3-Week Old Autoflower (How Should It Look?) My Experience

Recently, I’ve seen lots of growers on forums worried that their 3-week Autoflower doesn’t look quite right.

In this article, I’ll cover exactly what a healthy 3-week-old Autofloweer should look like, and also go over some common problems (and fixes)

What should an Autoflower look like at 3 weeks?

Sign of a healthy 3 week Autoflower
Signs of a healthy 3-week Autoflower

Ok, so first things first, It’s important to understand that every Autoflower will look different at the 3-week stage.

Some Autos strains will have genetics that grows short and stout, while others will grow a bit more ‘stretchy’.

As long as your growing conditions are good and your Auto looks reasonably healthy, there’s really nothing to worry about.

Here are some signs to look for in a healthy 3-week Autoflower plant:

  • Vibrant green leaves
  • No yellowing or brown spots
  • Upright stem (no bending)
  • No droopy leaves
  • Between 2-5 nodes
Northern Lights Autoflower at 3 weeks old
This is a very healthy-looking 3-week Autoflower (Northern Lights) it has a vibrant green color, multiple sets of fan leaves, around 2-3 nodes, and an upright stem.
5 3 week auto strains
All 5 of these 3-week Autos are different strains. Compared to the first example, you can see that they are growing wide rather than tall. You can also see just how different the growth rates are for each strain when grown under the same conditions. In this example, the grower has most likely just watered them (hence the slightly droopy leaves) The grower has also topped these plants, which is why they have grown so wide.

And here are a few things that are totally normal to see in a 3-week-old auto;

  • It might be showing sex (small white hairs)
  • Growing wide rather than tall
  • Starting to flower (some grow quicker than others)
  • Different strains growing at different rates

3 Week old Autoflower Problems (and Fixes)

Let’s look at some common 3-week-old Auto problems and what I recommend you do to fix them.

3-week Autoflower looks too small

Although this 3-week Auto looks small, it actually looks quite healthy, with vibrant green leaves, an upright stem, and no unusual colorings. The slow growth here is most likely due to underwatering. It’s very easy to underwater a small seedling in a big pot.

If you’re used to growing photoperiod plants, it can’t be quite a shock to see how small Autos grow.

However, it’s important to remember that different Auto strains grow at different rates.

I’ve grown autos before that I thought were very small in the 3rd week and they ended up surprising me with their yield.

So if you’re Auto generally looks healthy apart from being slightly smaller than you expected, then I would probably just keep going and see how things play out.

How to fix a stunted 3-week Autoflower

However, If you feel that your 3-week auto looks very small (less than 2 nodes) then it’s most likely an issue with watering.

  1. Check your watering schedule – Although it’s recommended to plant Autos in large containers to avoid transfer shock, it’s very hard to manage a small seedling in a large pot of soil. Each time you water, the large volume of soil will suck the moisture away from the roots of your seedlings. To make sure your seedling is getting enough water, water in a small circle around the stem only. You’ll also need to water much more frequently than you would if you were growing in a smaller container. As soon as the soil around the stem of your seedling is dry (check by digging your finger into the soil half an inch) it’s time to water again.

  2. Check your humidity – seedlings love a humid environment. Having a humid environment keeps your soil moist for longer and gives your seedling another avenue to get moisture if your soil has dried out. The ideal humidity for a 3-week auto is 65-85%. If your grow room humidity is less than 65% then this could be impacting your seedling growth.

3 Week Autoflower Looks Yellow or has brown spots

unhealthy 3 week atuo
This 3 week Autoflower looks small and has yellowing leaves. It looks starved of nutrients. This Auto has been grown in Coco and not been provided with the nutrients it needs to grow © grasscity

If your 3 week Autoflower looks yellow or has brown spots, it’s usually becuase of one of the following issues:

  • Too much/not enough water – The most common cause of yellowing leaves is too much/not enough water. If your auto is planted in a large container and is yellowing, make sure that it’s getting enough water. You should be watering in a small circle around the stem and watering again as soon as it’s dry.
  • Poor quality soil – the soil you use should be light and airy so that it drains well. Thick or sludgy soil will stop your seedlings getting the nutirents it needs.
  • Not enough light – If your Auto is also strecthing, then that’s a clear sign that your light is not close enough.
  • Incorrect temperature or humidity – Make sure your grow room is between 65-85% humidity at all times, and that your temperature is between 23 to 28°C during the day (lights on) and no cooler than 13°C at night (lights off).
  • Lack of nutrients – If you are growing with soil, you shouldn’t need to add any extra nutrients. However, if you are growing with coco or hydroponics, your Auto seedlings

Tips For Getting Your 3-Week Auto to grow faster (and bigger)

If you’d like to maximize the yield from your Autolfower, then here are 3 techniques that are perfect to start using at the 3 week stage.

1. LST (light stress training)

Low stress training an Autoflower to allow light to reach the entire plant and increase size/yield.

Becuase Autoflowers grow short and have significantly smaller yields than regular photoperiod plants, it’s a good idea to start doing some light LST in week 3. This involves gently bending the stems of your plant toward the side of your grow container to allow the lower branches and leaves to get more light and produce larger colas.

2. Leaf tucking

Leaf tucking
Tucking larger leaves under smaller leaves for better light distribution. © Beginner BUDZ

If you can see leaves that are blocking some of your plant’s bud sites, it’s a good idea to gently tuck them out of the way so that your bud sites have access to light. However, It’s important that you don’t remove the leaves, as they are your plant’s primary method of absorbing light.

3. Topping

topping 3 week auto
Topping a 3-week-old Autoflower to improve light coverage © Beginner BUDZ

Both Autoflower and Photoperiod cannabis strains like to grow straight upwards. This natural growth pattern isn’t great for light distribution, with most of the lower leaves and bud sites being covered by foliage from above. Topping not only forces your plant to grow wider, leading to better light distribution, but it also creates more colas (and potential bud sites) as the remaining growth tips will become their own stems.

Topping is pretty stressful for a cannabis plant, so I’d recommend waiting until your auto has at least 5 nodes before removing the tip. By this time, you plant should have developed a solid root structure and be strong enough to cope with the topping.

Bud sites tend to grow right in the corners of each node, so be extra careful not to damage these when topping your Autoflower.

3 Week Old Autoflower FAQs

Here are some quick answers to common questiosn that people have about Autolfowers at the 3 week stage.

If you have any more, please let me know in the comments and I will update the list.

Should you transfer a 3-week Autoflower?

In general, you should avoid transplanting a 3-week-old Autoflower as you run the risk of stressing the plant, stunting its growth, and making it flower too soon. However, that does not mean that you absolutely can’t transplant them. Just be careful and wait until after they have shown sex.

How much should you water a 3-week-old Autoflower?

At 3 weeks old, your auto should have established roots and be able to handle a full soaking of the container until your see water coming out of the drainage holes. Once watered, you should wait until the soil is almost completely dry before watering again.

What is the ideal humidity for a 3-week-old Autoflower?

The ideal humidity for an Autoflower at the 3-week stage is between 40% and 60%. It’s important not to go below 20% humidity or your plant will become stressed and potentially stunted in growth. Humidity above 90% can increase the chance of unwanted mold and infections

What is the ideal temperature for a 3-week-old Autoflower?

The ideal temperature for a 3-week-old Autoflower is between 23 to 28°C during the day (lights on) and around 13°C at night (lights off) If you live in an overly cold or warm climate, it’s important to regulate the temperature of your grow room when your lights are off by using a heater or air conditioner.

Is it normal for a 3 week old Autoflower to start flowering?

It’s perfectly normal for an Autoflower strain to start showing pre flowers at the 3 week stage. Some will start flowering after 3 weeks, some around 5 weeks, while others can end up taking months before flowering.


I see many growers worrying about how their 3-week Autoflower looks. But the majority of the time, the plant is doing just fine.

If you have any other questions about 3-week Autoflowers, please let me know in the comments below, and I’ll do my best to answer them.

Happy growing


James Alexander James Alexander
Hey, I'm James! The founder and head writer here at GreenBudGuru.com. I started this site to share my passion and knowledge of all things cannabis. I used to work as a budtender in central Amsterdam, and have over 7 years of growing experience.

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