Stems and propagation

Stems often are used for vegetative plant propagation. Using sections of aboveground stems that contain nodes and internodes is an effective way to propagate many ornamental plants. These stem cuttings produce roots and, eventually, new plants.

Below-ground stems also are good propagative tissues. You can divide rhizomes into pieces; remove small bulblets or cormels from their parent; and cut tubers into pieces containing eyes and nodes. All of these tissues will produce new plants.

Types of plants and their stems

Trees generally have one, but occasionally several, main trunks, which usually are more than 12 feet tall when mature. In contrast, shrubs generally have several main stems, which usually are less than 12 feet tall when mature.

Most fruit trees, ornamental trees, and shrubs have woody stems. These stems contain relatively large amounts of hardened xylem tissue in the central core (heartwood or sapwood).

Herbaceous or succulent stems contain only a little xylem tissue and usually live for only one growing season. In perennial plants, new herbaceous stems develop from the crown (root-stem interface) each year.

Canes (Figure 9a) are stems with relatively large pith (the central strength-giving tissue). They usually live only 1 or 2 years. Examples of plants with canes include roses, grapes, blackberries, and raspberries. For fruit production, it is important to know which canes to prune, how to prune them, and when to prune them.

A vine (Figure 9b) is a plant with long, trailing stems. Some vines grow along the ground, while others must be supported by another plant or structure. Twining vines circle a structure for support. Some circle clockwise (e.g., hops and honeysuckle), while others circle counterclockwise (e.g., pole beans and Dutchman's pipe vine). Climbing vines are supported either by aerial roots (e.g., English ivy and poison ivy), by slender tendrils that encircle a supporting object (e.g., cucumbers, gourds, grapes, and passionflowers), or by tendrils with adhesive tips (e.g., Virginia and Japanese creeper).

Stems as food

The edible portion of several cultivated plants, such as asparagus and kohlrabi, is an enlarged, succulent stem. The edible parts of broccoli are composed of stem tissue, flower buds, and a few small leaves. The edible tuber of a potato is a fleshy underground stem. And, although the name suggests otherwise, the edible part of cauliflower actually is proliferated stem tissue.