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  • Penn Parmenter


By Penn Parmenter:

A Grex is a mixture of varieties growing together and encouraged to cross-pollinate. The seeds from those crosses are grown out again and again. Instead of crossing two parents to create offspring, the breeder crosses dozens. The word Grex means ‘flock’.

Joseph Lofthouse’s Medium Maxima Landrace Squash Grex. (Grown here at 8,000’.) Lofthouse is famous for ‘promiscuously pollinated’ varieties that adapt well to his climate. The grex as a whole is like a litter of kittens; there's a strong family resemblance but each plant produces unique fruits. PHOTO: Penn Parmenter

The first year of a Grex grow-out is naturally culled by the climate, in our case, a short season with hot days and cold nights. Next, the survivors of that first year are grown out again and encouraged to cross. The third year is when the magic really happens; explosions of colors, shapes, textures, and flavors burst forth.

The breeder then begins to select the best from this big pile of genetic diversity. Traits we are looking for here in Colorado, especially at altitude, are earliness, climate resilience, and, of course, flavor.

Other examples of desirable traits could be a more tender skin on a winter squash or a bright yellow color with a pronounced crooked neck on a summer squash.

The good news is, the Grex Breeder has already done this preliminary work for us and once we get our hands on those seeds, we can continue where he or she left off.

I called my friend Joseph Lofthouse, a Grex and Landrace Breeder to ask him a few questions. He lives in northern Utah and he is not concerned with maintaining stabilized lines or creating the next new thing. Instead, he is famous for ‘promiscuously pollinated’ varieties that adapt well to his climate. Because of where he lives, Joseph needs to select for earliness, which Nature does itself since only the fastest maturing fruits make it before a killing frost, usually the first week of September. He also is committed to FLAVOR and only selects the seed from the best tasting fruits. Yet the incredible background of genetic diversity continues to express itself in a glorious display.

The term Landrace means the seed has adapted to the region. This can be done in your garden or in many gardens as the collective grow-out and feedback of a particular variety in a particular region tells the whole story. A variety can be a Grex and a Landrace, and in Joseph’s case, both.

When you find a Grex or Landrace variety you can pick up where the breeder left off. You do not need to be a breeder to grow or continue a Grex. Let’s say you purchase Joseph’s Medium Maxima Winter Squash Grex. You will observe a beautiful array of colors, shapes, textures and flavors, all crossed within that same family of squashes, in this case, Cucurbita maxima.

Seeds in a Grex need to be compatible. For instance, there are four families of Squash so in the Maxima Grex, Joseph crossed many Cucurbita maxima squash varieties; the other three families will not cross with them.

Joseph has already selected this ongoing mixture for earliness and flavor so now you can begin to select for your own preferences. Each year as you discover squash you love, that stand up well to nature or mature first, you can save seed from them again, and select those out, or remix them with earlier grown seed, and see what happens next. You will continually be saving the seed from the best and earliest while still allowing the genetic diversity to play out.

Adaptation happens faster in a Grex grow-out than a stabilized variety because it has more possibility for genetic recombination. More combinations can be tried by nature, giving you endless possibilities for something that is just right for your climate. If you notice undesirable traits like lack of vigor in the plant, just cull those out.

Adaptation is also faster with out-crossing varieties like corn or squash, and they work best for a beginning Grex grower. Hand-pollination can be done but in this case, wind and insects will do the job for you.

Another way to play with a Grex is to buy a ready-made mix of something from a seed catalog, (Pinetree offers lovely mixes), grow them together, let them cross, save seed, repeat…

I encourage you to try growing a Grex! it’s easy, fun, and as you go, you will be selecting for your climate conditions, giving you more resilient seed for your future gardens.

Penn & Cord Parmenter garden and grow food and seed near Westcliffe. Both are regional high-altitude gardening instructors and the founders of Smart Greenhouses LLC and Miss Penn’s Mountain Seeds. Visit



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