Greens are no longer just green and they are not just lettuce. No matter where you live, the best arugula, Swiss chard, or baby beet greens haven’t traveled far; they were probably picked this morning and delivered to your local market within hours. But the seed that grew them was likely grown in Oregon. Oregon’s diverse climate makes it one of the best places on earth to grow seeds. Fertile soils and mild winters encourage plants to grow and flower; long dry summers ripen and dry the seed. Combine that with care taken to control cross-pollination, and Oregon seeds have earned a reputation as among the purest and best in the world. Almost half of the world’s carrot seed is grown in central Oregon. Sweet corn, bean, and pea seeds are grown in the drier parts of the Columbia and Snake basins; seed for cool-weather crops such as spinach, cabbage, and chard are grown in the Willamette Valley.
Oregon’s specialty seed growers work together to maintain that reputation for purity. They protect their seed crops by mapping isolation zones around fields where specialty seeds are grown. Growers use pushpins to mark locations of their seed crops on large maps located at OSU Extension county offices. These so-called pinning maps help growers maintain enough distance between seed crops to ensure that wind-blown or bee-carried pollen from one crop does not mix with a different crop.
An ongoing concern of many specialty seed growers is contamination by pollen from closely related plants. So far the voluntary pinning maps have prevented damaging cross-pollination. Debate continues in the Valley over the introduction of canola and the possibility of its cross-pollinating with closely related turnips, cabbage, and broccoli, or sharing pests and diseases.
The issue of cross-pollination becomes more complicated when closely related plants have been genetically modified, increasing the chance that engineered traits could show up unintentionally in traditional seed crops. Genetic contamination in organic seed crops is a particular concern because the national organic certification standards prohibit the use of genetically modified organisms, including seed.
Ordinarily, isolation among seed fields prevents cross-pollination. Crop isolation also maintains the genetic purity of desirable traits that characterize many new vegetable varieties, like the nutrient-rich red lettuce and purple tomatoes in your salad. All of the vegetable breeding at OSU is done through traditional methods, a process that takes years of selection and careful record keeping. Traditional plant breeding crosses plants with desired characteristics and selects the best of each generation. Those offspring that don’t measure up because, say, they are off-color, prone to disease, or they just taste bad, are removed as rogues before they have a chance to flower and produce pollen.
Careful breeding and protection from pollen movement ensures that the seed in the ground—and the greens in your salad—contain no hidden surprises.