Germinating hemp seeds, growing out the hemp seedlings and eventually planting out strong, well-rooted hemp seedlings can mean the difference between a lackluster and lush crop.
Start with purchasing high-quality hemp seeds. But once you’ve done that it’s time to consider the next step, germinating and growing out healthy hemp seedlings!
Even though hemp is famous for “growing like a weed,” it needs the proper conditions and soil to thrive and produce a healthy and profitable crop. You will put your crop on the path to success by starting with appropriate germination techniques.
Here at Colorado Breeders Depot, we advise growers to consider the following four pro tips for growing out you healthy and vigorous hemp seedlings:
- Choose your germination method.
- Monitor humidity levels.
- Don’t Fertilize.
- Keep Young Plants Warm.
Choose Your Hemp Seedling Germination Method — 3 Options
The Paper-Towel Germination Method
The paper towel method is an easy, proven way to germinate hemp seedlings.
Take two paper towels and soak them in distilled water and place them on a paper plate. Put your seeds on the towels one inch apart, then cover with two more sheets of wet paper towels and a paper plate.
Place them in a dark, warm spot (70 to 90 degrees) and check frequently. The paper towels must remain moist. The seeds should germinate within a few days and can then be planted into a soil medium.
Make sure to transplant the seedlings to a pot as soon as you see them germinating and give them light. Otherwise, they could get “leggy” (grow too big without light) and weak.
Germinating in Water
Germinating hemp seedlings in water is a straightforward and effective way to achieve uniform hemp seedlings, often reaching 90 percent germination rates.
Fill a glass with water (distilled is best) and let it come to room temperature. Then drop several seeds into it. Refill the glass every other day but keep the temperature the same.
You should see the seeds start to crack and begin to make roots. Make sure to plant them before the roots are very long (no more than 3 to 5 mm). Also, be very careful taking the sprouted seeds out of the water. It is easy to break off the roots (which will kill your seedling).
Germinating in Rockwool
Another great way to germinate hemp seeds is by using Rockwool, a perfect environment for germinating and growing out seeds.
Rockwool is made from volcanic rock, basalt and limestone and spun into threads, which soaks up and holds water with the ideal growing environment for starting cannabis seedlings.
However, Rockwool does need to be pre-treated before you plant your seedlings. Its PH is naturally a little too high (the perfect PH for starting hemp seedlings is a PH of 6). Soak your Rockwool cubes in water with a PH of 5.5 (it is handy to have a PH meter to check your PH at this point). If the PH of your water is too high, add lemon juice to bring it down.
Insert one to two hemp seeds into the pre-drilled hole (or make one yourself). Then most growers recommend soaking the cubes in a very light root stimulant nutrient solution. Rockwool doesn’t have any nutrients in it, but you have to be careful because adding too strong of a nutrients rinse can quickly kill your seedlings. If you don’t have any root stimulant, try 25 percent of a recommended nutrient solution for a young growing hemp plant.
The cubes should be placed in a tray and put somewhere warm with adequate lighting. You can also set a heat mat underneath the tray for extra warmth. Your seedlings should germinate in a few days. If you put two seedlings in a cube and both germinate, clip one out to provide enough room for the other to grow.
Germinating Hemp Seedlings in Jiffy Pellets
Another great method for germinating hemp seeds is using jiffy pellets. Jiffy pellets are made from coco coir and expand when you soak them. You can usually buy individual disks, or you can buy a germination tray with them already loaded.
Before planting, soak the disks until they are reconstituted and puff up. Place one seedling per disk.
Some growers will pre-sprout their seeds before putting them into a germinating disk, using either the paper towel or water soaking method. Either way, once they are planted, make sure to keep the jiffy pellets evenly moist. We recommend water them from the bottom, letting the pellets gently soak up water through osmosis. Rather than water from the top down, which can be harsh and disturb the roots of tender young seedlings as they are germinating.
They need constant moisture (but not soaking wet) to grow. We suggest bottom-watering.
You can also plant hemp seeds right in the soil or pot where you intend to grow your hemp plant. However, we do not recommend that method and achieve a much more uniform stand by germinating and growing out your hemp seedlings and then transplanting them to their final location.
Watch Your Humidity Levels for Healthy Hemp Seedlings
Watch your humidity levels; they should stay between 95 and 100 percent humidity. If you have a hard time controlling humidity, try placing a plastic dome over your seed starting tray.
The young seedling needs constant moisture but shouldn’t be drowned. Check your seedlings daily and make sure the medium is damp. Even a few minutes of dry soil for a sprouting seed can kill it.
Don’t Fertilize Your Hemp Seedlings
Do not give your young hemp seedlings nutrients, unless you’ve germinated in rockwool.
Nutrients will kill germinating seedlings. Jiffy pellets and growing trays contain a nutrient-free medium. Also, hemp seedlings are susceptible to contaminants. We recommend only watering with filtered or purified water while your seedlings are young. Also, your water should be 7.0 PH.
Keep Young Hemp Plants Warm
Keep all seedlings warm but in the dark until the seeds have sprouted out of the medium. At that point, they immediately need light placed near to the seedling (not more than a few inches above the growing plant), or they can grow up weak and leggy from searching for a light source.
Make sure to keep your temperatures at about 70 degrees for optimal growth!
At about 20 to 30 days after starting your seeds, you should have healthy, vigorous young plants that have grown roots through their growing medium (this is called root bound). At this point, they are ready to be transplanted to the field or your greenhouse.
At Colorado Breeders Depot, we offer free farm consultation for any hemp grower that purchases our seeds. We can help you create your seeding, planting, growing and harvest plan, including helping you get your seeds off to a great start. Helping our customers have an excellent hemp harvest is what we’re all about.