Growing out the collection: Preservation methods to maintain varietal purity

Preservation explains their work in the field and the need for isolation distances

 Hannah harvests beans inside an isolation cage

Hannah harvests beans inside an isolation cage

Heritage Farm is a plant genebank - we maintain thousands of varieties of plant types. We call our seed bank, orchards, in vitro tissue cultures, and vegetative plant repository the collection and every year we grow out a portion of the collection to increase and/or refresh stock and for evaluation and observation purposes.

Collection Needs

Each year, field manager Bryan Stuart determines the production capacity of our gardens while the Collection curator, Tor Janson, chooses the actual varieties that will be grown out.

This year approximately 1000 varieties of 65 different species were grown: about 500 varieties were grown for seed regeneration and 500 for evaluation and observation. Evaluation and observation is important; it allows us to determine if our stored seeds are viable and growing true to type.

Isolation Distances

One of the most difficult parts of planning each year’s grow out is making room for the tomatoes and beans; together these two species make up almost 40% of the collection. The difficulty lies in the fact that they are mostly inbreeding plants: if different varieties of tomatoes or beans are planted close together, they can cross-pollinate and the fruit will lose some traits, while gaining others.

According to field manager Bryan Stuart, “...as a genebank we strive for absolute purity for each variety, so we isolate these plant varieties by 100 feet in the open field.”

 A field with plots planted at isolation distances on Heritage Farm

A field with plots planted at isolation distances on Heritage Farm

Tomatoes and beans are planted in “isolation gardens,” plots that allocate a spot every one hundred feet for a single tomato or bean variety. Between these plots, other species such as peppers, okra, and cabbage fill the gaps. In a 60 x 350 foot garden, seed can safely be produced from 4 tomatoes, 4 common beans, and numerous other species planted in between. All in all, a garden this size may accommodate over 40 individual varieties.

90% of our collection grow outs are done in these isolation gardens using distance isolation to maintain varietal purity, while about 10% of our crops are grown in isolation cages.

 Bean pods after harvest

Bean pods after harvest

Isolation Cages

Isolation cages increase our capacity to grow more than would be safely feasible in the open field using distance isolation. Watermelon, for example,  requires a great deal of space between varieties to prevent cross-pollination, about ½ mile.

Other varieties, like carrot and parsnip are also routinely grown in isolation cages due to the abundance of their wild relatives with which they can cross pollinate. Occasionally, when cages are available and a working isolation garden is not, tomatoes and beans will be grown in isolation cages as well.

Field Crew

 Em

Em

I decided to take advantage of the beautiful Fall weather and  jumped in the truck with the Preservation garden crew leader, Korbin Paul. Korbin took me out to the area that is referred to as South Farm where the preservation crew was busy harvesting tomatoes and beans from isolation cages.

 Steven

Steven

Three workers were harvesting inside a 12x22 foot isolation cage that day, Korbin, Hannah Oakley, and Em Rocksvold. Hannah showed me that the variety of beans they were harvesting that day are ready when their pods feel like paper.

The crew works steadily down the rows of beans, singing songs that they make up about vegetables and gardening and each other.

Meanwhile, Steven Burg and Kevin Storey are taking down the isolation cages that have already been picked clean. Both of them enjoy working outside and being in the fields and woods. “Being out here makes work seem like play work. We don’t look at the clock all day, we just get after it,” says Kevin.

After the Harvest

All the varieties collected today will be brought into various sheds and logged as harvested. The crops will get cleaned and dried, then packaged and ultimately stored or distributed.


Seed Savers Exchange is a non-profit organization located in Decorah, Iowa, with a mission to conserve and promote America's culturally diverse but endangered garden and food crop heritage for future generations by collecting, growing, and sharing heirloom seeds and plants.