Critical Mass Strain Review: THC, Effects, Flowering Time & Yield

Critical Mass is an original QCS autoflower: a feminized Critical Mass × Ruderalis cross, 70% indica, with 24% THC, 45 to 50 days of flowering and up to 500 g/m² indoors. This Critical Mass strain review covers its flavour, effects, growing needs and the five real customer reviews on our site, plus what growers commonly say about the Critical Mass family.

Critical Mass strain at a glance

What is the Critical Mass strain?

Critical Mass is an original QCS strain: Quebec Cannabis Seeds is its original breeder, and these are our own genetics, bred in Quebec since 2015 by a grower with more than 35 years of experience.

Critical Mass is one of the best-known names in indica cannabis, and the QCS version is the autoflower: a feminized cross of Critical Mass and Ruderalis, bred by Quebec Cannabis Seeds. It is 70% indica, 30% sativa, carries 24% THC and is ready to flower on its own in 45 to 50 days, with up to 500 g/m² indoors.

This Critical Mass strain exists in other forms on our site too, including a CBD version, but this review is about the autoflower because that is the version this page describes. Its appeal is simple: the heavy, relaxing character that made the original famous, in a smaller and faster plant that does not need a light-schedule change.

Some background from around the web: the original Critical Mass is commonly credited to a Dutch breeder known as Mr. Nice, who described it as a reworked take on an older Big Bud line, and it is often listed as an Afghani and Skunk-type indica-dominant cross. It earned its name from its big, heavy flowers. Many other seed companies sell their own Critical Mass, and their autoflower or photoperiod versions can have different timings and yields. The numbers here are for the QCS version only.

Is Critical Mass indica or sativa?

QCS lists Critical Mass Autoflower as 70% indica and 30% sativa, which makes it firmly indica-dominant. That shows in the plant and in the effect: expect sturdy growth, flowers that are heavy for their size and a strong, relaxing finish. QCS describes the effect as strong and relaxing, in line with the indica side.

A small word of warning from real growers, covered below: the sativa share and the Ruderalis background can still give some stretch in early flower. If you want a clear picture of what an indica-leaning plant tends to feel like, read what indica does to you.

Smell and flavour: earth, wood, berry and citrus

QCS lists the flavour as earthy, woody, berry and citrus, and customers add some detail: one grower noted blueberry, citrus and a hint of skunk. That is a lovely mix of an earthy, woody base with a fruity, slightly sharp top.

Other write-ups of Critical Mass commonly describe pine, earth and a sweet, musky quality, with caryophyllene and myrcene often mentioned among its main terpenes. Terpene content varies by plant and by how you dry and cure it, so use these descriptions as a guide only. A slow dry and a proper jar cure give berry and citrus notes room to come forward.

Critical Mass effects

QCS describes the effects as strong and relaxing, and a customer who bought it for its small size and heavy effect gave it five stars. Consumers commonly report that Critical Mass-type indicas bring deep physical relaxation, a calm, happy mood and sleepiness at higher doses, and many people reserve them for the evening.

Dry mouth and dry eyes are the side effects most often mentioned for cannabis in general, and occasional dizziness or anxiety can happen with strong flower. At 24% THC this is a potent plant, so start low, especially if you are new, and let the effect build before taking more.

How strong is Critical Mass? THC content

QCS lists Critical Mass Autoflower at 24% THC, with low CBD (under 2%). That is clearly in the strong range and a notch above the 19 to 22% most of our cookie-style autoflowers offer, so it is a better pick if you want a heavier hit.

Final potency always depends on growing conditions, harvest time, drying and curing. If you want to go higher still, our seeds over 25% THC are worth a look.

Growing Critical Mass: flowering time and yield

As an autoflower, Critical Mass flowers on its own in 45 to 50 days indoors with no change in light hours. Customers report seed-to-harvest times of about 8 to 9.5 weeks, which fits that flowering window plus the first weeks of growth. QCS lists a yield of up to 500 g/m² indoors and up to 300 g per plant outdoors.

The charts below show the flowering window and the yield ranges from the product page. They are ranges that depend on your setup, not guarantees. For reference, other sources quote higher yields and longer cycles for the photoperiod Critical Mass; those are a different plant from the autoflower described here.

Practical growing tips

The product page and customers agree on a few points. Sow straight into the final pot, keep the medium on the dry side between waterings, and harvest by trichomes instead of by the calendar. Customers say the buds stay well spaced, which helps airflow and humidity, but heavy flowers can still be prone to mold on a damp day, so keep air moving and humidity moderate in the last weeks. Remember that “mold resistant” on our pages means mold tolerant.

Plan for height. One customer expected a small plant and got two tall ones that had to sit on the tent floor, and about 17 days into flower both were around 3 feet and still stretching. QCS advises allowing headroom, topping early or training branches sideways. Heavy flowers can bend branches near harvest, so a little support is sensible. Outdoors, one customer lost two of five seeds to non-germination but still got a high yield from the other three, so sowing a couple of extra seeds is a cheap precaution. See our autoflower seeds guide for the full method.

What customers report

Critical Mass Autoflower has five reviews from three customers, averaging 4.6 out of 5. Here is what they say, including the honest caveats.

• Fastest plant they have grown: one grower praised the growth and flower colours, and expected a harvest around day 50.
• More height than expected: the same grower expected a small plant but got two tall ones, about 3 feet at 17 days into flower and still stretching. They liked the well-spaced buds and the smell.
• Bought for size and strength: they chose this type for its small size and heavy effect, and reported no issues in early flower.
• Best auto they have tried: another customer (4 stars) called it the best autoflower they had tried, with consistent plant size and lots of flower. They noted blueberry, citrus and skunk flavours and harvested one plant at 8 weeks and the rest at about 9.5 weeks.
• Outdoor result with a germination miss: a customer (4 stars) grew it outdoors, had two of five seeds fail to germinate, and got a high yield from the other three, with timeline and effects as expected.

The consistent caveats are stretch and a couple of non-germinating seeds in one outdoor pack. QCS replaces packs that fall below the 80% germination guarantee, so email us if that happens.

Is Critical Mass right for you?

Critical Mass Autoflower is a good match if you want a strong, relaxing indica-dominant plant with 24% THC, a quick cycle and generous yield, and you have a little headroom to spare. It suits both indoor growers and outdoor growers who want a plant that does not depend on the sun’s schedule.

It is less suited to a very low-ceiling closet unless you train it sideways. Browse our autoflower seeds or the indica effects guide, and compare with our review of Fat Bastard if you want to go even stronger.

Critical Mass: frequently asked questions

A note on the numbers in this article: harvest dates, flowering times and yields are ranges, not promises. They vary depending on growing conditions: the grower, the method and the season's weather. No strain is 100% mold resistant. How we set these numbers →

View Critical Mass seeds →