Hermaphrodites in Cannabis – Triggers, Detection, Heredity

A hermaphrodite is a female plant with extra male flowers. These flowers carry anthers, small pollen sacs. Their pollen can pollinate the plant’s own buds and its neighbours. Hermaphrodites also appear without stress: in one operation 5 to 10 % of plants showed anthers. The tendency is inherited.

What triggers male flowers?

Four triggers are documented. Cold of about 13 °C shortly before or during the switch to flowering. A short day on young plants. An abrupt change from 18 to 8 or 11 hours of light. And the spray silver thiosulfate, which blocks the plant hormone ethylene. Cold at the switch made 71 % of females in a prone line form male flowers. At 21 °C it was about 12 %. Triggered on purpose, the process is called sex reversion.

Stay well above 13 °C around the switch, nights included.
Hang up a thermometer with a minimum reading.
Switch to 12 hours as usual. No trial turned up on a gradual transition.

What is not documented as a trigger?

Light leaks, pruning, heat and UV. In an operation with 403 plants, light leaks were not linked to hermaphrodites. None of the leaks was bright enough for the meter, though. Pruning gave no more hermaphrodites than no pruning. No trial on heat turned up, and the UV trials did not count male flowers. After watering was cut back, seven females formed male flowers, but there was no comparison group. A light-tight room still pays: even very faint light that extended the day to 15 hours delayed flowering in one cultivar.

With a hermaphrodite, first check the night temperature in the week of the switch.
Then check where the plant came from.
Search the room for light with the lamps off.
Which other stresses in flower change potency and yield is covered in the article on plant stress.

When and where to look for anthers?

From week four of flowering. Most male flowers sit low on the stem and on the lowest flowers. Anthers are small sacs between the little leaves of the flower. The white hairs of the female flower are thin as threads. No trial turned up on plucking single anthers.

From week four, check every week, lowest parts first.
Take a plant with anthers out of the room before the anthers open.

What does pollination cost?

A lot. Pollinated flowers had 60 to 75 % less active compound. Part of the aroma compounds was lost too. Seeds need three to four weeks to ripen. By calculation, anthers that only open in the last two weeks can hardly produce ripe seed. How much active compound such late pollination costs has not been measured.

Take the plant out even shortly before harvest. Released pollen reaches the neighbours.
The earlier you look, the smaller the damage.

Where does the tendency come from, and what does feminized seed change?

The tendency is inherited, with regular and with feminized seed. Feminized seed is meant to give only females. Daughters of hermaphrodites formed male flowers more often, 34 instead of 23 % in one trial. For feminized seed, a female is made into a pollen donor with silver thiosulfate. The spray works however prone she is. So the treatment says nothing about her tendency.

Let mother and pollen donor flower untreated to maturity beforehand.
Drop every plant with male flowers.
The test procedure is in the article on stress testing.