9 Top Tips to Consider When Growing Autos Indoors

12 Nov 2023

Once upon a time, autoflowering Cannabis plants were popular for planting outdoors and in greenhouses, with excellent results. However, in recent years, many growers have decided to plant autos indoors to get the best possible yields and top quality buds. In this article, we provide 9 top tips to consider when growing autoflowering plants indoors, to help you become the best grower possible and master the world of autos.

What Are Autos and How Do You Grow Them?

Unlike photoperiod Cannabis plants, which require 12 hours of dark and 12 hours of light to induce flowering, autos have the genetic ability to grow into a bushy plant and begin to flower regardless of the darkness period. The average flowering time from seed to harvest is around 75–90 days, and yields of 25-40g per plant dry are easily achievable.

When grown outdoors during May until July, autos can thrive under these conditions and will often grow to around 90 - 125 cm tall and produce top shelf buds. You can also get away with a healthy auto crop during September to November in a hot climate, making autoflowering plants highly desirable for long seasons and consistent hot weather. 

  • Autos are not light dependent and will flower automatically after 21–28 days.
  • When grown outdoors, autos have proven themselves to be resilient and tough.
  • Easy to grow and an excellent choice for beginner and first time growers.
  • You can now grow an autoflowering version of most photoperiod strains.
  • Some indica dominant autos can flower as quickly as 60 days from seed to harvest.
  • Autos are great for keeping a low profile and stealthy and discrete outdoor garden.

9 Expert Tips for Cultivating Autos Indoors 

Growing auto indoors will give you many advantages compared to growing outside, ranging from intense lighting, long daylight hours and plenty of nutrients. Below are 8 top tips to think about the next time you order a pack of auto seeds and get planting!

Top tip #1 - Large pots are best

The trick with growing good-sized plants that are worth the electricity, time and effort is to get a good root base well established within the first 25 days. Growing autos in a large sized pot such as 20+ litres will produce bushy sized plants with good quality yields. Our top tip here is to think the bigger the pot, then the bigger the plant will be. You will want to avoid repotting autos, so starting off in a big container is best.

Top tip #2 - 16–20 hours of light

There is no set light cycle for growing autos, however many find that the sweet spot is between 16–20 hours of light and 4–8 hours of darkness. Not every autoflowering Cannabis plant will react the same, so our top tip here is to find which light cycle works best and give them at least 4 hours of darkness, to allow the plants to produce sugars for the roots at night. 

Top tip #3 - Avoid topping

Topping photoperiod plants is easy to do and the more time passes, the bigger and more bushy the plants will become. Unfortunately, with autos, this is not the case and there will be a limited window of 28 days of vegetative time. Our top tip here is to avoid topping autos as the final size of the plants can be small and doing so late on can encourage stunted plants once flowering commences. 

Top tip #4 - Use HID lighting

If you really want good results and buds which are so well grown, you would never tell the difference between autos and photoperiods, then use HID lighting. This basically means a 600 watt and above HPS light and ballast, or a high-powered LED light. Our top tip here is to avoid using CFL and low powered grow lights, as the plants will produce minimal yields. 

Top tip #5 - Bamboo canes

One of the best ways to help support heavy side branches, which have a tendency to droop and drown with weight, is to use bamboo canes and plant ties. Adding support around week 4 and firmly tying the side branches, will encourage the autos to really fill out and pack on the pounds during the crucial weeks of flowering. Our top tip here is to insert the canes down the side of the pots to avoid causing root stress.

Top tip #6 - 40% relative humidity

The main advantage of growing autos indoors, is the fact you are able to control and adjust the relative humidity levels of the grow room. During flowering, you will want to lower the humidity levels down to 35-40% to reduce the risk of mould and powdery mildew. Our top tip here is to use a dehumidifier and control the amount of moisture present in the air. Keep your air flow and fans working well for fresh air circulation will pay off massively. 

Top tip #7 - Don’t take clones

One of the downsides of autos is the fact that you cannot keep them suspended in a vegetative state, unlike photoperiod strains, so taking clones is not an option. Our top tip here is to leave your autos to grow once planted, and never take cuttings, as this will only stress the plants out during a key stage of growth and development. 

Top tip #8 - Grow multiple autoflowering strains

Why not grow out as many autos indoors as possible, and expand your horizons. Planting a wide variety of autos from various seed banks is a great way to see how each plant grows, from indica, sativa and hybrids. Our top tip here is to grow out as many as you can, and to have a wide range of flavours and effects labelled in jars once harvested. 

Top Tip #9 - Veg and bloom nutrients

Making sure that your autos have plenty of hard food in the soil and liquid nutrients, will make a big difference in how quickly and vigorously they become. Our top tip for feeding autos is to use a liquid feed designed for the vegetative phase during the first 28 days, then to switch to a flowering bloom nutrient for the remainder of the flowering period. Of course, don’t forget to flush your autos, meaning to feed only plain water for the final 14 days to get the best taste.