northern lights autoflower grow guide

Learn How To Grow Autoflowers: Week-By-Week Guide

Autoflowering strains provide fantastic results in little time, often surging from seed to harvest in as little as 8 weeks. Both beginner and advanced growers will have a fun and easy time raising these varieties.

Learn to grow autoflowering cannabis.

  • 1. How long do autoflowers take from seed to harvest?
  • 2. Light schedule for autoflowering strains
  • 3. A note on pH
  • 4. Autoflowering grow guide: How to grow autoflowers week by week
  • 5. Which autoflower to choose?
  • 1. How long do autoflowers take from seed to harvest?
  • 2. Light schedule for autoflowering strains
  • 3. A note on pH
  • 4. Autoflowering grow guide: How to grow autoflowers week by week
  • 5. Which autoflower to choose?

Autoflowering cannabis plants are hardy, fast, and easy to cultivate in confined spaces. What’s not to love? Learn how to grow them week by week below.


Autoflowering strains typically move from seed to harvest in 8–10 weeks. However, some varieties can take up to 12 weeks to fully mature. Strains such as Bubble Kush Automatic and Quick One fall towards the faster end of the spectrum, whereas varieties like Royal Creamatic and Royal Haze Automatic take a few more weeks to ready their buds for harvest.

Many growers elect to cultivate autoflowers because of their speedy growing rate. Their hardy genetics and forgiving nature also make them easier to grow and therefore more beginner-friendly.

Their impressive resistance to pathogens and pests allows them to withstand the challenges of outdoor growing.

However, their yields aren’t as spectacular as those obtained from photoperiod giants, but, the trade-off for brevity makes the decision worthwhile for most growers.


As the name suggests, autoflowering strains don’t require a change in the light cycle to enter the flowering stage. Many growers choose to keep their autoflowers on a light schedule of 18 hours on and 6 hours off during the entire growing cycle. Other cultivators choose to keep their lights on around the clock in hopes of maximising photosynthesis and growth rate, however, this can get quite expensive.

Because of this unique trait, outdoor growers can achieve multiple harvests during a single growing season. By germinating seeds week after week in early spring, you can theoretically rake in your first harvest after

8 weeks, with subsequent weekly harvests when growing fast strains.


The pH value of your soil will determine how well your plants can access the nutrients within. If the pH becomes too high (alkaline) or too low (acidic), nutrient lockout will occur and deficiencies will set in. Cannabis plants thrive in a soil pH of between 6.0 and 6.5. Use a pH tester to track pH throughout your grow.


Follow the fail-safe week-by-week grow guide below for a quick and easy route to harvest time. We cover all of the parameters and variables you need to consider—at the correct times—to ensure your plants remain healthy, vigorous, and productive.

(Week 1) (Week 2) (Week 3) (Week 4) (Week 5)
(Week 6) (Week 7) (Week 8) (Week 9) (Week 10)


Germination usually takes 1–3 days. During this time, your seeds will activate and send a root down into the soil and a shoot above the surface. To begin the germination process, you’ll need to prepare a suitable soil mix. Autoflowers don’t need as much nutrients as photoperiod varieties and prefer light and airy soil.

You can make your own potting mix using the following formula:

  • 3 parts peat moss
  • 3 parts compost
  • 2 parts perlite, moistened
  • 1 part vermiculture, moistened

After you’ve prepared the mix, add some Easy Boost Organic Nutrition to the blend. These pellets will slowly release adequate levels of nutrition into the soil, providing foundational elements and minerals for the entire growing cycle. Add some mycorrhiza to the soil to help your plants flourish later down the line. These symbiotic fungi will bind to the root system and help your plants uptake nutrients more effectively.

Next, poke a 10–15mm hole into a pot with your soil mix. Sow your seed directly into its final pot to avoid the stress of repotting later down the line. Transplanting causes plants to go into shock, and autoflowers grow so fast that they’ll struggle to recover. Place a seed in the hole and cover lightly with soil. You’ll see your seedling emerge in the next few days.

Environmental factors play a key role in optimal germination. Aim for the following to boost your success rate:

  • 70–90% relative humidity (RH)
  • 22–25°C air temperature

Autoflowering cannabis strains grow fast, remain compact, and offer great results. Use this guide to learn how to cultivate them week by week!

1st Grow in My Garage – Auto Northern Lights in Grow Box Under 400W HPS – 5.35 oz Harvest

by [Name redacted per request]

Quick Grow Snapshot

  • Strains: 3 x Auto-flowering Northern Lights
  • Grow medium: FF Soil
  • Grow Light:
    • Vegetative: 6400k T5 Grow Light
    • Flowering: 400W HPS with digital ballast and air-cooled hood
  • Nutrients or Additives: Fox Farms Soil Nutrient Trio

May 5, 2012: Seeds sprouted
July 29, 2012: Harvest!

Total Time – Seed to Harvest:
85 days (2 months, 24 days)

Final Yield
5.35 oz

View full grow journal below!

Getting Started – Pre-Grow

With space to grow in the garage, I decided to build a grow box and try my hand at growing marijuana, even though I’d never grown anything before.

In addition to learning grow skills, building my box was a big test of my carpentry skills, or lack of skills I guess I should say. I’d never built anything like this before.

Planning My Grow Box

Build grow box out of plywood and 2x2s with 2 chambers so I can swap the plants between the chambers when it’s time to flower.

The dimensions of the box are 4’W x 2.5’D x 5’H.

The grow box cost me about $135 for the lumber, screws, caulk, sandpaper, wood stain, and hinges.

You’ll see how the box is divided into 3 sections. I want to put a vent in the ceiling of the bottom right section and a vent in the top of the wall in the left section so that both of them feed into that top part where my carbon filter will be.

What would be the best way of ducting both of those vents into a single carbon filter?

Choosing The Right Grow Light

I was concerned about heat and light usage for my small space.

I looked at LEDs when I first started my research, but I kept reading things about them being kinda sketchy. A lot of people seemed to think they didn’t live up to all the hype.

I considered using T5 grow lights for both the vegetative and flowering stage (6400k bulbs for vegging and 2700k for flowering) because they produce such low heat.

I was hesitant about using a T5 in flowering, though. Some growers seemed to be getting good results with them, yet I was worried that a T5 was not going to be intense enough to get good yields in the flowering stage.

I decided to go with a 400W HPS light with an air-cooled hood and exhaust fan for the flower chamber. It was hard to resist getting a bigger light, but I knew that a 600W was going to be too big/hot for my space.

Final Setup

  • Vegetative: 6400k T5 Grow Light
  • Flowering: 400W HPS with digital ballast and air-cooled hood
  • Fox Farms Ocean Forest Soil
  • Fox Farms Soil Trio
  • Feminized Northern Lights (from Pyramid Seeds), ordered them from Attitude I probably wouldn’t order seeds from this breeder again. The seeds ended up being an autoflowering strain even though it was advertised as being a photoperiod strain. It all ended up working out, but I would have been happier if I’d received the seeds I ordered.

My First Grow In Pictures!

I started germinating my seeds in a shot glass.

I put the seeds in a shot glass filled with water to germinate them I put the seeds in a shot glass filled with water to germinate them

Seeds have sprouted roots

I’ve got a pack of these pellets to start them in. I did a test run by putting a pellet in a cup of water, damn those things expand!

Here is what I ended up doing, I tried to cut out any extra steps and just put the pellets directly into the soil from the start.

I put bottles on top to help retain extra humidity (like a humidity dome). Here are my ultra cheap humidity domes

Seedlings under T5 Grow Light in Veg Chamber. It’s a steady 85 degrees F in there, no idea about the humidity in the bottles.

Day 7 from seed

Day 13 from seed

Day 19 from seed – Plants started looking a little sick

Leaves started looking sick on Day 19 I thought they may have used up all the nutrient in the soil (I haven’t been feeding extra nutrients until now). I started feeding them with Fox Farms Nutrient Trio.

I also considered it might be stress from the wind of the fan, so I got a lot more careful about blowing air on the seedlings.

With these two changes, the problem seemed to sort itself out.

Day 39 from seed – Moved plants into flowering chamber under 400W HPS

I moved the plants into the flowering chamber with the 400W HPS grow light.

At this point, I continued to keep them on a 18/6 light schedule, which should have kept them in the vegetative stage. I wanted to let the plants get a bit bigger before switching them to flowering.

I did not yet realize that these were autoflowering plants.

Day 41 from seed

Today is also the first day I’ve tried to LST (low stress training). I know it’s generally recommended to start LST earlier, but I was trying to avoid it on my first grow just to see how my yield would be with no training.

I ended up LSTing one of the girls who was getting too tall.

I was surprised to see my plants start flowering (you can see a couple of flowers starting to appear in the picture above).

I’d purchased non-autoflowering seeds. Guess I’ll never order from that seed vendor again. At first I thought I was seeing pre-flowers, but I soon realized my plant was producing full-on flowers.

Then I saw something even more scary, a hermie banana…

On the advice of others, I plucked this single banana and finished flowering my girls. This was the only hermie sac I saw throughout the grow, and I’m glad I ended up finishing the girls because I had a fantastic harvest.

Day 45 from seed – Closeup of trichomes on the buds and surrounding sugar leaves

Day 53 / 54 from seed – Buds are fattening up

The plants in the grow box definitely smell at this point, but it only became noticeable to me within the last few weeks. Even now it’s not too bad, and you would have to be in the same room as them to smell it.

Day 63 from seed

Closeup of trichomes

Day 79 – End… The final days

At this point I still don’t have a fan hooked up to my vented hood and I’ve been relying on a wimpy little one and keep the door cracked open to let the heat out.

For my next grow I’ll have a real ventilation system set up and heat shouldn’t be a problem. I’ve been running my light at half power (200W) for the past couple weeks to control the heat. I’ll have much better ventilation my next grow so I’ll be able to run it at 400W the whole time.

Day 84 from seed – Day before harvest (ready to be cut down)

I’m really happy with how they turned out.

For my 2nd grow I’ll have 4 plants instead of 3 and I’ll be LSTing from the start.

Also, I will finish my grow box by hooking up a fan to my hood (with a carbon filter), and I put mylar up on 2 of the remaining walls where I still need to cut some holes.

My light has only been running at 200W for a majority of the grow because the weather has been so hot and my ventilation sucks.

I’ll be really interested to see how much doubling the light, making all the other minor improvements, and avoiding all my previous mistakes will affect my yield.

Day 85 – Harvest!

I ended up having to go to a pet store and buying some activated carbon to control the smell of my drying buds. I knew it would smell, I just didn’t think that much!

Harvest Final Weight 5.35 oz!

My 2nd Grow in Pictures!

Stay tuned for my second grow in pictures.

Here’s a quick preview…

Are You Ready To Start Growing, Too?

So you’re ready to start your own indoor grow…

You know the space you want to grow in, but you have a few questions…

There’s so many confusing options out there, yet you no longer have to figure it out all on your own.

This quick article will guide you through the whole process.

Get the right equipment for YOUR grow space

1st Grow in My Garage – Auto Northern Lights in Grow Box Under 400W HPS – 5.35 oz Harvest by [Name redacted per request] Quick Grow Snapshot Strains: 3 x Auto-flowering Northern