Tomorrow, the Santa Cruz Garden Exchange will have its last session for the season. The Exchange convened monthly during this year, providing opportunities for gardeners to share lots of surplus plants, plus some fruits, vegetables and garden pots.

Garden exchanges are a fine tradition for gardeners who find they have more plants than they want or need, don’t want to open a mini-nursery business, and can’t bear to discard healthy specimens.

The reciprocal benefit flows to other gardeners who enjoy receiving free plants that thrive in the local climate, and broadening their gardening experience with varieties they might not have encountered previously.

Some participants fill both roles, and can’t decide whether it’s better to give than to receive, or the other way around.

In this column, we explore the botanical context of the traditional garden exchange, where one might encounter many different plants.

Rarities

There are around 400,000 species of flowering plants (angiosperms), according to a team of botanists from around the world, including leaders from the Royal Botanic Gardens herbarium at Kew in London, and the Missouri Botanical Garden in St. Louis. A good number of these plants are considered rare, but that’s a subjectively defined category, and there are almost as many lists as gardeners. To check out the range of nominees, search the Internet for “rare plants.”

Plants are considered rare for various reasons: not yet discovered in the wild; discovered but not distributed by commercial nurseries; not garden-worthy (according to some arbitrary definitions); difficult to grow (this depends a lot on location); endangered as a result of human action, e.g., habitat loss.

Some gardeners seek rare plants for bragging rights or cultivation challenges.

Unfamiliar or Unusual

This category relates to the individual gardeners: what is unusual to one might be a favorite to another. This past week, I attended an expert presentation on Ariocarpus, which is a small genus of succulent, subtropical plants in the cactus family (Cactaceae). They grow in limestone hills in the south of Texas and the north of Mexico. These plants were certainly new to me, but a longstanding interest to the speaker and a few other members of the Monterey Bay Area Cactus & Succulent Society. We all learned these unusual plants are actually easy to grow when given acidic water.

The challenge of cultivating other unusual plants generally involves providing their native conditions. For example, I have been fascinated by Brazil’s giant rhubarb (Gunnera manicata), which has enormous leaves, and wanted to include it in my garden, but this is a plant that requires a lot of water. A local friend is growing it successfully, but he has an on-site water source.

Some mail-order nurseries offer unusual varieties, either as seeds or small plants, so adventurous gardeners will have little difficulty in finding something different. They might be pricey, but that’s part of the enterprise.

Familiar

We find this category of plants in local garden centers and most mail-order catalogs. We need not dwell on this category here, except to acknowledge that it represents the mainstay of residential gardens.

Pass-along Plants

These are the desirable plants often found in traditional garden exchanges. They are garden-worthy and typically very easily grown.

We could include a long list of plants in this category. Here is a typical list of pass-along plants:

• Daffodil
• Spider lily
• Canna
• Daylily
• Crinum
• Iris
• Camellia
• Gardenia
• Ginger Lily

Invasives

Our last category to consider consists of the overly zealous propagators. They are sometimes called “vigorous spreaders,” a polite term for plants that will take over your garden, when given a chance.  Many plants belong in this category, and they might show up in a garden exchange, so be on your guard. I once brought home an attractive succulent plant identified as a Bryophyllum. Something new! When I searched for it on the Internet, however, I discovered that its common name is “Mother of Thousands,” and a closely related plant is called “Mother of Millions.” I did not add that plant to my garden.

The Santa Cruz Garden Exchange will occur at 8:00 a.m., Saturday, October 27, 2018, at the Live Oak Grange Hall, 1900 17th Ave. Santa Cruz. The available plants (all free) will include a good supply of high-quality iris rhizomes, to be planted soon so they could establish roots during the coming rainy season. This is the last opportunity this season to participate in this great tradition for home gardeners. Arrive early!