By Michael Brown
Farmers are always looking for the next new product to entice their customers and expand sales. Physalis is one of those crops that might be worth considering. Physalis is a genus of flowering plants in the nightshade family, which also includes tomatillo and is more distantly related to peppers, tomatoes and potatoes. They grow in warm temperate and subtropical regions of the world, primarily in the Americas. One of the most notable features of the genus is a thin, paper-like husk that encloses the fruit. Farmers and consumers are most likely to be acquainted with them as ground cherries.
Carol Mucher, garden director at the NB Community Harvest Garden in New Brunswick, Canada, has been growing ground cherries for a number of years. “They go over very well with our customers,” she says. “Parents usually send their kids foraging for the fruit because the plants are quite low to the ground and the fruit tends to fall from the plant.”
This more or less sums up the general situation with ground cherries — attractive to customers but not very easy to harvest. This attractive fruit (Physalis pruinosa), encased in a paper-like husk, is usually grown by farmers in relatively small quantities and can be found at farmers markets or as part of a CSA share. Occasionally the fruit, mostly from South America, will be available in larger supermarkets.
The ground cherry’s big brother, sometimes referred to as goldenberry (Physalis peruviana), is much less frequently grown. Growers are hampered by lack of reliable information on best growing methods, confusion about suitable cultivars and lack of reliable sources of seed. That may be about to change.
HortFarm 3 in East Brunswick, New Jersey, is a short drive from Rutgers University in nearby New Brunswick. The expansive fields are home to a variety of fruit, nut and vegetable trials aimed at increasing the choices for New Jersey farmers and determining best growing practices. Here, on two acres, among hot pepper and hibiscus trials, is the largest planting of goldenberry on the East Coast.
Dr. Ed Durner, a professor at Rutgers, has been trialing goldenberry for the last several years, with the goal of identifying promising strains and creating production guidelines for farmers interested in exploring this tasty and nutritious fruit. Dr. Durner recently received a grant to help introduce this plant to farmers with CSAs and farmers markets in the Northeast.
When I first started reading about ground cherry and goldenberry, it quickly became apparent that there is pervasive confusion between the two main species — Physalis pruinosa and Physalis peruviana. One of the first goals of understanding the choices available to growers is getting the nomenclature correct.
The fruit commonly referred to as ground cherry, cape gooseberry or goldenberry (among many other names) actually consists of two different species — Physalis pruinosa and Physalis peruviana. The confusion begins in seed catalogs, and in the literature in general, when referring to these two varieties and assigning them common names. In fact, in the literature Dr. Durner distributes to growers, he lists over 40 common names for the two species.
For this article, I will be referring to the Latin names for better clarity. Following are very basic descriptions of how they differ and the most common name as reference. One note: In the literature, “cape gooseberry” is referred to as both P. pruinosa and P. peruviana. I am therefore sticking to the terms ground cherry and goldenberry.
P. pruinosa – ground cherry: prostrate, spreading plant with approximately ½-inch fruit that falls from the plant when ripe.
P. peruviana – goldenberry: large, upright plant (4-6 feet) with approximately ¾-inch fruit. Fruit must be pulled or cut off the plant.
Seeds should be lightly covered with soil or some other planting medium. Optimum temperature is around 85 degrees Fahrenheit, but a range of 75-90 degrees Fahrenheit is safe. Temps below 65 and over 95 will significantly delay germination. Seeds should germinate in 2-6 weeks. Seed should be started early, around the same time as peppers or tomatoes, and planted outside after the temperature warms.
Physalis is native to South America and so needs to be treated as an annual in temperate regions, as with tomatoes or peppers. Though seedlings can withstand a light frost, they will be damaged by temperatures below 30 degrees F. Production is best on well-drained, “poor” soils. Plants are not drought tolerant and growth and production will be compromised without consistent irrigation. It is therefore important to emphasize that both P. pruinosa and P. peruviana may not be good candidates for dry field growing. Development and ripening of fruit will be significantly impacted without consistent irrigation of about an inch a week.
Fruit is ripe when it turns a golden color, which is usually visible through the husk. At the time of ripening the husk will be yellowish-brown and translucent. Fruit will not continue to ripen after harvest, so an effort should be made to pick fully ripe fruit. Fruit should be picked dry, as moist fruit tends to get mold. Fruit left in the husk will keep at room temperature for up to three months. Good air circulation also helps prevent mold. This eliminates the pressure of selling fruit immediately before it spoils.
P. pruninosa starts to fruit after about 75 days from transplants. P. peruviana needs a much longer season of about 120 days, and so plants started inside in New Jersey (zone 6b) in late March will start producing fruit around the end of August.
The most serious pest of Physalis is the 3-lined lema beetle, also referred to as 3-striped potato beetle (Lema trilineata). Andrew Ristvey, researcher at the University of Maryland, has also identified hornworm (Manduca species) as a pest on some P. peruviana plants.
Pros and Cons
P. peruviana: One of the main drawbacks of P. peruviana seems to be the long growing season required before fruits can be harvested. Production of fruit can also be somewhat moderate. In addition, reliable sources for seed are limited. Some of these issues are being addressed by Dr. Durner in his trials.
An advantage of P. peruviana is that the plants are larger and more upright and that the fruit does not abscise when ripe, giving more control and easier conditions (not stooping on the ground) for harvesting. On the other hand, because they don’t abscise when ripe, they must be cut off the plant, which makes harvest more time consuming.
P. pruinosa: Ground cherry gives the grower a much longer harvest window and seems to be more productive than P. peruviana. There is also ample and varied sources of seed, though there is little documentation about specific differences between varieties. The major disadvantage of P. pruinosa is the very low, sprawling habit of the plant, which makes harvest difficult.
Mike Brown is the owner of Pitspone Farm — a small-acreage berry farm and nursery in central New Jersey.