Summer and Winter Squash Research and Breeding for the Southeast

Progress report for FS23-347

Project Type: Farmer/Rancher
Funds awarded in 2023: $20,000.00
Projected End Date: 03/31/2025
Grant Recipient: Common Wealth Seed Growers / Twin Oaks Seed Farm
Region: Southern
State: Virginia
Principal Investigator:
Edmund Frost
Common Wealth Seed Growers / Twin Oaks Seed Farm
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Project Information


Research, breeding, selection and seed production work with squash in the Southeast has the potential to improve the pest resistance, disease resistance, quality and productivity of varieties available to Southeast growers.

In this project we will research several kinds of summer and winter squash, with goals of identifying existing varieties that are better suited to Southeast conditions, and of creating new ones. We are seeking varieties that thrive, produce, and keep well in our hot, humid weather and can withstand the pest and disease pressures we experience here. They should also have good eating quality and be easy to manage and harvest. 

With summer squash our research will take the form of variety trials in 2023, and then follow-up breeding and variety trials in 2024. In 2024 we will also do seed production of trial standouts in pollination cages. We will be trialing both Cucurbita pepo and Cucurbita moschata varieties.

With winter squash, where we already have done many years of research and breeding work, we will focus on testing the feasibility of using pollination cages with introduced bumble bee pollinators for C. moschata squash seed production, as well as on continuing selection and comparison of existing breeding lines. We have already developed and released downy mildew resistant varieties South Anna Butternut and Xiye Butternut, and have identified, improved and released several additional varieties. With access to more isolation plots we are on track to release additional varieties, with better keeping quality and other useful traits (see below), in the next 1-2 years.

Using screen cages could also be an important element of maintaining the USDA moschata collection. Our project aims to model their effective use for moschatas in our region, and will give us needed experience to work on (and help others work on) regenerating the USDA moschata collection in the future.

We are in contact with growers who have used pollination cages for seed crop isolation in other regions, including Louisa Brouwer of Ferry Boat Seeds in Washington, Jay Bost (who used screen cages in Hawaii and has recently moved to North Carolina), and Micaela Colley of Organic Seed Alliance in Washington. We will also be referring to a project on screen cages from Hawaii: “DIY Screen Cages for Insect Management in the Tropics.”

We are not however aware of growers who have used screen cages for cucurbit crops in the Southeast, or for moschata seed production. So while we have several models to draw from in making screen cage growouts successful, we also expect to demonstrate and trouble-shoot something new for our region.

The new winter squash populations at Twin Oaks were developed mainly in breeding trials that were part of our 2020-2021 SSARE producer grant “Breeding and Evaluation of Butternut Squash Varieties for Southeast Organic Farms.” We also followed up on that research in 2023 with unfunded breeding trials.

More about the populations we’re working with at Twin Oaks:

-75% South Anna Butternut, 25% Chinese Tropical Pumpkin (F4). A butternut with good keeping quality, productivity, eating quality and sweetness. The flesh has finer texture than South Anna, and larger seeds. In 2022 we grew 20 F3 plants and obtained self-pollinated seed from several promising selections that we intend to recombine, in large-fruited and a small-fruited groupings, each in its own isolation cage. The advantages of this population over South Anna are better keeping quality, potentially better yields, and more uniform fruit sizes.

-‘Butternut 200’ (75% South Anna and 25% JWS 6823) (F5). This comes from a 2020 breeding trial selection. It is a small butternut with excellent nutty flavor and fine texture we think could be competitive with ‘Honeynut’ as a high quality niche variety, but has the added advantage of good downy mildew resistance. The small size is desirable for market and CSA growers. In 2022 we observed variation in productivity between plants, but obtained hand crosses between more productive plants. Productivity and keeping quality may not be optimal for this seedstock, but we believe there is room for fine tuning. For isolation cage in 2023.

-South Anna x Guatemalan Green Ayote F4; and South Anna (62.5%) x Guatemalan Green Ayote (25%) x JWS 6823 (12.5%) F3. These populations come from selections made in our 2020 breeding trial that we crossed together. Fruits have excellent keeping quality, good productivity, fine to medium texture, small seeds, and good flavor, dry matter and sweetness. Exterior coloration is diverse - some retaining green or green-orange stripes when ripe, while others have standard butternut color. Stands out for keeping quality. We will likely hand pollinate these to isolate different colors.

-Chinese Tropical Pumpkin. A variety derived from Crowning F1, with excellent flavor and productivity. Mostly flat ribbed pumpkins, but there are necked offtypes we want out of the population. We made progress in 2022 by crossing three good plants to each other. But we want a broader genetic base, so we’ll self pollinate more good plants in 2022.

-Moranga Coroa x Winter Sweet F4. A cucurbita maxima variety we are breeding for vine borer resistance and rich kabocha-type flavor. Excellent keeping quality, and some with excellent flavor, but needs to be stabilized for flavor. For self pollination in 2024

At Care of the Earth Community Farm we are working with populations derived from a cross between Waltham butternut and a Costa Rican variety called San Jose Mountain Club. The original goal was a good tasting butternut with resistance to downy mildew, black rot, and bacterial wilt – which were all serious problems for butternut crops at the farm. We have released Xiye as a variety, though it is still in need of refinement. It has good disease resistance, eating quality and productivity, and has proved a valuable part of Care of the Earth’s CSA production. It is more determinate than South Anna. Fruit size and shape needs stabilization. We also have another selection from this population - with small fruit and shorter vines. It needs further evaluation and stabilization. Our 2020-2021 SSARE grant also contributed to this population’s development.

Project Objectives:

Summer Squash

We are proposing two summer squash research efforts, one with C. pepo squash at Care of the Earth Community Farm (where vine borer pressure is not present), and the other with C. moschata squash, at both Twin Oaks Seed Farm (where vine borer is present) and Care of the Earth Community Farm.

We are aware of nine varieties of C. moschata summer squash: three from Korea, two from Brazil, three derived from the Italian variety ‘Tromboncino,’ and one from Veracruz, Mexico. The Korean squashes are listed as hybrids, and one is only available with treated seed, which we can’t use on our organic farms. Altogether in 2023 we will screen eight C. moschata summer squash seedstocks at Twin Oaks Seed Farm in year one, in two successions so that we can better understand the difference between early and late season needs. One variety will be replicated three times in each succession to confirm field uniformity. One succession of these same moschata varieties will also be grown and evaluated at Care of the Earth Community Farm. Each plot will have five plants, with a total of 180 row feet per succession. We don’t know how vigorous the vines are with many of these so will give them extra space.

In the 2023 C. pepo summer squash trial at Care of the Earth Community Farm we will screen 13 varieties (including 4 varieties from Mexico, 6 open-pollinated varieties currently cultivated in the Southeast, and 3 hybrid controls - Elite, Gentry, and Respect - that were standouts in trials at LSU and UGA). Gentry will be replicated three times to confirm field uniformity. This will be planted in two successions so that we can better understand the difference between early and late season needs. Each plot will have five plants, with a total of 200 row feet for each succession.

In the summer squash trials we will measure yields; rate the impacts of diseases including downy mildew, bacterial wilt, and yellow vine disease; rate damage caused by vine borers and other insect pests; and assess eating quality, fruit shape, plant architecture and determinacy. In the second succession of both the pepo and moschata trials, we will be doing some hand-pollinated crosses between varieties that stood out in the first succession, as well as saving hand-pollinated F2 seed from any standout F1 hybrid varieties – this will set ourselves up for selection work the following year.

In the 2024 summer squash trials we will dedicate 300 row feet to follow-up summer squash breeding and variety trials. This will include advancement and evaluation of F1 crosses made in 2023; evaluation and selection from F2 populations derived from crosses made in 2023 and increased early in the year in 2024 in a greenhouse; and evaluation and selection from F2 populations derived from commercial F1 hybrids; as well as any comparison of varieties that may be needed to confirm or expand 2023 findings.

Winter squash

At both Care of the Earth Farm and Twin Oaks Seed Farm we have been working on developing new winter squash varieties (mostly butternut) for several years.

In 2023 at Twin Oaks Seed Farm we will grow three promising new winter squash populations in screen isolation cages. The purpose of this is to test the suitability of screen cages with introduced pollinators for producing moschata squash seed in our region; to save selected seed from each of the populations; and to evaluate the populations, comparing them to each other. Plants within each plot will be allowed to intertwine, but then fruits will be traced back to the plants they come from, and each plant (and each plot as a whole) will be evaluated for yield, keeping quality, eating quality, and appearance. Disease and pest pressure will also be evaluated (screen cages will not be put in place until just before flowering so there will be a chance to assess insect pest pressure). This method will allow for ongoing maternal selection of the seedstocks. We will also evaluate seed quality and measure seed yield. Each 50x14 screen cage will have 15 plants spaced at 2.5 feet. We are expecting that some of these will become named varieties, ready to sell at the end of 2023 or 2024. In addition, outside the isolation cages, we will grow, evaluate, self-pollinate, and make new selections from 60 separately trained winter squash plants from other populations. See previous section for descriptions of populations.

Screen cage design will likely involve using caterpillar tunnel-style hoops spaced at 10 feet and covered with insect exclusion netting. We have priced structures at approximately $1200 each. Hives of Bombus impatiens bumble bees will be used for pollination. Each hive costs approximately $200.

In 2023 at Care of the Earth Community Farm we will grow and do maternal selection from 100 separately-trained plants of the population derived from a cross between Waltham butternut and San Jose Mountain Club squash. We will plant 5 plants each of 10 hand-pollinated selections from 2022 of the already named and released Xiye butternut. It continues to need refining. We will do observation and selection for resistance to bacterial wilt, DM and black rot as well as productivity, vine length, fruit size and shape, flavor, and keeping quality. We will also plant 5 plants each of 10 selections from a gene pool with smaller fruit and compact vines.

In 2024 we will use the three screen cages for 3-5 squash seed production crops (we may be able to fit one pepo and one moschata in some cages if varieties we decide to produce are compact). Compared to the 2023 growouts these will involve less intensive evaluation of fruit quality but will still allow us to continue to confirm feasibility of squash seed production in screen cages, correcting any problems that may have come up in 2023. At least one of the cages will be used for summer squash seed production, and at least one will be used at Care of the Earth Community Farm.


Click linked name(s) to expand/collapse or show everyone's info
  • Megan Allen - Producer
  • Micaela Colley - Producer (Educator and Researcher)
  • Lalo Lazaro - Producer


Materials and methods:

See results and discussion

Research results and discussion:

Report on Year 1 (2023)

In 2023 we conducted summer squash variety trials and winter squash breeding trials at both Twin Oaks Seed Farm and Care of the Earth Community Farm. At Twin Oaks Seed Farm we also successfully piloted squash seed production in pollination isolation cages.

Summer Squash Trials

At Care of the Earth Farm the trials included a Cucurbita pepo species trial focused on downy mildew and plectosporium blight, which has become endemic in East Tennessee. The mid-July planting had very high plectosporium blight pressure, followed by high downy mildew pressure. All of the more common open-pollinated varieties in the trial were killed by plectosporium blight. The varieties that remained were all vining varie- ties originally from Mexico or Guatemala, many of which we got from the USDA germplasm bank. They all had intermediate to strong resis- tance to downy mildew. The most resistant to plectosporium blight was “PI449350”, followed by “PI442321” and then “Tatume” and “PI438700”. The drawbacks to both “PI449350” and “PI442321” is that they are later to produce and they are vigorously vining.

We also conducted Cucurbita moschata summer squash trials at both farms. Moschata species summer squash are notable for their immunity to plectosporium blight and vine borers. Almost all summer squash in the U.S. are pepo species, but we found moschata summer squash varieties originating from Korea, Brazil, France and Italy to include in the trials. None of the varieties were affected by vine borer at either farm (Twin Oaks tends to have heavy pressure and Care of the Earth much lighter pressure).

In the first succession at Twin Oaks (planted May 25th), the most productive varieties were Teot Bat Put (an oval-shaped variety from Korea) and Longue de Nice (from France), followed by Menina Brasileira Pre- coce (Brazil), Tromboncino (Italy), Jin Dong Ae (Korea) and Mini Paulista (Brazil). In the second succession (planted July 15th), Menina Brasileira Precoce was by far the most productive, likely due to its standout downy mildew resistance. The Korean moschata summer squash varieties are notable for their earliness and compact vines, as well as excellent flavor and likely good marketability in terms of recognizable summer squash shape. We plan to especially work with Jin Dong Ae and Teot Bat Put in the future, as they also had good yields. Note that many of the other varieties are fully vining squash plants that need 8-10 feet row spacing. Longue de Nice showed promise but had a tendency towards blossom end rot. We’ll see if we can select against that in the future.

At Care of the Earth, the trial was conducted under high downy mildew pressure, with a 6/28 planting date and rainy conditions that persisted until mid-August. “Tromboncino” was the best producer by count and by weight, although their shape and flavor are not ideal. We were also impressed by “Mini Paulista” (a variety from Brazil) and “Trombambino LOT 22-4901” (an unreleased variety from Michael Mazourek at Cornell University) as they were fairly productive, had some DM-resistance, and had better shape and 􏰀lavor than “Tromboncino”; they are both vining.

Squash Seed Production in Pollination Isolation Cages (Twin Oaks Seed Farm) As part of our squash-focused SARE grant, we used pollination isolation screen cages for the first time, with three separate winter squash seed production growouts. This allows us to save seed from several varieties growing in the same field without having to hand pollinate. (Hand pollination is very labor intensive and doesn’t work for some varieties.) We used a “meso tunnel” design that we learned about from “The Current Cucurbit” project out of Iowa State. Meso means mid height, as opposed to low or high tunnels - these are made out of 1⁄2 inch x 10 foot metal conduit bent with a hoop bender to create hoops that are about 3.5 feet tall. The hoops are arranged in two rows, and covered with a 20 foot wide “Protecnet” screen cover, to create cages 11 feet wide by 50 feet long, suitable for 15-20 fully vining squash plants. bought small bumble bee hives from a Michigan-based company called Plant Products Inc, which were successful in pollinating the squash in the cages. We got good harvests from all the cages! Seedstocks produced were “Choctaw Sweet Potato,” and two different selections of Cuban Neck Pumpkin made at Twin Oaks Seed Farm in 2015 and 2019. We’re excited to have this tool available for future seed production and plant breeding projects – it means we’ll be able to grow many more varieties in any given year. The meso tunnel design was cheaper than the caterpillar tunnels we had envisioned when we submitted our project proposal. For this reason we have extra funds earmarked for tunnels that we plan to use to create several additional tunnels in 2024, for use at both Twin Oaks Seed Farm and Care of the Earth Community Farm.

Winter Squash Breeding Trials at Twin Oaks Seed Farm

South Anna x (South Anna x Chinese Tropical Pumpkin): We grew approximately 120 plants, allowing them to intertwine but tracing the fruits back to the vines for most of them. In this project we’re especially emphasizing keeping quality, in addition to eating quality and productivity. We were happy with the characteristics of the plants in the plot as a whole, but also selected five stand-outs for 2024 stock seed, and started selling sample seeds from these plants under the name Bakers Branch Butternut. Two additional selections with smaller fruits we plan to keep working with to create a small-fruited version.  This growout was isolated from other moschata species squash, so no hand pollination or isolation cages were employed.

South Anna: We traced back fruits to over 120 plants, placing the fruits at the base of each plant. The best 40 plants (in terms of yield and appearance) were weighed and further evaluated for keeping quality and eating quality. We are especially aiming to improve keeping quality and yields of the variety. This growout was isolated from other moschata species squash, so no hand pollination or isolation cages were employed.

South Anna x (South Anna x Guatemalan Green Ayote): We grew 22 plants from three 2022 selections of this population. Each plant was separately trained and self-pollinated, and then evaluated for yield, foliage resistance to downy mildew, keeping quality and eating quality. What we’re going for with this population is a dual purpose squash that has tender seeds for roasting as well as excellent dessert eating quality – plus downy mildew resistance, good yields and good keeping quality. Four plants stood out for all these categories and we are growing them in 2024.

Moranga Coroa x Winter Sweet: This is a maxima species breeding project, and the main goal is development of vine borer resistant plants. Note that moschata species varieties, which we mostly work with, are naturally vine borer resistant, but that maximas generally are not. We grew 54 plants from seven 2022 selections. The overall rate of vine borer resistance was 39%. One of the selections had 68% vine borer resistant plants. We did eating and keeping quality evaluation on fruits from the best vine borer resistant plants and are growing plants from four of the selections in 2024.

Guatemalan Green Ayote:

Chinese Tropical Pumpkin: We grew 11 plants, self pollinating and evaluating each one separately for productivity, eating and keeping quality, as well as fruit shape. We plan to move forward with four of the selections.

We also trialed some new varieties from Brazil, including Pataca Gigante, Moranga Exposiciao, Mini Abobora Aura Rosa, a new seedstock of  Moranga Coroa, Majestade, and Goaninha.

Moranga Exposiciao (a C. maxima variety) stood out for its vine borer resistance (4/4 plants were resistant). It has a beautiful deep orange color but bland flavor. The new Moranga Coroa seedstock however (from ISLA Seeds, also a maxima) showed only 2/4 plants resistant. We still have Moranga Coroa seedstock derived from seeds we got from KCB Samen in 2018. These showed better resistance (4/4) but unfortunately our population went through a 1-plant genetic bottleneck that has negatively affected fruit size and productivity. Goaninha (a C. moschata squash) had very good flavor, brix and dry matter, as well as good downy mildew resistance.

Continued Improvement of Xiye Butternut and Ofelia Butternut at Care of the Earth Farm
In 2023, we evaluated 20 individual plants in each of 8 different Xiye Butternut gene pools, evaluated 100 individual plants of our main breeding line, and did seed growouts. In the Xiye gene pool comparison, we kept data on vine length, downy mildew resistance, fruit type, consistency of fruit type, and productivity, flavor and storability. Our intention with these growouts is to better understand the connections between plant and fruit phenotypes and storage and flavor profile. In the larger evaluation, we kept data on vine length, downy mildew resistance, fruit type, consistency of fruit type, and productivity in order to inform self and cross pollinations and for ongoing selection work. Although we continue to select for a more uniform squash, we also want to maintain several more diverse gene pools for climate resiliency and for future breeding. We were again very impressed with Xiye’s DM-resistance and productivity even in a challenging season.

We also evaluated 180 individual plants of Ofelia (a smaller sister variety of Xiye) for vine length, downy mildew resistance, fruit type, consistency of fruit type, and productivity. We were surprised by the uniformity of the plants across evaluation criteria. They were quite productive and showed good DM-resistance. We also really liked their size, right under 3#. We made several self-pollinations and cross-pollinations and hope to improve neck thickness, depth of flavor, and keeping quality in 2024.

In 2024 –

We are continuing to pilot squash seed production in meso-tunnel insect isolation cages with introduced bumble bees, with five cages at Twin Oaks and 3-4 cages at Care of the Earth Community Farm. These growouts will be producing and continuing selection of varieties that we selected in 2023.

We are conducting summer squash breeding trials at Twin Oaks with F2 seed from several Korean summer squash hybrid varieties, including Teot Bat Put and Jin Dong Ae. We will continue to select Longue De Nice against blossom end rot, and will advance F1 crosses between Jin Dong Ae and Mini Paulista, and between Teot Bat Put and Mini Paulista.

At Care of the Earth Community Farm we are continuing to evaluate C. pepo squashes for plectosporium blight resistance and to advance the selection work with Xiye Butternut and Ofelia Butternut.



Participation Summary
5 Farmers participating in research

Educational & Outreach Activities

2 Published press articles, newsletters
1 Workshop field days
10 Other educational activities: Instagram posts about the project (nine posts); a podcast episode for "Voices from the Field" (produced by SARE and ATTRA)

Participation Summary:

15 Farmers participated
Education/outreach description:

Update 6/23/2024: Our outreach to date has consisted of instagram posts about the project (nine posts), a report on the project in our 2024 print catalog (, an interview with Farm Show magazine, a podcast episode for "Voices from the Field" (produced by ATTRA and SARE), and a farm/project tour at Twin Oaks Seed Farm in August of 2023. We are planning project field days this year at both Twin Oaks Seed Farm and Care of the Earth Community Farm.


Our outreach plan includes field days, promotion and discussion of the project on our website and in email newsletters, short posts to instagram, short videos, and presentations at conferences.

We are planning five field days - one each year at each farm (Care of the Earth Community Farm and Twin Oaks Seed Farm), with an additional field day at Twin Oaks Seed Farm in 2023 to be able to reach more people. Outreach will especially focus on farmers in our respective areas, and will primarily be through direct invitations. We will also promote them through Virginia Association for Biological Farming (VABF), and through Care of the Earth Community Farm's CSA network. We have found field days to be an excellent way to engage other farmers with our work, and our field days have been well attended.

We will be making short picture posts to instagram about the project on a regular basis throughout each growing season. In addition we will be recording short videos from the field to post on youtube and on our website. Updates on the project and the final report will be available on our website research page.

We will apply to do presentations about the project at several conferences, including CFSA Sustainable Agriculture Conference, VABF's winter conference, and at the 2024 Organic Seed Alliance conference.

Our 2020-2021 butternut squash grant recieved good publicity through field days, a webinar organized by Culinary Breeding Network, and an article written by Candace Pollock that appeared on the SSARE website and in the ACRES USA publication.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.