Vegetative spread

**Vegetative spread** or **asexual reproduction** is the process by which plants spread by creating *clones* of themselves - as distinct from sexual reproduction, in which plants of the same species create genetically distinct new plants by combining their DNA. If you plant a seed, you are helping a plant species reproduce *sexually*, but if you plant a cutting, you are helping the species spread *asexually*. Most plants utilize both sexual and asexual reproduction.

Weedy plants, including some of the more common invasives, are often experts at the use of vegetative spread, which can make them extremely difficult to eradicate. A single Japanese knotweed plant that was brought to London's Kew Gardens in 1850 has now spread - entirely asexually - across all of England and Wales. (This is due partly to the plant's own remarkable properties - a root cutting the size of a fingernail is large enough to grow a new plant - and partly due to human land use patterns, particularly the way we transport and reuse soil dug up during construction.) But, since both invasive and beneficial plants use the same techniques, it's equally important to know how native plants spread as well.

## Methods of Vegetative Spread

### Tillers, rhizomes, and stolons

Some plants, particularly grass plants, spread vegetatively by creating additional stems. There are three basic types of new stem: **tillers**, **rhizomes**, and **stolons**.

A **tiller** is a new vertical stem which emerges from the existing plant's crown. Tillers do not appear at a distance from the existing plant - rather, the plant crown grows wider and denser. Each new tiller is an independent clone, capable of creating its own root and shoot system. All grasses spread by producing new tillers, but not all grasses use *only* tillers to spread.

A **rhizome** is a specialized stem which spreads horizontally *below* the soil. At a certain point, the rhizome will emerge above the surface, creating a new clone of the existing plant. The new plant will emerge at some distance from the original, and - because the rhizome is underground - the new plant will look like it appeared from nowhere. This new clone will develop its own crown and roots and will grow independently, ultimately creating new rhizomes. Golden bamboo (*Phyllostachys aurea*) is an example of an aggressive rhizomatous plant that can only be controlled by controlling its rhizomes (e.g. with a rhizome barrier).

A **stolon** is a specialized stem, often called a "runner", which spreads horizontally *above* the soil. Like rhizomes, it can create a new plant at some distance from the original - though the gardener can, at least, follow the connection - and the new plant can itself create even more stolons. The garden strawberry (*Fragaria ×ananassa*) is an example of a stoloniferous plant; a single strawberry plant may create as many as 30 to 50 runners, creating a dense mat of plants.

## References

1. ↑ Grabar, Henry (May 9, 2019). "Oh, No, Not Knotweed!" *Slate*. Retrieved June 3, 2019.
2. ↑ 2.0 2.1 2.2 Chastain, Thomas. "Tillers, Rhizomes, and Stolons". *Seed Production*, Oregon State University. December 24, 2013.
3. ↑ Missouri Botanical Garden. "Controlling Bamboo". Retrieved June 3, 2019.
4. ↑ Mr. Strawberry. "What Are Strawberry Runners? (Stolons)" *Strawberry Plants.org*. June 18, 2018.