cut. Before you press Show likely response, find the growth the cut would keep. Then try Positions 1 and 5. Finally, switch to Rarely buds on bare, older wood: Position 3 is the cut from the juniper question, and Position 4 keeps a little foliage.

On the maple, Position 5 keeps leaves that go on making sugars for the new shoots. Positions 1 to 3 leave a leafless stub, so any shoots there grow at first on stored reserves (Lesson 9). At Position 3, the visible pair of buds is likely to grow. At Positions 1 and 2, only latent buds remain, so shoots are possible, not promised; if none grow, the stub may die back. On the juniper, Position 3 is close behind the green but keeps no foliage and no growing points, so that section may die back; Position 4 keeps foliage, and growth continues.