By Susanne von Rosenberg, U.C. Master Gardener of Napa County
After you have been gardening a while, you may want to branch out and try growing more unusual plants. Being successful with less common plants requires more knowledge and research. Experience helps, too.
Uncommon plants fall into three categories. Some are simply unfamiliar but not difficult to grow, such as watermelons that don't have red flesh. (I like ‘Cream of Saskatchewan,' which has a creamy white interior.) We're all familiar with pluots (a 75 percent plum-25 percent apricot cross), but there are also plumcots (equal parts plum and apricot) and apriums (25 percent plum-75 percent apricot), as well as a cherry-plum cross. All of these crosses can thrive in Napa Valley, but be sure to check the basics before planting them. Does your microclimate provide enough hot days to ripen that watermelon, or enough chill hours for the aprium?
Other uncommon plants may be more challenging because you don't know anyone who has grown them. The jujube (also known as Chinese date or red date) is a fruit tree that at least one Napa County nursery offers in bare-root form. But do you know anyone who has grown one?
For such plants, you need to research the pros and cons yourself. Jujubes have spines on young wood, require unusual pruning techniques and tend to sucker. On the positive side, they thrive in almost any soil, are drought-resistant, have a long productive life (more than 50 years), often fruit within two years of planting and produce nutritious fruit.
Other plants may be rare in Napa County because they are difficult to grow here. They may not like our climate or need more day length than we have. While you can modify climate somewhat (depending on how much time and money you want to invest), there is little you can do about day length.
Plants from equatorial areas are used to a consistent 12 hours per day of sunlight and may not flower or fruit if the daylight period is longer or shorter. Chayote squash tends not to set fruit in Napa Valley until late August or early September, when the days are shorter, and then our growing season is cut short by frost before the squash have time to mature.
Before planting any uncommon plant, find out whether it is invasive in California. A few years ago, I became enthralled with a plant called autumn olive, also known as silver berry. Then I learned that it is considered invasive everywhere it is found. Even so, you can still buy it in nurseries, including on-line nurseries.
Next, think carefully about your microclimate. Consider how much sun or shade the plant requires, how much heat it needs or can tolerate and whether it requires some winter chill. Is the plant frost- or wind-sensitive? What are its needs with regard to humidity? What is its typical growing season, and is our growing season long enough for it to mature fruit?
What kinds of pests and diseases does this plant suffer from in its native habitat, and do we have any of these pests and diseases in Napa Valley? Make sure the plant can thrive in your type of soil and that, when full grown, it will fit in your garden. I was thinking about planting pecan trees until I learned that they typically grow 65 to 130 feet tall.
Finally, think carefully about how much time and money you want to invest. You could grow bananas in a heated greenhouse in our climate. Do you want to spend the money to install and heat a greenhouse?
Do your research using reliable sources such as the University of California Cooperative Extension, other university websites, information from U. C. Master Gardeners, reputable nurseries and other recognized authorities such as the California Rare Fruit Growers or California Native Plant Society. When considering information from other universities, be aware that their recommendations are based on the climate in that region.
Enjoy your explorations and let U. C. Master Gardeners of Napa County know what types of unusual plants you have growing in your yard.
The UC Master Gardeners of Napa County are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website (http://napamg.ucanr.edu) or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.