Herb, shrub, tree: growth forms of plants

The realm of plants is quite varied. There are tender green stems as well as thick trunks that can reach over a hundred meters into the sky. In this country, most plants grow herbaceously, as shrubs or trees. To find out what this means, let’s take a closer look at the different growth forms.

A first orientation

If you look at the different plant families in the vegetable patch and orchard, you quickly realize that even the individual representatives of a family can sometimes differ quite a bit from each other. The rose family serves as a good example: some species grow as shrubs like the raspberry, others as trees like the apple. And the strawberry? That must be some other kind of green plant.

Very roughly, we can distinguish between herbaceous and woody plants. Woody plants are also called woody plants, and include shrubs, trees, and lianas. Herbaceous plants, however, are not called herbs, since this term already means something else. Many herbs are herbaceous plants, but some are also partially woody in the lower part (rosemary, thyme, sage…); they are then called semishrubs. So the exact border between “herbaceous” and “woody” is often not so clear.

Herb, shrub, tree: growth forms of plants
Semi-shrubs in the herbaceous bed: woody below, herbaceous above

Herbaceous plants: green behind the ears

All plants grow both in height and width. Accordingly, this is called height and thickness growth. Herbaceous plants also exhibit more or less pronounced thickness growth, but they all do not get beyond a certain “thickness”. They do not start so-called secondary thickness growth, which would gradually give the stems a woody, firm structure. So their shoots tend to remain soft and unstable. However, this does not necessarily mean that herbaceous plants are fragile – they can certainly live for several years.

Examples of annual herbaceous plants are corn, lettuce, or cucurbits. They die in the fall once they have formed their seeds. Some plants are cultivated as annuals in our climate, although they could grow older under other conditions, e.g. the tomato.

Herb, shrub, tree: growth forms of plants
The thick stems of zucchini can form imposing tower-like structures, but in the fall the plant dies

Biennial herbaceous plants do not die in winter and accompany us for two garden years. Examples are carrots and fennel, which are usually harvested in the first year, but would not bloom until the second year. Leeks, parsley and cabbage are also biennials. All of these plants need the cold of winter for their seed formation the next year.

Perennial plants, as their name suggests, live for several years. But watch out, here’s where it gets confusing: strawberries also live for several years, but botanically they are not considered perennial plants because they flower and bear fruit every year. Perennial plants, in the botanically correct sense, bloom only once and then die. However, they do not occur in our vegetable beds and orchards.

So the strawberry is perennial in the colloquial, horticultural sense. The botanical term is perennial. Perennial herbaceous plants are called perennials.

Herb, shrub, tree: growth forms of plants
Strawberries are also called permanent crops, because they grow in the same place for several years.

Woody plants: beautifully stable

Woody plants are all perennial. That is, they both live for several years, and also usually bloom and fruit every year. In this category, we distinguish between the semishrubs, shrubs, trees and lianas.

Semi-shrubs

Semi-shrubs don’t really know what they want. Or maybe they combine the best of herbaceous and woody plants: fresh green on top and nice and sturdy underneath? In any case, they are somewhere between these two growth forms. Typical examples are thyme, rosemary, lavender or sage, which become increasingly bare and woody at the bottom over the years. Regular pruning can counteract this somewhat and encourage the plants to grow bushier.

Raspberries or blackberries also grow as half-shrubs, although they do not participate in the horizontal division “wood at the bottom and green at the top”. All shoots eventually become completely woody over the years. However, since the plants form completely fresh, new shoots every year, they are, so to speak, vertically divided into herbaceous and woody.

Shrubs

Shrubs are characterized by the fact that they do not have a “main stem”, but many individual stems that continue to branch. In addition, new woody shoots sprout again and again near the ground. There are small and rather stocky shrubs, but also very tall ones. Many species are well suited as woody plants for a hedge.

By the way, shrub and bush mean the same thing, although one speaks of a bush when a shrub grows round – bushy.

Trees

We all know what a tree is… but for the sake of completeness, here is some interesting information. With the tree we come back to the term secondary thickness growth. All lignifying plants show this, but the mighty trunk of a tree with all its annual rings is probably the best example. Every year, during each growing season, the trunk forms a new layer that lignifies over time. If you cut the trunk into slices, you can count these layers and know exactly how old the tree was.

However, a tree also grows imposingly in height and branches quite high up. The branches in the tree crown also grow thicker from year to year and sprout new growth at their tips.

In most plant families, trees also occur as a growth form. However, in some families from our gardens, all of which we present in an extra article, trees are not members: in the allium, cucurbit, foxtail, and umbellifers.

Let’s take a brief look at some other terms. Besides the natural growth forms of plants, there are also cultivated forms. In the case of a tree, for example, a distinction is made between how tall it grows and the height at which its crown begins. An apple tree can be bred for the private garden in such a way that its crown begins quite far down – practically for an easy harvest, one speaks then of a half trunk. Higher crowns, on the other hand, are needed if you cultivate an entire orchard and need to mow under the trees. Still other cultivars are found in apple orchards, where the trees grow as columns or spindles. The advantage: many apple trees in a small space.

Vine

Liana sounds like jungle and tropical jungle, but in fact the term is also used as a growth form for plants that thrive in our country. They are characterized by the fact that they have a woody stem and grow up scaffolding, house walls or, of course, other plants. In the process, they climb with the help of shoots or wind upward in a circle. The best known representative in this country is probably the vine: entire house walls can disappear under its foliage if it is not cut back. Wild vine often climbs trees.

Botanically, by the way, peas and runner beans are also lianas. This is somewhat confusing since they are also described as herbaceous. The distinction here is not entirely clear. Blackberries can also grow as lianas in the wild, forming long shoots that can travel to high treetops. But don’t worry, our Bloomify Blackberry grows well-behaved as a non-vining semi-shrub.