Question Answered by Amy Foreman, Botanist, GSS ESER Program
The lifespan of cacti vary widely depending on the species. Large saguaros, typical of the desert southwest, can live to be 200 years old. Many species of prickly pear, including those found in our local high desert plant communities, are thought to average about 20 years old. Living a long life helps increase the odds a cactus will successfully reproduce, but it’s not the only tactic cacti have evolved to spread.
Cacti can produce many thousands of seeds every year. They often have short-lived, but beautiful flowers which are pollinated by insects, birds, and bats. After pollination, flowers develop into fruit which contain seeds. At maturity the fruit of some species are sweet and fleshy with high water content. These fruit are attractive to animals that will consume them and disperse seed with their scat. The fruit of other species are dry and prickly, allowing them to disperse by attaching to animals’ fur. Only a few of the seeds produced from a cactus each year will find a suitable spot to germinate and establish another plant, making seed dispersal is a top priority for cacti!
Some species have an additional reproductive strategy – they can spread vegetatively. Our local prickly pear is an example of a species that is well adapted to spreading vegetatively. Its pads are connected by loose joints, which allow them to break off very easily. Once detached from the mother plant, pads can grow roots and begin a new plant. In fact, you can grow a prickly pear quite easily by (carefully) detaching a pad and burying the bottom inch or two in sandy soil.
One of the ways they propagate is by asexual reproduction. Asexual reproduction requires only one parent. Since there is only one parent, there is no exchanging of genetic information, and the offspring are clones of the parent. Asexual reproduction in plants can occur in a variety of forms, including fragments, runners, or tubers. Potatoes are a great example of a plant that can propagate by tubers. A tuber is a specialized root.
Materials: Potato with many eyes (small indentations on the surface of the potato), knife, toothpicks, clear container large enough to hold half of the potato
- With an adults help, slice the potato in half.
- Using toothpicks, suspend half the potato in the container with the fresh cut side of the potato facing the bottom of the container.
- Fill the container with water until most (not all) of the potato is below the water.
- Place the container in a sunny location.
- Check the potato daily. Don’t let the water go below about half the potato and completely change the plant’s water every few days.
- Wait until the eyes of the potato send out sprouts. When the sprouts become several inches long, transplant the potato to a container. Most potatoes take about a week for the sprouts to appear.