Rosemary is a fragrant herb with a long history.

Did you know it was once used by the ancient Greeks during exams to help improve concentration?

There’s even evidence indicating rosemary improves memory.  

In this article, you’ll learn how to grow rosemary hydroponically.

Rosemary’s woodsy, lemon-pine scent is commonly used for essential oils, while its flavor adds an earthy touch to almost any dish.

The herb is used to flavor everything from dressings to breads to meats.

In addition to its memory and concentration benefits, rosemary is rich in antioxidants, which help with immune and circulatory systems.

Plus, it’s also thought to help digestion and calm an upset stomach.

Rosemary is typically sold in supermarkets dried. But nothing beats the strong flavors of a fresh sprig.

Our Pure Greens container farms grow rosemary all year long using hydroponics.

Hydroponics is a method of cultivating crops that uses nutrient-rich water to feed plants instead of soil.

Our container farms use nutrient-film technique (NFT) and deep floating technique (DFT) hydroponic systems.

Getting Started

Rosemary can be planted from seed or cutting. Either way, start the seeds in a growing medium.

The growing medium is an inert media that provides support for the plant roots in place of soil.

We use rockwool, which is made from spun basalt rock fibers, to grow our seeds.

Rockwool has a naturally high pH, so be sure to soak it in balanced nutrient solution and drain it before planting.

Sow three to four rosemary seeds per rockwool cube or one cutting per cube. Then, place the cubes in a humidity dome.

Keep seeds in the dome for a week or two, or until you see germination. Then, open the vents slightly.

For cuttings, keep in the dome for four to five days. Then, take the dome off for 15-minute intervals and observe how the plants react.

“If they start to wilt, that’s showing that the roots can’t handle the rate the plant is transpiring,” explains Pure Greens Head Grower Andrew Wise, “so put the dome back on it.”

Once the plants are able to withstand not having the dome, they’re ready for transplanting.

For crops started from seed, you can tell that the plants are strong enough for transplanting when the roots are exposed through the rockwool.

“If you’re seeing roots out of the bottom, odds are that they’re ready,” Andrew describes. “Another way to tell is by taking off the dome. If the plants can survive without the dome, they can survive the system.”

Rosemary has a low germination rate of about 30%. As a result, it’s more practical for high-volume growers to start from cutting, according to Andrew.


Caring for Rosemary

Rosemary doesn’t require anything special to grow, so after you’ve transplanted the rosemary to the hydroponic system, you can care for it as you would any other herb.

Our container farms use LED lights to give our plants 18 hours of full spectrum light for photosynthesis.

The pH, electrical conductivity and temperature ranges rosemary needs are similar to other common herbs such as basil.

The amount of nutrient solution it needs will depend on its size and your system, according to Andrew.

The bigger it grows, the more water rosemary will need, but be careful not to let it get too wet for too long.

Too much water can cause root rot, which will kill the plant, Andrew says.

Rosemary is a slow grower, but you can still monitor its health by observing its growth.

“Even though it grows slower, it should still be growing,” he says, adding that if it hasn’t changed in a couple months, there could be a problem.

If you suspect your plant is having trouble growing, use the process of elimination to determine the cause.

Any discoloration, like brown or lime green leaves, can indicate too little or too much water.

Harvesting Rosemary

You can improve your yields by harvesting rosemary frequently.

Prune 6 to 8-inch stems as the plant grows. Pruning regularly will help direct your plant toward growing bushy rather than tall.

Without pruning, rosemary can grow up to 5 feet tall. If it gets too tall for the system, it may be burned by the grow lights.

Harvest up to one third of the plant at a time to keep it to a manageable height, without causing too much stress.

“Every time you harvest a plant, you’re stressing the plant,” Andrew explains. “If you cause too much stress, the plant just won’t recover.”

A rosemary bush grown from seed could take 10 to 12 weeks to be ready for harvest, while a bush grown from a cutting could take 6 to 8, according to the grower.

Continue to harvest as the plant grows.

To start growing rosemary hydroponically, you should start your own container farm!

Visit our Pure Greens website or call us at 602-753-3469 for more information about how you can open your own container farm business.