• Darby Hemp

Hemp Fiber: 10 Lessons on True-Fiber Cannabis Farming

Learn some of the basics of growing true-fiber hemp here in America, which many have ALWAYS believed would be the biggest cannabis industry of all, far surpassing recreational, medicinal and CBD-focused cannabis industries combined.


American recreational and medicinal cannabis industries are pretty big, without doubt, worth billions they are.

In gallops newly-classified hemp CBD between 2014 and 2019, and why, they’re calling it a 21st century Wild West-style craze for struggling farmers and consumers to reach tens of billions inside a handful of years. We’re likely to see operations springing up for other cannabis non-intoxicants like CBG and CBN before too long, adding to the cannabinoid rush.

But here’s the deal, and there’s one hell of an argument to be made to back it...American hemp fiber crops are a FAR BIGGER market emerging with FAR GREATER economic and environmental opportunities.

Hemp fiber’s a largely untapped, socially-accepted, easily renewable resource for lignin (in a time of unbelievable emphasis put on sustainable human systems), cellulose, and fiber we can transform textile industries with. Not to mention fibers for construction materials like hempcrete, biofuel applications, even carbon fibers used in supercapacitors or hemp batteries.

  • What? If you’re interested, feel free to bookmark our article, “Scientists on the Cusp of Disrupting How We Relate to Energy” concerning Hemp Batteries.

All eyes might SEEM like they’re on CBD, and hemp farming for CBD is going to be a great way to go for many for at least the next couple decades, but American hemp fiber is the big ticket non-therapeutic or medicinal agricultural crop cannabis has to offer alongside grain!

What interested farmers and ambitious entrepreneurs need right now is good information. Consumers crave a better understanding of where new American hemp fiber products will be coming from.

It's in that spirit of sharing this article is published.

Lesson #1 - There Are Two Types of Hemp Fiber

Make sure you know what your buyer’s looking for! Do NOT assume when a processor talks about ‘hemp fiber’ that they understand the differences between the two types from both true-fiber cultivars and multi-purpose.

The two types are...

1 - Hemp Bast Fibers | Longer Fibers | 20-30% of Your Stalk

Cultivars of hemp grown specifically for finer-quality hemp fiber high in cellulose and low in lignin can grow from 8ft to as high as 20ft tall with an 8-14ft average for those ruggedly long, pencil-to-thumb-thick and ultra-durable greenish bast fibers - 70-90% of total fiber.

These are the primary fibers you’re after.

Secondary bast fibers, the smaller portion (10-30% total fiber), come from either dual purpose grain + fiber hemp or hemp CBD crops. They’re shorter with higher lignin content.

Note: when we call a hemp crop dual purpose, this typically means it’s a grain crop with lots of biomass and fiber leftovers which shouldn’t be wasted but transformed into countless consumer and industrial products.

2- Hemp Hurd | Shorter Fibers |The Other 70-80% of Stalk

When you loosen and separate the outer bast fiber, inside you’ve got white and creamy-colored woody hurd much higher in lignin content. These are shorter lower quality fibers but can have variable values as applications for the fibers and higher lignin content emerge. A great replacement for wood chips, applicable for pyrolysis and displacing the need for wood-based lignin.

As the 2020s progress a large assortment of applications will emerge for the great buffalo plant. Just be sure if you’re growing for fiber you and your buyers are on the same page.

Lesson #2: Seeding Rate Determines Bast-to-Hurd Ratio

The thicker the stalk, and they can get THICK, the more hurd. We’re seeing hemp CBD varieties with baseball bat-thick stalk already. True-fiber hemp on the other hand needs to be quite thin depending on the specific bast-to-hurd ratio you desire.

This ratio can be manipulated through your seeding rate. As it increases the focus becomes more and more on longer bast fibers over thicker-stalk hurd. More seeding means more plants, less room for stalk and quicker growth into the sky thanks to increased competition (also lends itself to better canopy growth for weed control).

Why is Hemp Lignin Special?

Hemp hurd, or shives, are high in lignin. The amazing thing here is as a resource, hemp is preferred for a large assortment of environmental reasons (especially when we talk about CO2 biosequestration; putting it back into the ground) - elite compared to trees or using less renewable resources for applications in concrete/asphalt, epoxy resins, plastic polymers, carbon fibers, foams, fiberboards, papers, particleboards, fiber-based insulation, and on and on and on.

Why is Hemp Cellulose so Eco-Friendly?

One of the most profound impacts hemp cellulose will have on the world as an easily-renewable and ecologically-friendly crop, is through hemp bioplastics. Here’s a little snippet from an article we published on the subject entitled, “Hemp Bioplastic and You (How To Teach People The Basics)”:

“As arguably the most efficient source of plant-based cellulose, hemp is an ideal bioplastic crop, it can be grown primarily for food and fiber, is superior when it comes to atmospheric CO2 capture, and commercially requires less water and petroleum-based chemicals than conventional crops like corn, soy, or sugarcane (fertilizers, herbicides, pesticides) to reach higher levels of biomass production.”

Lesson #3: Field Choice - An Important Factor for Success

With hemp fiber farming being unleashed on modern American farmers, many of the prohibition-era mythical characteristics attributed to this plant are being tested. One of those is the ability to mightily grow ‘anywhere inside the poles’ without flinching. So other than antarctica or the north pole, it grows like a champion.

And...while that might be true in most cases (grows like a weed), it’s a very different story if you want to grow hemp fiber or grain commercially for a profit!

Take these following tips to heart:

“The first 2-3 weeks of a fiber crop’s lifespan are most critical - too much rain, moisture, lack of nutrition, or uncontrolled weeds can have dramatic impacts.”
  • Choose the best most productive areas of your fields to grow for high-quality hemp bast.

  • Fields where weed pressure is going to be at its lowest because of harvesting methods.

  • Organic growers will need to take weed control even more seriously.

  • Watch for early rains, hemp will sit until it dries out, giving weeds an early edge.

  • Stay away from fields with a history of mold, or rotating after mold-friendly crops.

You want a well-drained area without too much compaction. A nifty upside of growing hemp is that the plant acts like a beacon alerting you to problematic areas in your fields due to low fertility, diseases, over-saturation, etc.

Lesson #4: Climate & Soil Considerations for Hemp Fiber

Speaking of well-drained, moist, unsaturated and highly-aerated soils, you’re looking for the sandy-loamy kinds. In some regions hemp fiber will just be downright too difficult to grow and farmers will lean naturally towards dual purpose or CBD. One of the big deciding factors will be the heavier clay soils that remain saturated longer and increase seedling disease and mortality so high as to skirt economically feasibility.

  • Soil Temp: For fiber you’re looking for 45-50°F; closer to 45 at planting.

  • Optimum Air Temp: Sunnier climates and summers are best at ideal temps of 65-75°F.

Lesson #5: Basics of Planting Hemp Fiber Crops

True-fiber hemp crops are typically grown on large plots. Smaller plots are more friendly to dual purpose and CBD crops. Similar to hay or other forages, planting hemp fiber fields is done via seeding, a mixture of male and female (reproduction happens through male pollination), at roughly 40-60 pounds per acre. This is about double what you’d plant for hemp grain crops because you want those longer, thinner, more desirable bast fibers (and better weed control).

  • Farmers across the U.S. are using a number of different methods, but generally speaking you can use grain or air drills, broadcast seeders, even brillion seeders but there are variables to consider.

  • Male pollen shed will last anywhere between 2 and 4 weeks and then they’ll die. Come harvest all you should have are females.

  • Because hemp’s a photoperiod-dependent crop, a short day crop, flowering triggers with the summer solstice (June 21st) and shorter days. Afterwards comes the reproductive phase.

Planting Specifics

Once you’ve got your firm and shallow seedbed, use a roller or packer for great seed-to-soil contact at a depth of 1/4th to 3/4th inches (aiming for a ½ inch). Again, for fiber it’s going to be anywhere from 40 to 60 pounds of seed per acre, but this will likely change as the industry rapidly progresses and farmers create first-rate genetics to what we have today.

Hemp Fiber Planting Date - AFTER a Rain, Not Before

Shoot for April to May with soil temp in mind, and remember the longer it’s in the soil and able to grow the better. Just make sure it’s AFTER the last potential heavy rain. If you see or hear of some rain coming don’t try and get the seed in the ground before...wait out the rain, then plant. Many farms in states like Wisconsin are planting for fiber in the last week of May; first week of June.

Lesson #6: Water Needs of Hemp Fiber Crops

Cannabis requires a fair amount of water to create magnificent bamboo-like shoots of incredible bast fiber and hurd 16 feet high (well, along with plenty of sunlight and CO2). Below ground the roots can reach out for 1 to 2 feet - longer during drought conditions than wetter.

Both irrigated and non-irrigated fiber farms have been studied in America, Europe, and Canada and hemp’s a drinker, thus irrigated performs better in terms of sheer quality fiber output but there are of course supply chain and environmental considerations.

  • During its rapid growth stage (30-45 days after planting) you can almost watch it grow with the naked eye at 1-3 inches a day.

  • This rapid growth can be accelerated through increased seeding rate, good seed preparation/germination, EXCELLENT field choice and cooperative weather.

  • Moisture Requirement: Min of 10-15 inches - Purdue’s Hemp Project reports most varieties require 25-30 inches of rain, especially in the critical early weeks - while Ontario reports half the crop’s water usage occurs during flowering, although we don’t want seed set for fiber.

Hemp fiber crops aren’t guzzlers, but they’re thirsty. They like regular drinks, but drought pressure can be handy too. Another one of those mythical characteristics that haven’t lived up to reality is the idea hemp fiber can be a good dryland crop - it’s not really a good performer without abundant rainfall!

Lesson #7: Typical Fertility & Nutrient Demands

Marginal soils with lower fertility should be avoided because it’s hard to be profitable. You can get great use out of marginal soils with hemp, but not if the highest-quality bast fibers are what your buyers are after. Farmers must keep in mind the levels of fiber competition which will be coming online between 2020-2030.

In the first weeks of growth nutrient demand continues ramping up until the summer solstice triggers the flowering stage. Along with a pH of 6.0 to 7.5, here are the general nutrient demands of true-fiber hemp crops but it’s going to be different for different varieties in different regions.

  • Nitrogen | 40-60 lbs per acre | Boost Rapid Growth Stage | Supports Bast Fiber

  • Phosphorous | 40-70 lbs per acre | Seed Storage

  • Potassium | 250-350 lbs per acre | Stalk Storage & Rapid Bast Growth

  • Sulfur | 15-25 lbs per acre.

Be aware of what hemp fiber’s going to take from the soil and what gets put back during the open-field retting process if that’s what your operation is suited for.

According to the Canadian Hemp Trade Alliance,

“Hemp removes or uses a total of 200 actual kg/ha of nitrogen; 40 kg/ha is removed in the seed and 160 kg/ha in the stalk. If the hemp is grown for both grain and fiber production, there will be a large amount of nitrogen removed from the field…”

What is Field Retting with Hemp?

The simplest way we’ve heard it put is that hemp retting is a form of controlled rotting after cutting in dry weather that lasts 2 to 5 weeks where you let nature (microbes) help break through the bast fibers. What’s happening is a degradation of plant pectins or cell walls/intercellular tissues that keep the outer bast fibers glued to the inner hurd-core.

Hemp retting does require some moisture to do its job properly, but no downpours. You’re looking for wide swaths for retting uniformity and moisture more along the lines of heavy dew or foggy conditions. The process also helps put lots of nitrogen (hemp leaves are around 50% nitrogen) and potassium back into the soil.

Lesson #8: When to Harvest Hemp Fiber Crops

If you’re a prudent and responsible fiber farmer, get into the habit of walking or scouting your fields at LEAST once a week to look for issues your hemp is trying to bring to your attention. Because you’re going to be mowing the hemp, don’t let your fields spring any surprises on you.

You’re going to harvest within the first 1-2 weeks when you see pollination begin - towards the end of July into the beginning of August. You DO NOT want seed set for true-fiber production because seed set increases lignin content. Remember the more hurd-lignin content, the more you’re lowering bast-cellulose content.

  • Once you see the males dispensing their pollen, shoot to mow at 10-20% pollination!

  • Leave 4-6 inches of stubble to dramatically lower ash content.

  • Avoid the stalks sitting on naked soil to further reduce ash contamination in stalks.

If you opt for disc mowers, don’t use conditioner. Leave the stalks intact without being damaged, or, what some farmers use is an old school straight sickle mower but you’ll need to be ready to keep those blades sharp. Hemp fiber does a number on blades rather quickly…expect regular maintenance on any cutting equipment.

Raking Considerations

Expect to go through your crop (which should be in a nice wide swath) between 1 to 3 times to help stalks turn from light green to a pale yellowish depending on how the weather is cooperating and how the retting process progresses over 2 to 4 weeks.

Your goal is a nice even drying and retting process.

  • Because of the incredible amounts of biomass and stalk, windrows should be as wide a your baler pickup width and at a height you can manage without bunching up stalk under the tracker.

  • Remember, you could be growing stalk 12-18ft tall that’s been the standard for durable plant fiber for LITERALLY thousands of years. Canadian farmers will be the first to tell you how demanding it can be on machinery - watch for combine fires and breaking equipment because of fiber-wrap (especially the PTO).

Expect to use some type of inverter to completely flip stalks end over end, which can be a challenge but PTO driven rotary rakes have been leveraged successfully in areas of the country.

Lesson #9: Square Bales - Stored at 10-15%

Shoot to store your square bales at generally 10% moisture until shipped. If you don’t have instant-ship setups with buyers, or any buyers at all yet and you’re experimenting, be prepared to store bales out of the elements (ideally under cover off the soil) to keep them dry for potentially a month or two.

Why large square bales? Because they’re easier and more efficient to transport and easier at this point for the few American hemp fiber processors out there to do their jobs. Due to the relatively new and evolving processing infrastructure, your hemp fiber bales may need to travel quite a ways!

Weed Contamination Can Become an Issue

Processors are only interested in your fiber, not ash or weeds. Expect processors to be picky, especially if you go through the hoops to become a certified organic hemp grower. Play it safe - don’t bother raking and baling overly weedy areas of your fields.

Imagine what would happen, let’s just say, if a couple extra weedy bales happen to be the bales tested by a processor and because of these few bales your ENTIRE load is rejected. It can happen. It’s already happened. It’s happening to someone right now somewhere....

Processors are going to be few and far between for a while so they have all the leverage, don’t send them weedy or ash-encrusted bales of hemp fiber.

Lesson #10: Processing & Money Making

This CANNOT be overstated - for years to come American hemp fiber farmers need to take good care of their bales. Processors will likely have little to no cleaning mechanisms - simply tearing your bales apart and sending them through their machinery.

Do everything you can to reduce mold, stones, loose gravel, dust and debris, because if your hemp damages their machines you could find yourself without ANY well-paying processors lickity split!

Don’t stack your bales on bare soil, dirt or gravel.

  • True fiber-type yield is generally going to be 4-6 tons/acre.

  • Dual purpose grain-fiber comes in at roughly 0.5-2.0 tons/acre of fiber.

  • Quality control and focus on buyer-determined fibers is CRITICAL!

  • Determine what your buyer wants - what’s their end product?

  • Gross production for conventional crops is around 1200-1400lbs per acre with organic at 600-800lbs per acre (late 2019 numbers). This is all dependent on your region, genetics and farming methods which will be evolving quickly over the next decade.

Now go farm some hemp fiber…please...

The end of cannabis prohibition and the rise of hemp farming in this new millennia is truly exciting. Farmers are on the front lines. Do what you can to support them. If you’d like to support them through us, well, you can always cast your lot with the Darby Hemp crowd.

What's Darby Hemp About?

Human societies are only as strong as their resources. Our platform is inspired by the desire to support a resurgent American hemp industry - its people, its economic impacts, its environmental promises.

Rather Read in Email?