Methods for improving quality and conditions of ground cherry production

Methods for improving quality and conditions of ground cherry production

Summary

My project was designed to experiment with techniques to increase the viability of ground cherries as a fresh market and value-added crop, by improving harvesting conditions.  A combination of grafting, pruning, and trellising were used to create a more upright habit to improve harvest time and labor intensity, while a net trough was employed to catch the fallen fruit and eliminate ground contact.

Time, yield and quality data was collected twice a week during the harvest season, and the results were shared at the University of Maryland Eastern Shore Small Farm Conference, in November 2015.   I will also share results at a Specialty Crop Program at the Wye Research and Education Center, with Dr. Andrew Ristvey on December 8, 2015.

Objectives/Performance Targets

The third week of May, 2014, two 3’ wide x100’ long, raised beds were planted with Cossack Pineapple ground cherries at 2’ spacing, on black ground cover with drip irrigation.  This was one to two weeks later than planned due to very cool spring temperatures.  One row was grown as a control, with no intervention.  A second row was planted and had stakes driven every five feet, to support two plants between every set, and plants were pruned two weeks after planting, and twice after, in two week intervals.  The pruning created a more upright habit and allowed plants to be supported by using tomato clips to attach branches to twine. Prior to first harvest, the second week of July, crosspieces were attached to every other stake to make a “T” shape and a trough was created by cutting a 7’x100’ piece of insect netting lengthwise, and attaching it underneath the plant canopy, and to the crosspieces.  The netting was used to catch the fruit, eliminating contact with the ground, and making them easier to harvest.

The experiment, using the same plant stock, timeline and materials, was replicated at the Lower Eastern Shore Research and Education Center (LESREC), in their 3 acre organic plot.

Data on yield, time spent harvesting, and fruit quality was collected during the twice weekly harvests from both locations.

The intention was to have a third row planted with Cossack Pineapple ground cherries grafted to a root stock of Verde Puebla tomatillos, but the nursery who was commissioned to provide grafted plants had very poor germination, and the attempts they made at grafting a few of the plants failed.  It was unclear why their grafts failed, but poor healing chamber design was suspected, so upon notification that they would be unable to fulfill the order I asked to re-allocate funds so that I could build my own healing chamber and attempt to do the grafting myself.  I was able to successfully graft two plants, but the delay meant that they did not reach maturity in time to compare to the other treatments.  However, I did confirm that it is possible to graft ground cherries to tomatillos, which had never been done before.

Accomplishments/Milestones

Observations:

Ground cherries send many branches out laterally at ground level. Pruning to a single or double leader meant removing a large amount of the plant’s overall mass and resulted in lower yields at the onset of harvest.  It took about a month for yields from pruned plants to catch up with the control planting.

In spite of delay in production, the fruit caught in the net trough was of higher quality, especially after rain, than the fruit collected off of the ground. 

Pruning appeared to result in slightly larger fruit, with the average size of fruit from the pruned plants averaging 5/8”-¾”, compared to an average of ½”-5/8” from control planting.

The pruned planting at LESREC, though fruit was delayed at onset, remained healthy and produced vigorously until later in the summer than the control planting.

Collecting fruit from the net trough was significantly faster, and physically less demanding even when quantity was comparable.

The pressure from three-striped potato beetles was high at Calliope Farm, and we spent quite a bit of time monitoring for, and hand-picking bugs.  During the height of the growing season we lost about a quarter of the plants in the experimental row to defoliation, and by early September all of the plants suffered from significant bug damage.  Overall, the plants at Calliope yielded less than plants at LESREC.  However, even the lowest yielding plot produced enough to be economically worthwhile, and the correlations between experimental row and control row were consistent between the plantings at both locations.

Time spent laying ground cover, staking, stringing, pruning and hanging net, came to about 7 hours.  I think this time could be reduced by using wooden stakes instead of metal t-posts, and screwing the cross pieces on, rather than tying- this could be easily prepared in winter or early spring, and re-used for several years.  Also, the time and expense of ground cover could be reduced by using straw mulch.  While straw does not work well when harvesting the fruit off of the ground, if fruit were caught in the net, it should be fine.

Time and yield measurements were as follows:

Calliope Farm control row- 20.2 hrs: 158.15#

Calliope Farm experimental row- 7.65 hrs: 63.62 #

LESREC control row-  37.06 hrs: 242.91#

LESREC experimental row- 13.53hrs: 178.75#

• Fruit in Net
• First Pruning
• Ground Cherries on trellis
• GC with net trough
• Mature plants with net trough

Impacts and Contributions/Outcomes

While there were some negative effects, ie. delayed fruiting leading to diminished yield, of pruned ground cherry plants, I think that the practice holds promise.  The decrease in harvest time, improvements in the physical ease of harvest, and improvement in fruit quality would make continued experimentation to try to hasten yield volume worthwhile.  Even without improvements, it may be preferable to accept the diminished yield, and make up for it by increasing the size of the planting.

I have been contacted by other growers who learned about my experiment via the SARE website. I have shared my techniques and results via email so that they can replicate, or build on the knowledge gained, on their own farms.  Attendance to my session on ground cherries, tomatillos, and specialty crops, at the UMES Small Farm Conference was also strong.

Additionally, there has been interest from extension and faculty at several universities. I was contacted by Dr. Edward Durner, at Rutgers University to see if I would be interested in participating as a farmer/collaborator in a SARE proposal that he was invited to submit.  However, I believe his experiment focuses on the marketing of the fruit, rather than growing techniques.  I will also be presenting information at a small fruit crop program, with Dr. Andrew Ristvey, at the Wye River Research Facility in Maryland.

Sales at market, and to restaurants remained very strong this year, and the fruit was very popular among CSA members.

Collaborators: