Understanding the Seed Catalog

January 10, 2022

Marion Barnes – Senior Clemson County Extension Agent

It’s January, and the seed catalogs are arriving faster than the bills from Christmas shopping. As we feel the effects of winter, all those colorful photos and mouthwatering descriptions of vegetables make the average gardener want to start ordering seed for the spring. Before you tackle that pile of newly arrived catalogs, go out and take a look at your garden and make notes on how much room you have and where you want to plant. Hopefully, you remember which varieties worked well last season. Also, make a list of new varieties you might like to try. One of the first questions you need to ask is, “Do I need to order from a seed catalog?”. If you are not too picky, you can probably find most if not all your needs at the local feed, seed, and garden supply store. As you look through your seed catalog, you may run across terms or words that are unfamiliar. Let’s go over a few that are often found in most seed catalogs.

  • Cultivar: The word cultivar comes from the term “cultivated variety” and is a variety with specific characteristics or traits. A seed-grown cultivar can be either a hybrid or an open-pollinated variety.
  • Hybrid or F-1 hybrid: An “F-1” or first-generation hybrid occurs when plant breeders select two pure lines of plants that produce identical offspring when self-pollinated and cross-pollinated. These lines  (parent plants) produce seed with desirable traits from both parents. Some common traits that breeders try to enhance are disease resistance, earliness, increased nutrition, and color or appearance. Due to production methods, hybrid seed are usually more expensive to produce. Seed saved from F-1 hybrids will produce plants that will not “come true”; in other words, they will lack the desirable characteristics or traits of the parents, which were specifically crossed to incorporate them.
  • Open-pollinated or (OP): These varieties are seeds that result from pollination by wind, insects, self-pollination (where both male and female flowers occur on the same plant) or other natural means of pollination. Seed saved from open-pollinated varieties will “come true” or produce plants with traits like the parent plant from which the seeds were harvested. Remember that wind and insects will pollinate different (OP) varieties planted in close proximity. For example, field corn can pollinate a stand of sweet corn if planted nearby. Cross-pollination may not be much of an issue if you do not plan to save the seeds or unless you mind a few yellow grains of corn in your white sweet corn varieties!
  • Heirloom: Heirlooms are open-pollinated varieties that have resulted from natural selection rather than by a controlled hybridization process used by plant breeders. Like open-pollinated varieties, seed saved  heirlooms will “produce true.” Most heirloom varieties originated in the 1940s and 1950s before plant breeders began producing and selling modern hybrid seed. Seed saving organizations have played a key role in preserving many noncommercial heirloom varieties.
  • Heritage: Varieties that have received special recognition for having stood the test of time across generations because of traits such as reliability, outstanding flavor, and wide adaptability. They may be open-pollinated as well as hybrid varieties.
  • Organic: The words “Certified Organic” on a seed packet means that the seed meets all the detailed rules and regulations specified by the USDA’s National Organic Program. In the United States, organic regulations specify that land on which the crops are grown cannot have prohibited substances applied for three years before harvest. The operation must be managed according to an Organic System Plan approved and regularly inspected by a USDA accredited certifier. Organic seeds are grown without the use of synthetic fertilizers and pesticides.
  • Hardiness zone: The United States is divided into hardiness zones based upon the lowest average winter temperature for the area. The USDA developed hardiness zone maps to aid gardeners and landscapers in selecting plants that survive the winter.
  • Determinate and indeterminate: These terms are often associated with tomatoes and how large the plants will grow. Determinate plants tend to stay more compact, bushier and reach a certain height and stop growing. When flowers blossom at the tip of the branches, plants have reached full size. They do well in cages and are suitable for gardens with limited space. The indeterminate types tend to grow tall, get Viney, and grow all summer. They usually require considerable effort to stake and support, keeping them off the ground and growing upright. Indeterminate tomato plants usually produce all season until disease or a hard frost hits. Packaging may say IND,  INDT, or Indeterminate.
  • Days to maturity or harvest: Usually measured in days and refers to the average number of days it takes after you plant seed or set transplants before your first expected harvest. This indicator can be highly variable and is affected by weather, temperature, and growing conditions.
  • Disease tolerance and disease resistance are good traits, but the terms have different meanings. Tolerance is a plant’s ability to reduce the effect of infection and grow and produce an acceptable yield despite an attack by disease-causing pathogens. Resistance is an inherited trait or characteristic that the plant has to prevent or significantly reduce infection by disease-causing pathogens. You may notice acronyms referring to disease resistance in seed catalogs. These symbols or letters indicate which diseases a plant is resistant to. Some of the more common ones to watch for when selecting tomatoes, for instance, are TSWV (tomato spotted wilt virus), V ( verticillium wilt), RKN (root-knot nematode), and F (fusarium wilt).
  • New and improved: These words are not just selling points; they often mean the variety has been changed in some traits, often substantially.

Most seed companies have websites where you can request their catalog or shop online. Seed catalogs are an excellent way to keep up with new varieties, and they usually have a greater selection than many local seed and garden centers.

For more information on gardening contact your local Clemson Extension office.

Clemson University Cooperative Extension Service offers its programs to people of all ages, regardless of race, color, gender, religion, national origin, disability, political beliefs, sexual orientation, gender identity, marital or family status and is an equal opportunity employer.


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