How to Speed up the Growth Cycle

– The growth cycle as I use it in the next few posts means the time it takes to go from seed to fruit/flower. There are other factors to consider besides time until harvest. Size is the first to come to mind, small plants in general will be ready to harvest before big ones. Many indoor growers have limited space and therefore grow smaller plants in smaller containers or simply change the light cycle to induce flowering/fruit sooner. Yield is also an important agricultural trait to consider. Plants that are smaller tend to be harvested earlier and tend to have lower yields. If you let your plants grow for longer/get bigger in most cases you get greater yields. In many cases my goal is to maximize all factors without harming others, you need to decide if one factor is more important than others and grow your plants in a way that is best for you. Please see my other articles on limiting factors (link) if you want more information to help you speed up and improve your grow cycle.

If you already have plants, see my post on vegetative growth and speeding up the growth cycle.  If and when you are starting new seeds please read below.

Speed up the growth cycle Seeds – Shorter seed germination is the first and one of the best ways you can get a real jump on speeding up the growth cycle! Depending on the variety of plant, Warmer temperatures can take 3-7 DAYS off the growth cycle. I use a heat mat.  I like to start seeds using the starter plugs  and I put the whole seed tray on the heating mat. I also have used hot houses with a plastic cover to keep humidity high and sometimes I use a heat mat with small pots when I start seeds in soil mixtures. Keep in mind if the pots are too big the heat won’t get to the seeds. For example, 16 oz. plastic cups are a bit too big to get the heat to the seeds in the top layer of soil in the cup. I have also put seeds on a wet paper towel in a plastic bag on top of a heat mat which also speeds up germination.

YOU SHOULD KNOW, I did an experiment to test the effect of using a heat mat on growing Coleus. As expected, the seeds germinated on the heating mat emerged 2-5 days earlier and the seedlings were bigger for the first week. THEN, the plants without a heating mat caught up, and passed the heated plants. The non-heated plants remained bigger until I potted them all up and moved them to the display area. I suggest you do a similar experiment: If you have room under your light for seedlings try placing some plants on a heat mat and others not on it. My first thought was that the Coleus did not like the heat mat once they were established. When I looked at notes and pictures I realized that the plants on the heat mat were watered more often. Two times a week I would spot water the plants meaning I picked up each plant and watered it if it was lite but did not water it if it was heavy. The heating mat made the plants dry out faster and after each weekend I noticed the plants with the heat mat were always dry (never wilted though). So, it might have been low soil moisture and not temperature the caused the slower growth rate. The lesson learned is that if you do keep soil warmer with a heat mat make sure you keep the soil moist, but obviously not soaking wet (watering link).

Good Growing
Dr. E.R. Myers

Notice the plants on the right (that did NOT have the root warmer) are taller, even touching the light athough I have the light on an angle to make it higher for the non-warmed plants.  You can see the heat mat under the plants on the left.