Cilantro (Coriandrum sativum) also known as coriander, is an herb often added to Asian and Mexican dishes. The herb, from the carrot family, produces lush foliage that you harvest before the seedpots and blossoms appear. The seeds of cilantro are hard and may take up to 14 days for germination. Once the sprouts appear and are transplanted into a hydroponic system will start to grow quickly when the required nutrients are available through the water. Often mistaken as different plants, cilantro and coriander are the same plant. Coriander refers to the seeds that are ground and used as a spice while cilantro refers to the flat and fan-shaped leaves. The cilantro leaves have an easily distinguishable different flavor and aroma profile than the ground seeds, but both are often used in the same dish especially in Indian cuisine.

While cilantro flowers are also edible and and often used in salads and sometimes as a garnish. The herb has a limited shelf-life and its flavor and aroma diminishes when it’s being shipped and stored. The delicate foliage of the herb can also be easily damaged so be careful. The limited shelf-life of cilantro and its fragile foliage makes it an excellent herb to grow in an indoor garden to be harvested just before use when its flavor quality is highest.

Due to cilantro’s habit of going to seed(bolting) fairly rapidly you will have to make sure that you select only cultivars that will grow large and quality foliage. In addition to that they also have to be slow to bolt in the warm and protected environment of an indoor garden. Such varieties like Santo, Marino and Calypso are ideal to be grown hydroponically as they are slow to bolt and can be harvested two or three times before the plants need to be replaced.

Cilantro Propagation

Start with soaking a 1-inch wide rockwool planting cubes (Aff.link) in a tray of water for two hours. Then pour off the excess water and drop two or three seeds into the center of each tube. Proceed with covering the tray with a clear plastic bag or sheet of plastic wrap and place in a warm area with indirect light. Cilantro seeds will germinate within five days at 68˚F to 78˚F/ 20°C – 25.5°C, with seedlings requiring warmth above 68˚F / 20°C and also moderate light levels to prevent it from elongation and tall weak growth.

Monitor the seed germination and spray the cubes with water three to four times a week to keep the seeds moist. Once the sprouts appear remove the cover and move the tray to a sunny area. Once you’ve done that make sure you spray the cubes at least once a day to prevent them from dying out.

Once the cilantro plants are 2 inchess tall, assemble the hydroponics system and fill it with with water then turn it on and make sure everything is working as expected. Proceed with adding the required nutrients to the water by following the package instructions for the water volume in the system. Usually liquid fertilizer is about 3tbsp for every gallon/ 3.78L of water in the system. Make sure to add nutrients each time when you refresh or add more to maintain the required level of nutrients for optimal plant growth.

To plant the cilantro seedlings in the hydroponic system you will have to instert the 1-inch cubes into the 3- or 4-inch cubes that fit your system. It’s very important to not remove the seedlings from the small cubes, the design allows you to instert them into larger ones in order to prevent root damage. That’s caused by the taproot that cilantro develops and it doesn’t like to be disturbed.

Now place the halide grow-light system over your hydroponics system and set them at 6 inches from the top of the plants and put the light on for 12 hours each day. As the cilantro grows raise the lights to prevent the herb from being burned.

When Should I Harvest My Cilantro Crops?

For small-scale indoor gardens, cilantro can be harvested as soon as it reaches the young seedlings stage through to mature plants depending on the flavor intensity required. The flavor can vary greatly, the young plants being tenderer and having milder flavor to the older plants especially those about to flower, develop stronger and usually slightly bitter flavors.

Keep in mind that freshly cut due to its high rate of respiration should be used within a few hours of harvest. To make the shelf-life longer it’s best to store it in a plastic packaging at 32˚F in your refrigerator. This will ensure the longest shelf-life possible and prevent it from post-harvest wilting.

How To Protect Cilantro from Garden Pests?

The herb is particularly prone to infestations of aphids and whiteflies, which can become major pests if not controlled early. If the conditions in your indoor garden are hot and dry mites can also be an issue while having high humidty can predispose your plants to bacterial leaf spots and botrytis.

Having good airflow in your indoor garden around the base of dense cilantro clumps will assist with disease prevention. To break the life cycle of many insect pests using sprays containing neem or neem oil are your best choice.

Hydroponic Systems for Cilantro

Cilantro can be grown in a wide range of hydroponic systems, most common being nutrient film technique, aeroponics, DFT(deep flow technique) or shallow substrate systems that are using rockwoold mediums or coco coir (Aff.link). You can also use float, pond, raft or raceway solution culture systems if the provided depth of the hydroponic nutrient solution is at least 5 inches.

You will need to maintain temperatures of at least 68°F / 20°C for cilantro and provide the crops with moderate light levels for recently germinated seedlings increasing to high light levels as the plants mature. Temperature and light as well as the strenght of a nutrient solution are all linked to the concentration of volatile compounds and essential oils in these herbs.

In order to improve the oil content and flavor profile it’s worth experimenting with applying slight stress on the plants with intense, balanced light and electrical conductivity. As a rule of thumb electrical conductivity levels in solution culture should be maintaned at around 1.6 to 1.8. If you have limited space in your garden, cilantro seeds can also be grown as microgreens using specifically designed microgreens mats made for hydroponic use. The herb is harvested in the seedling stage after it develops two to four leaves. Even at this early stage cilantro has already developed its unique flavor in a milder form that’s suited to many culinary uses.

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