Master dry back! Controlled substrate drying for beginners and advanced users

The key to success in indoor growing is the balance between light, nutrients and humidity, and regular drying of the substrate is an important tipping point. The so-called dry back is a technique that consists of controlled drying of the growing medium between individual waterings. In today’s article you will learn why dry back is important and how to effectively use this technique in your grow room.

Not only novice growers often ask how frequently they should water their plants. Unfortunately the answer is not as simple as it may seem at first glance. If you have been growing for some time, you have likely noticed that the frequency and amount of watering significantly affect how plants develop. If you water too often and the growing medium is constantly saturated with water, plants are not forced to expand their root system and ultimately their ability to absorb nutrients decreases. On the other hand, each time the substrate dries out, plants create new roots in an effort to obtain water, which after watering can absorb even more water and nutrients. Plants regularly exposed to dryness are more resilient, show more vigorous growth and, according to some studies, also produce a higher amount of secondary metabolites (terpenes, flavonoids, active compounds) than those grown in a constantly moist medium.

How to use dry back

Understanding why regular drying is important is not difficult, but the practical use of the dry back technique can be a challenge even for experienced growers. Different growing media retain water differently, and the speed of substrate drying is influenced by environmental factors such as temperature or air humidity. Last but not least, it is also important what growth stage the plant is currently in. A different dry back is suitable for clones, vegetative or flowering/ripening plants.

• Coco substrates dry relatively quickly while holding a large amount of water. It is also important that the coconut fibers do not dry out completely during dry back, because they then lose their retention properties. When growing in coco we usually water at most once a day or less often.
• Soil and potting mixes dry slowly and dry back can take longer than with coco or hydroponic media.
• Rockwool dries quickly and can hold a large amount of water, which allows frequent irrigation interrupted by short dry back windows. From the perspective of irrigation control, mineral wool enables better influence on plant growth than other growing media.

Want to learn more about how the choice of growing medium affects your plants? Read our Guide to growing substrates.

Besides the growing medium, another important factor affecting dry back is the age of the plants. During vegetative growth plants need more water than they do during flowering and ripening. Excessive drying during the growth phase stresses plants and slows their growth. On the other hand, during flowering and ripening a gradual increase of dry back is desirable. Mild stress forces plants to flower and promotes resin production. However, it is necessary to take into account that during flowering and ripening we usually maintain lower relative humidity in the growing space than during the growth phase. Air humidity and temperature also affect how quickly plants transpire and absorb water. When you consider how to use dry back in your grow room, remember that it is primarily a balance between overwatering and the stress caused by lack of water.

Did you find today’s article interesting and want to learn more about indoor growing and the latest gardening techniques for outdoor and urban growing? Don’t hesitate and visit our Higarden blog!