Autoflowering cannabis: flowering hypothesis and growth conditions

This part of the research is dedicated to flowering mechanisms and growth conditions of autoflowering cannabis.

What are the morphological stages of development in autoflowering cannabis?

Here we can review the available information for one of the famous autoflowering Cannabis Sativa L strains – Finola, according to the producer [1].

  • Emergence of seedlings 5-7 days after sowing
  • First true leaves, day 7-10
  • Second true leaves, day 10-12
  • Third true leaves, day 12-15
  • Forth-fifth true leaves, day 15-25
  • Beginning of flowering, day 25-30
  • Beginning of pollination, day 30-35
  • Peak time of pollination, day 40-50
  • Apparent seed formation by day 55
  • End of pollination by 55-65 days
  • Strong smell from females, beginning day 50-60
  • 30-70% mature seed, day 70-80
  • 60-80% mature seed, day 90-100
  • Male flowers normally dead by day 100
  • Harvest time, day 100-120 after sowing

There are some factors that increase the time until flowering: Nitrogen level: higher nitrogen; Soil condition: rich, moist sand. While other factors decrease the time until flowering: Thermal energy: hot, dry weather; Nitrogen level: lower nitrogen; Soil condition: poor, wet clay; Moisture: drought.

Stressful conditions will decrease the amount of time for flowering to begin and end and this will cause rapid maturation of fewer seeds, which will have low grain yields and poor germination rate.

There are other autoflowering hemp varieties: Fedora 17, Felina 32, Uso 31 (harvest time ~ day 133), Juso 14, Ferimon. [2]

What is triggering flowers formation in plants?

It is known that environmental conditions (light, temperature, nutrients) have effect on flowering, however the exact mechanism that triggers flowering is not clear yet. There are lots of hypotheses.

Recent research suggests a protein, FT-interacting protein 1 (FTIP1), to be involved in flowering process. Lack of this protein caused delayed flowering. [5]

Another researchers discovered protein, CONSTANS, which plays role in flower formation. This protein accumulates in the plant cells during long spring days but it is rapidly depredated during short winter days. [6]

What is the effect of environmental conditions on cannabis grow and flowering?

The exact mechanism of flowering of autoflowering cannabis is not known yet but there is data that environmental conditions could affect flowering time.

According to some authors intense light, high temperature and lack of rain could cause premature flowering in hemp. [3]

Some authors believe that morphological changes are related to cannabis adaptation to different latitude. They suggest that hemp cultivation at low latitude results of early flowering, while high latitude stimulate late flowering in outdoor grow. [4]

In an observational outdoor study, researchers have used commercial Kentucky and native Iowa hemp to study the effect of different temperatures and soil conditions. They have exposed seedlings and their roots to different temperatures as follow:

1 group: Top and root maintained at 30 C (86 F)

2 group: Top at 30 C (86 F) and root at 15 C (59 F)

3 group: Top at 15 C (59 F) and root at 30 C (86 F)

4 group: Top and root maintained at 15 C (59 F)

The researchers observed the following:

1 group: The cannabis plants in this group surpassed the rest with 7 cm and exhibited the greatest stem length and node number but smallest intermodal lengths and stem diameter until maturity. They had the highest amount of leaf ash and absorbed more water than the other groups. These plants started early flowering and early ageing. They flowered 1 week earlier than group 2 and 3 weeks earlier than group 3 and 4. This group showed highest sex reverse rates at photoperiod change (from 16 to 8 hours).

2 group: The number of leaves produced and the total leaf area per plant were smaller than the other groups. They had low fresh and dry weight per plant.

3 group: Plants had maximum stem diameter and greatest intermodal length. The leaves were unusual in appearance – very coarse in texture, large in size, extremely thick and intensively green. They flowered later than group 1 and 2.

4 group: The leaves for these plants were large, attaining the maximum area per leaf of the four series. The absorbed the smallest quantity of water during growth. The plants had the lowest percentage of root dry weight.

Group 3 and 4 were more predisposed to develop female plants. [7]

Another observational outdoor study explores the effect of high content of essential elements potassium (K), magnesium (Mg), calcium (Ca) and nitrogen (N) added to Knop’s solution. The solutions is prepared as follow: 1 g potassium nitrate (KNO3), 1 g magnesium sulfate (MgSO4), 1 g potassium phosphate dibasic (K2HPO4), 3 g calcium nitrate (Ca(NO3)2) in 1 liter distilled water. The researchers have also used solutions, which completely lack these elements.

K treatment
Left – plant fed with K; Middle – plant fed with high K concentration; Right – plant fed without K

Potassium (K): Plants treated with high K were taller than the ones treated with solution without K. This could be explained with the fact that K is utilized by the plants in early growth stage. Plants at high K produced the largest leaves.



Mg treatment
Left – plant fed with Mg; Right – plant fed without Mg

Magnesium (Mg): Similar effect was observed for plants treated with high Mg – they were taller than the plants treated with Mg-deficient solution. Plants with Mg-deficient solution showed chlorosis (leaves were yellow or yellow-white).



Ca treatment
Left – Plant fed with Ca; Right – Plant fed without Ca

Calcium (Ca): Plants treated with high Ca were shorter than the rest of the plants but with dark green leaves and looked healthy. However, plants with Ca-deficient solution were stunted.



N treatment
Left – Plant fed with N; Right – Plant fed without N

Nitrogen (N): During the growing stage plants supplied with high N were as tall as high K plants and had dark green leaves; but after the grow stage the leave were covered with brown spots. Plants supplied with N-deficient solution were very small and of pale yellowish-green color. N-deficient plants produced the smallest leaves. Another interesting result was that plants at high N were female, while N-deficient plants were male. [8]

The research data shows that the growth of the cannabis plants depends on environmental conditions (light, temperature, minerals, etc.).


  1. Finola Development Morphology
  2. Present and future of kenaf as multipurpose crop for industry and energy applications 
  3. Forms of hemp (C. sativa L.) 
  4. Yield and quality of fibre and oil of fourteen hemp cultivars in Northern Germany at two harvest dates 
  5. Scientists discover ‘switch’ in plants to create flowers
  6. Molecular Mechanisms that Trigger Flowering in Spring
  7. Growth responses of hemp to differential soil and air temperatures 
  8. Time factor in utilization of mineral nutrients by hemp 

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