Hemp: What we’ve learned about getting the most from your seed

Planning to plant hemp

If you read my previous posts about the emerging hemp industry after the passage of the 2018 Farm Bill, you know I’ve been thinking a lot about how to break into this new crop market as an existing vegetable farm. Lately, my thoughts have been centered on how to start planting.

“Root-to-Shoot” for hemp

Whatever we grow at Spinaca, my MO is to use the whole plant for multiple applications per our Root-to-Shoot philosophy. Hemp is slightly different, though. With hemp, seeds are bred for their end result, meaning some seeds support fiber production while another might support oil production. Yes, some seeds are hybrids, but they produce mediocre yields of both fiber and oil, so we’ll separate plantings to maximize yields independently. That being said, we’ll still be able to utilize every part of what each plant grows.

Matching hemp farming with daylight hours

One thing I’ve learned while researching seeds is that hemp is a short-day crop. This means the flowers will only develop when daylight hours are less than 12 hours per day, which is similar to a lot of flowering vegetable plants. (Onions, for example, are designed to grow as short-day, long-day, or intermediate-day varieties.)

So, depending on what hemisphere you’re in, if it’s a climate suitable for growing, you have to pick the best variety based on a plant’s tolerance for sunlight. If you put a short-day crop in a long-day growing season, it will bolt to seed and you won’t be able to get a crop off of it, which is the opposite of what it’s supposed to do. So you have to match the right variety to the correct amount of daylight hours, which are typically labeled short-day, intermediate-day, or long-day.

Credit Better Wyoming

Picking the right time to plant

Planting hemp in August is a good bet for those of us on the West Coast when daylight lasts roughly 13.5 hours. The thing to remember, though, is that those daylight hours are on a downward slope. We lose a minute each day moving into September and October. That means I’ll have a crop that’s triggered properly to produce flowers and then seeds to refine the oil from. If I were to plant in, say, January, daylight hours would start short but grow longer, resulting in a plant that grows too quickly to be triggered to produce a flower.

Hemp farming and crop rotation

Of course, any working farmer will tell you it’s more complicated than picking the right seed and planting it at the best possible time. For someone like me who grows vegetables, crop rotation has to be taken into consideration, too.

If I have ground available for a rotation, I have to look at how that rotates with my other cash crops. I can’t claim 100 acres of land to grow hemp during the critical vegetable-growing months of spring. If I’m going to rotate hemp it has to be “after the turn,” or at the back end of the planting cycle, in fall.

Considering the roles of male and female hemp varieties

Hemp plants can be either male or female, but female plants produce higher yields of oilseed and fiber content. This is primarily because male plants die off at an earlier stage and never really hit full production. As seed breeders are creating and developing varieties, they’re finding that it’s best to keep female seeds for commercial production of hemp, and male seeds for pollination to create the next seed crop. On my end of that equation, I only want female seeds; a seed developer, however, would want both.

And on that note, I’ve also learned that seeds need different spacing depending on their end application. For instance, for producing oil, we will want to plant less seed per acre than we will for textile production. Using less seed means the plants have more room to breathe, which allows for more flowers on the plant to set, set again, and set again.


If you’re interested in learning more about industrial hemp production, the following are a couple of resources I’m finding helpful right now:

  • The Purdue University Hemp Project shares a lot of broad information on hemp and hemp seed production
  • The University of Kentucky has a progressive Hemp Program, including an upcoming hemp research field day in August and a downloadable enterprise budget for calculating and optimizing hemp production efforts. Use this sheet to manipulate data based on your particular needs and conditions: a very helpful find.

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