In my last post, I began to provide some detail about some basic tomato terminology. Understanding the basics leads to more successful gardens – and happier gardeners. With so many tomato choices, confusion can easily set in. Since just about all gardens contain tomatoes, and most gardeners crave them, a successful harvest every year is a really important goal. Part of that success can be achieved by selecting the right varieties for our climate, soil, and garden type – this contributes to a good start.
Now that we’ve discussed growth habit in my last post – indeterminate, determinate and dwarf tomato varieties – the next place to go is clarifying the three terms that describe the genetics of the varieties at the highest level. Understanding what the terms hybrid, heirloom and open-pollinated mean help to set not only expectations and possibilities, but define the “type” of tomato garden – such as high production, living history, and rainbow of colors and flavors.
Open-Pollinated
A tomato variety that is genetically stable – one that can be grown reproducibly from saved seed – is called an open-pollinated variety. The genetic stability of such a variety allows it to be passed on and be in existence for decades or centuries (unless it becomes cross pollinated along the way, but that’s another story).
Heirloom or Heritage
A special type of open-pollinated variety has old bones; it has stood the test of time. This type of variety is known as an heirloom, or heritage, type. Determining the particular age that defines an heirloom is arbitrary and ever-changing, and there is likely lively disagreement among heirloom tomato enthusiasts. I like to use the date of 1950 as an easy to remember guideline, and I will tell you why I chose that date below. Heirlooms can be either family heirlooms, handed down from generation to generation, or old commercial varieties that managed to survive to this day.
Most heirloom and open pollinated varieties are indeterminate in growth habit. The gene for “self- topping” (determinate growth) didn’t appear until the 1920s. Though the dwarf growth habit has been known in the U.S. since the 1850s, dwarf growing varieties continue to be quite rare.
The open-pollinated/heirloom designation can be very confusing. I like to think of it as thus: All heirlooms are open-pollinated, but only open-pollinated tomatoes that pre-date 1950 are heirlooms.
Hybrid or F1 Hybrid
In 1949, the Burpee Seed Company released a tomato variety that shifted the paradigm of how companies worked toward new releases. The ground-breaking variety, Big Boy, was the very first well-known, extremely popular variety sold as hybrid seed. Burpee horticulturists took pollen from one tomato parent and placed it on the style of another parent. The fruit that developed contained the hybrid seed, often designated as F1, meaning first filial generation; those seeds are what ended up in the packets of Big Boy mailed out to their customers or purchased on seed racks.
Seed companies shifted into creating and selling hybrid varieties from that point on for a variety of reasons; hence my use of 1950 as a key date for calling open-pollinated varieties heirlooms. Breeders prior to then carried out crosses – creating hybrids – but instead of selling the hybrid seed, they used it as a starting point for creating stable new open pollinated varieties. It takes up to ten generations to reach a stable, open pollinated variety.
Many newer hybrids are determinate or semi-determinate (taller than determinates, less out-of-control than indeterminate growth habit).
What it All Means
Just like heirloom and open pollinated types of varieties, hybrids are neither inherently good nor bad. Crossing varieties allows for the introduction of genes that lead to an ability of the variety to succeed in the presence of particular diseases (this is called either disease tolerance, or disease resistance). The letters after hybrid tomato names tell the tale; an “F” means tolerance or resistance to Fusarium wilt. “V” stands for Verticillium wilt, and so on. The presence of that letter doesn’t mean the plant won’t come down with the disease eventually, especially when the disease population is very high.
On the other hand, the lack of a letter doesn’t mean that a variety is doomed to fail. Few heirloom or open pollinated tomatoes have been rigorously assessed for their ability to handle all of the various tomato diseases. Trial and error is the key to eventual success, as well as finding out from the local extension agent which varieties do well in your particular area.
Seeds can be saved from hybrid varieties, and the resulting seedlings will grow tomatoes. However, the results may be similar to, or very different from, the hybrid itself, depending upon the genetic differences of the parents. Often, growing out seed saved from a hybrid is a way to create a new tomato variety; this is actually the basis for our Dwarf Tomato Breeding project, in which we are making crosses and working for years to end up with a stable, pleasing new open pollinated variety.
One last word on tomato designation. The term “heirloom” has taken its lumps recently. I think there are two reasons for this; overuse, and lack of standard, consistent use. I love the term, because it means that it is a variety that was sufficiently cherished that it can still be grown today. What I don’t love is when restaurants offer “heirloom tomato samplers”, then load them up with hybrids and more recent open pollinated varieties.
There can always be so much more to say on any tomato-related topic. However, I will stop here and let everyone digest what I’ve provided….and please, post comments, ask questions, and share your favorites!
A few varieties in each category that I enjoy:
Hybrid: Sun Gold, Big Beef, Lemon Boy, Whopper, Better Boy
Open-pollinated: Black Cherry, Lucky Cross, Cherokee Chocolate, Dwarf Sweet Sue, Speckled Roman
Heirloom: Lillian’s Yellow Heirloom, Ferris Wheel, Brandywine, Andrew Rahart’s Jumbo Red, Hugh’s
Craig Lehoullier is an heirloom tomato expert (and amateur plant breeder). He currently is on book promotion tour for Epic Tomatoes, setting upcoming tomato workshop events, updating his website and blog, devising a totally new, all-heirloom weekly podcast, shooting a tomato know-how video series and pondering topics for future books. He is co-leading the Dwarf Tomato breeding project to put 36 new dwarf-growing, open-pollinated tomatoes in the hands of various small seed companies. Read all of his MOTHER EARTH NEWS postshere.
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