Generally speaking, growers want their marijuana plants to grow big and beautiful, and provide the biggest yield possible. However, sometimes plants can become too high, quickly cramping out a grower’s space and possibly even causing harm to the plants. This is known as over-stretching, and while over-heating is one cause, it’s not the only one. It’s important that growers are aware of the problem so they can be on the lookout for it, try to prevent it, and know how to fix it if over-stretching does occur.

Causes of over-stretching and over-heating

Light and heat are the most common reasons for over-stretching and over-heating marijuana plants, however there are a number of others including:

  • Genetics. Some strains are just designed to grow taller than others. Sativa strains for example, are known for their long, lanky stems so this needs to be taken into consideration if space is an issue.
  • The flowering stretch. When plants make the transition from the vegetative stage to the flowering stage, they can go through a “flowering stretch” that can add inches, or even feet to a marijuana plant. This is a natural phase and if growers are aware of it, they can even use it to their advantage.
  • Heat. If a grow space becomes too hot, plants will start to stretch and grow longer stems.
  • Light. Light is one of the biggest causes of over-stretching. Red and orange light will encourage stems to grow upwards instead of out, making them very tall, as will high-pressure sodium lamps. Also, if the lights are too far away, plants will stretch up in order to access the light they need to grow. However, if the lights are too close, it will create too much heat around the plants and stems will also start to stretch. This is a very delicate balance.

How to fix over-stretching and over-heating

Over-stretching and over-heating can be a problem for marijuana plants. However, once you’ve identified it, it can be very easy to fix.

  • Adjust lights. Because lighting is one of the biggest causes of over-stretching, it’s important to adjust them as needed. If you’re using CFL or HPS lights, check to see if they’re too hot by placing your hand right over the plant and leaving it there for several seconds. If the light is too hot for your hand, it’s also too hot for your plants and so you need to move your lights farther away. CFL and fluorescent lights should be kept 4 or 5 inches away from your plants. LED lights typically need to be placed 12 to 18 inches away, but if they’re very powerful, they might need to be placed even further away.
  • Adjust heat. Over-heating is the other most common cause of over-stretching and so, cooling the space is important. Create air circulation in the room so that the plants can bend, forcing their stems to grow stronger and wider. Air-cooled lamps can also be used, which will prevent the lights from getting too hot. Keeping the lights on during evening periods and off during the daytime can also take advantage of the cooler air, keeping it from getting too hot during the day.
Cannabis grow with fans

Of course, the best way to fix the problem of over-heating and over-stretching is to prevent it from ever happening at all. This can be done by keeping the grow space at a temperature of around 60 degrees Fahrenheit using either an air conditioner, fans, or air vent tubing that will move the hot air outside. Pruning can also help as removing excess foliage will allow both light and cool air to circulate around every inch of the plant.