Growing basil in hydroponics

4 min read

Growing basil in hydroponics

Presentation of basil

What is basil?

Young Thai basil grown in a DWC system.

Basil is a herbaceous plant grown mainly as an aromatic plant. Originally from tropical Asia, it then spread throughout the Mediterranean basin. There are different varieties of basil. The best known being Ocimum basilicum , which includes common basil and its many well-known cultivars (great green basil, Thai basil, purple basil, etc.). We can therefore group all varieties of basil into two distinct categories:

  • annuals: Ocimum basilicum
  • perennials, or perennials: Ocimum kilimandscharicum (Kenya basil) and Ocimum tenuiflorum (holy basil, tulsi) are the best known.

The life cycle of basil

First basil flower grown in DWC.

When it comes to cultivation, all varieties of basil like hot, sunny areas. In our temperate climates, it will therefore have a life cycle in 3 stages:

  • the growth stage: this is the first stage in the life of basil, the production of leaves is important. This is the best time to harvest crops for consumption.
  • the transition stage: leaf production is slowed down, there is much less available for consumption. It is at this time that we can make cuttings.
  • The stage of production: No more leaves are produced, giving way to a pretty flowering.

Annual basil varieties will die after flowering. It will therefore be necessary to sow seeds anew each year. You can collect them directly from the flowers once they have dried.

The perpetual varieties of basil, on the condition that they are placed in a room with a minimum temperature of 10°C in winter, will go into dormancy to resume their growth in the spring.

If, like Jardin Futé, you are in an area with a well-defined cold season, it becomes interesting to grow it indoors under horticultural lighting during the less favorable seasons and take advantage of the summer heat to produce it in outside.

How to grow basil in hydroponics?

Root system of a basil grown with the Kratky method.

Basil adapts to any kind of hydroponics. You still need to provide it with a fairly large tank because it is an herb that has a very vigorous root system. Improper watering is one of the main causes of the loss of your basil. In a pot culture, the soil must be both moist and not very saturated with water. The drought is fatal to him. Therein lies all the difficulty. That is why in a hydroponic culture you will no longer have to worry about these waterings. The plant drinks what it needs, when it needs it.

Materials required

To successfully grow basil in hydroponics, you need:

  • hydroponic system
  • horticultural lighting (for indoor cultivation)
  • hydroponic fertilizers
  • pH up or pH down
  • pH meter
  • Conductivity meter (EC-meter)

Germination of basil seeds

Young basil plant installed in a DWC hydroponic system.

To start your basil culture in hydroponics, you must start by germinating your seeds. We advise you to use rock wool cubes for your seedlings, this substrate is ideal because it can then be transplanted into any hydroponic system.
Find our article on sowing in rockwool cubes to find out all the steps to follow.

Then the basil needs a certain heat to germinate properly. We suggest using a heating mat. Germination takes place in only 3 or 4 days, whereas in an unheated greenhouse, it takes about ten days.

Finally, when the cotyledons appear, the young seedlings must be transplanted into a hydroponic system with a nutrient solution adapted to them.

Preparing the nutrient solution for basil

  • Add water and fertilizer to the tank until an EC of about 0.8 is reached.
  • Then adjust the pH so that it is between 5.5 and 6.0.
  • After two weeks of cultivation, it will be necessary to gradually increase the quantity of fertilizer to finally obtain an EC of 1.8 at most.
  • Keep your pH acidic, between 5.5 and 6.0 throughout the grow.

Caring for and harvesting your basil in hydroponics

There is a technique for pruning basil correctly and enjoying it for several months.

Simply cut the tallest stems above a node. The node being the place where the leaves and the future branches are formed. By cutting like this, each branch will split into two new branches. On the other hand, it is advisable to leave the oldest and largest leaves, they help the plant to reform its new stems more quickly thanks to photosynthesis.

By following this technique, the number of branches on your basil will multiply and the harvests will be even more impressive each time.

Example of a basil pruning zone

One last thing about basil pruning, it is very important if you want to delay the formation of flowers as much as possible. Indeed, we have seen that in the life cycle of basil, flowering is the last stage. By pruning regularly, you therefore extend the life of your basil.

Growing hydroponic basil outdoors without horticultural lighting

Growing basil outdoors is possible as long as temperatures allow. In order to obtain a good development of the plants, the light exposure is an essential criterion. If you place your basil in a shady area, it will still grow, but extremely slowly. This is why a good exposure is very favorable to it. In summer, place it in full sun. Protect your hydroponic tank well from the sun’s rays to limit the development of algae. When the temperatures no longer allow you to keep your basil outside, choose a window sill facing south preferably.

Indoor basil photoperiod and light cycle

Evolution of a basil plant grown with the Krakty method indoors.

By knowing the life cycle of basil, we quickly understand that the use of horticultural lighting becomes necessary to enjoy it all year round, but which photoperiod to choose?

Basil can grow under different light cycles. Polish researchers conducted studies on the influence of temperature and photoperiod on the growth of basil plants. They therefore cultivated them under 2 different photoperiods (12 hours of day / 12 hours of night and 16 hours of day / 8 hours of night) with different temperatures (day/night: 25°C/20°C; 23°C/ 23°C; 20°C/25°C). They showed that with a photoperiod of 16 hours of daylight plant development was greater than with 12 hours of daylight, but only for a temperature of 25°C during the day and 20°C at night. The other temperature ranges did not show such a difference in development.

It is therefore possible to cultivate basil with a photoperiod ranging from 12 hours to 16 hours of daylight. In the end, the most important thing is to offer heat, around 25°C, to your foot during cold periods because the cold slows down its growth, even being fatal to it.

In addition, thanks to our experience, we have noticed that with a photoperiod of 16 hours of day and 8 hours of night, the plants begin to flower after 2 months of cultivation.

Know that when basil begins to produce its flowers, it no longer produces leaves. It would therefore be interesting to know after how long basil flowers with a photoperiod of 12 hours of daylight.

Basilisk: Kratky vs. DWC

Comparative diagram between the two hydroponic systems, Kratky and DWC.

We tested two types of indoor hydroponics for this plant:

  • Kratky method , with lemon basil
  • DWC , with Thai basil

They were then placed under a horticultural LED lamp. Then, after 4 weeks of cultivation, a first pruning made it possible to obtain a hundred grams of leaves. The basil is very vigorous, it was enough to wait a week after each pruning to have a similar harvest.

At first, the basil grown in DWC had a slightly faster development than in Kratky. But after 6 weeks of cultivation the harvests were similar in the two systems.

And as a bonus, the Pesto recipe

Ingredients :

• 100 g of fresh basil leaves

• 60 g of parmesan

• 60 g of pine nuts

• 2 cloves garlic

• 25 cl of olive oil

• 2 tbsp Guérande coarse salt

Preparation of pesto

Preparation :

  1. Insert all the ingredients one after the other into a food processor.
  2. Mix everything and reserve in a jar. Your preparation can be kept for 10 days in the refrigerator.

Gourmet tip: For more flavor, choose a variety of lemon or aniseed basil. Your pesto will taste it.

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