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What Variety of Hemp Should I grow?

What Variety of Hemp Should I Grow?

One of the first things a potential hemp grower must decide is what type of hemp to grow. There are three main types of hemp production: Grain/seed, fiber, and CBD. Each uses different seed varieties, equipment and techniques, and end markets, and requires different amounts of land, labor, equipment, nutrients, and weed and pest control. Very briefly, this is what you need to know about each type of hemp crop.

General Morphology of Feild Hemp

 Hemp is a dicotyledonous plant (having two cotyledon leaves) and has both monecious (male/female flowers on the same plant) and dioecious (separate male plants and female plants) plants)

  • Hemp is naturally a dioecious variety and most agronomic varieties are as well.
  • The ratio of male to female plants is typically 1:1 

Hemp is a cross-pollinated, wind-pollinated plant. Only male plants produce pollen (dioecious plants). The flowers on the male inflorescence open from the bottom of the plant first then to the top of the plant. Once the male plants have fully shed their pollen they will senesce and die. 

  • Pollination typically lasts 2-3 weeks depending on weather conditions and uniformity of the stand.
  • It is said hemp can produce more pollen than all other cultivated crops. The pollen from hemp can travel up to 10 miles. 

Female Hemp Head

Female Hemp Head

While both male and female flowers can be identified at the nodes of the plant, female flowers can be differentiated by the enlargement of a symmetrical tubular pistillate calyx (floral sheath) and the protruding white stigma. The male staminate calyx has a curved claw shape that will then develop into round pointed pollen sacs that have five radial segments. Males will not have the white stigma like those found on female flowers.

  • Male plants are the first to show signs of flowering with the staminate visible at the nodes of the plant.
  • Flowering typically begins 4-6 weeks after planting.
  • Female plants can usually be identified 5-14 days after the males. 

Female Hemp plant with arrows pointing to stigma

Female Hemp plant with arrows pointing to stigma

 Hemp is photoperiod-dependent and is considered a “short-day” plant. 

  • The vegetative phase turns to reproductive phases only when the daily exposure to sunlight is shorter than a specific maximum duration (critical day length) 
  • 14 hours or less of daylight will typically trigger flowering.
    • Shorter day length can accelerate the onset of flowering 

    The root system of hemp typically reaches depths of 1-2 feet in the soil. 

  • Wet soils will keep root systems shallow while drier soils encourage deeper rooting.
  • Sandy and loamy soils generally allow for larger root formation
  • Female plants have much larger and stronger root masses than male plants. 

Stalk height and thickness is significantly affected by soil type, fertility and physical/chemical characteristics of the soil.

  • Stalk length is influenced more by nitrogen while stalk thickness is influenced more by plant density and row spacing. 
  • Light (sandy) to medium (loamy) textured soils tend to grow much taller plants than heavy (clay) soils due to better drainage and less compaction. 
  • Seed/grain varieties typically stand 4-6 feet tall at harvest.
  • Fiber varieties can reach heights of 8-14 feet by harvest. 

Hemp grown for seed grows much slower, initially, than hemp grown for fiber. However, near the end of the vegetation stage, seed hemp grows much more rapidly. 

  • Weed suppression is less effective with grain varieties than with fiber varieties.
  • Hemp can grow 1-2 inches per day during its rapid growth stage which typically begins 4-6 weeks after planting. 

Hemp Roots

Hemp Roots

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Hemp for CBD

These cultivars are very bushy, and may reach heights of 6 to 12 feet. These plants are grown and harvested for cannabidiol (CBD) which has many potential health applications. Note: Legacy Hemp does not work directly with farmers growing for CBD at this time. Legacy Hemp sells and deals with primarily with grain and 

  • Planting time: Clones or other starters may be transplanted outdoors by mid-June. Greenhouse-only systems may plant year-round.
  • Planting method: By hand or by transplanter when using clones or starts.
  • Planting rate:  800-1,500 plants/acre, spaced 4-6 feet apart. 
  • Harvest time: Female plants grown to near maturity, mid-September to mid-October in fields; greenhouse harvests vary. 
  • Harvest method:  Plants are cut by hand and removed from the field.
  • Post-harvest handling: Dried in drying sheds or warehouse to processor’s specifications. After drying, flowers and some leaf materials are removed from stalks, packaged and sent to processor for oil extraction.
  • Other comments:  Only the female plants are used; male plants are terminated once identified

Grain hemp seed field

Hemp for Grain/Seed

These cultivars are slender, and about 5-7 feet tall. They produce  hemp grain, an oil seed with high protein content with high nutritional value. 

  • Planting time: Mid-May to mid-June
  • Planting method: Grain drill, broadcast seeder or corn planter
  • Planting rate:  25-35 pounds/acre
  • Harvest time: At maturity, generally 100-120 days after planting; mid September to mid-October
  • Harvest method:  Regular combine 
  • Post-harvest handling: Clean before storage in a grain bin, where forced air dries the crop
  • Other comments:  Some cultivars may also be harvested for fiber after combining

fiber hemp field tall

Hemp for Fiber

These cultivars are very slender, and range from 10 to 18 feet tall. These varieties are grown and harvested for bast fiber and hurd with great potential to be used in the fabric, construction, and various manufacturing operations. 

  • Planting time: Early May to early June
  • Planting method: Grain drill or broadcast seeder
  • Planting rate:  50-70 pounds/acre
  • Harvest time: Around the time of pollination, generally 45-70 days after planting; mid-July to early August
  • Harvest method:  Mower (sickle or disc mower) and a hay baler (round or large square)
  • Post-harvest handling: Left to field dry to 15% moisture, then baled
  • Other comments:  Some cultivars may also be harvested for seed, but special harvesting equipment may be necessary

Download

Legacy Hemp and the Wisconsin Department of Agriculture, Trade, and Consumer Protection have been working together to develop this information. Legacy Hemp is not currently working working with CBD cultivars, but this may be subject to change. We also have our seed brochure listed below. For your convenience, you can download this information here: