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How To Grow Hemp

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Article by Paul Benhaim

How To Grow Hemp

Growing Hemp in 2011

Before we discuss how to grow hemp we need to know that hemp is a hardy perennial from the Cannabis genus of plants. Countries vary as to their exact definition of hemp. Commonly, hemp with <1% THC value is considered a non-drug form of the plant (most forms of drug-use cannabis contain over 10% THC). Smoked hemp is more likely to induce a headache than a high!

The hemp plant has many well-known uses; today, we are going to explore the legal farming of this great crop.

Non Toxic Agriculture

Hemp is grown in a very similar way to the drug-use cannabis plant. Both types of this plant look and grow the same way. The great thing about this plant is that it does not need pesticides or herbicides. Compared to cotton, this is important, as cotton uses 24% of the world's pesticides, but is only a 2.4% crop share of the total world market!


Well-fertilised soil is required for a good yield. Hemp has been grown successfully in all types of soil, preferring sandier soils. In general, the better the soil quality, the higher the yield. As with all crops, nutrition comes from the soil itself. This may be why hemp is not a mainstream crop. Hemp fields cultivated in a mono-culture field soon lack the nutrients that only chemicals can provide.

So hemp farming works best as part of a crop-rotation system in a sustainable permaculture environment. Hemp has a deep tap root able to maximise the soil nutrients deep down. Nutrition is returned to the soil efficiently as the leave fall and mulch beneath the plant. A hemp crop can yield 9 tons per hectare in just over 100 days with 2 tons of seed in less than 120 days! Yields are optimal when healthy seed is used and correct spacing is observed during planting. The latitude of the plantation has an important part to play when choosing seed variety. Before the first crop is planted, the existing soil condition should be assessed.


The ideal time to harvest hemp crops depends on leaf defoliation or the correct stage of seed maturity. In general a combine harvester is used to gather seed crops and a mower/cutter for fibre crops. The hemp variety and intended use of the resulting crop can affect the harvest time in a number of ways. There are a number of harvesting alternatives;


This is where the complete above-ground plant is baled for pulping. For some applications such as fibre and hurd/shiv production, the hemp stalk is required complete.


Separation of the fibre from the hurd/shiv is a natural process called retting. The more successful the ret process, the higher quality fibre will result making further processing easier too. There are several types of retting in common use;


  • Dew retting
  • Water Retting
  • Chemical Retting
  • Crailar Enzyme retting


Hemp retting takes between 1 and 5 weeks to complete depending on the process used. Whichever process used, the length of the process is critical in quality hemp fibre production and high yield. Before baling and storage, even retting can be attained by turning the windrows. Before baling and storage, even retting can be attained by turning the windrows. Using an in-field chaffer/sieve (or similar machinery) a cross-contamination rate of 25% can be expected between hurd and fibre.


This is the separation of the fibre from the hurd and usually required a dedicated facility. To be cost effective, such facilities need to achieve high throughput - setup costs often run to $10m. Globally there are only 10 major decortication facilities. For MDF producers, disk refiners are necessary. Scotching, combing and hackling are all usually required for textile production.

Harvesting Operations

Hemp should be cut in the early flowering stage for textile applications or whilst the main pollen shedding process occurs, before the seeds are set. Lignification of the fibre occurs beyond the seed production phase of the plant and results in fibre that is only usable in non-woven industrial products. Lignification of the fibre occurs beyond the seed production phase of the plant and results in fibre that is only usable in non-woven industrial products. This causes lower yields if the stalks are cut after the seed has reached maturity. Seed cropping is generally by cutting the tops of the plant and threshing with a modified combine harvester which runs at high speed. To prevent blockages a narrowed chopper should be utilized. Both conventional and axial-flow harvesting machines can be used to gather a hemp crop. Stalks left out in the field after retting are left until dry, mowed, trimmed and baled.

Weather Implications

The beginning and ending of a hemp crop are very weather dependent. Insufficient rain at the beginning adversely affects growth. At the end of the growth cycle, too much rain causes a ret & rot which can mean significant yield reduction.

Processing & Storage

A "winnower" is the most common method for cleaning harvested seeds. The hemp seed variety grown will determine the size of the clod sieve. Slits of 5-6 mm and elongated 2mm slots are recommended as a starting point. If seeds are improperly treated, it is hard to remove the protective husk (pericarp); but this is important in keeping the THC level low in oil production. Hemp seed should be dried until the moisture content is stable at 12%, storage should be in a low-humidity, cool dark place at around 4 Deg C. This should ensure an 80%+ germination rate for 2 years, with rates decreasing over subsequent years considerably. The stem stub of around 3-4 cm is left in-field and turned back into the soil to provide nutrients for further crops. All parts of the hemp plant are utilized commercially or recycled into the environment. Even hemp dust residue is used to make hemp plastics and biofuels.

Find Out More About Hemp

To find out more about hemp agriculture, industry and products, you can find out more from more hemp books by Paul Benhaim, including;

How To Build A House of Hemp

How to Grow Hemp for Profit

Hemp Fuel and Hemp Biodiesel Guide

The Hemp Textile Industry Secrets

The Hemp Plastics Industry

Hemp - From Food to Fibre

The Hemp Bodycare Industry

Medical Marijuana Industry 


About me: Paul Benhaim is a recognized world-authority in hemp research and development, as well as a published author of Hemp-related books and DVDs. He manages the world’s most popular Hemp web sites and advises a number of international companies and individuals through Start A Hemp Business
Paul is founder of the Australian Hemp Foundation, representing the national hemp industry and state associations in promoting the commercial growth of the industrial hemp industry.
As well as acting as an independent consultant and mentor to those interested in business, usually the hemp business, Paul is CEO and Director of a cutting edge Hemp companies involved with hemp plastic and hemp foods products as well as Principle and Founder of a Hemp School


22 Jul 2010

Last Update: 25 Mar 2011

Article/Information supplied by Paul Benhaim

Disclaimer - Any general advice given in any article should not be relied upon and should not be taken as a substitute for visiting a qualified medical Doctor.