Jouke Piepenbrink, pictured above at a Seed Stocker’s expo booth. Photos courtesy of Seed Stockers.
The Emerald sat down with Seed Stocker’s Jouke Piepenbrink, who won the best seed bank award in 2022 at Canapa Mundi, and at Cannafest in Prague in 2023 and 2024. Piepenbrink breaks down auto-flower seeds, aka autos, and provides his best tips to help growers achieve the best results possible.
Emerald: How would you best describe autos?
Jouke Piepenbrink (JP): An auto plant starts flowering automatically about three to four weeks after germination, without needing a change in the light cycle. These plants typically finish in around 11 weeks, regardless of how many hours of light they receive per day.
Emerald: What is the history of auto-flowering genetics?
JP: The auto-flowering gene naturally exists in the wild known as cannabis ruderalis. A separate species native to [regions of Russia such as] Siberia. Due to Siberia’s short summers, the plant evolved to flower quickly before the cold set in.
Emerald: What is the breeding process for autos?
JP: Autos are developed by introducing the auto-flowering gene from cannabis ruderalis into a non-auto-flowering strain. This sounds simple, but it’s a long and meticulous process, as the auto-flowering trait is recessive.
Emerald: Which pot size is best to use for the biggest plants and yields?
JP: It depends on your goals. Some growers have achieved surprising results with very small pots, like those used in the popular Solo Cup Grow Challenge. It’s amazing to see how much you can yield from such limited space with autos.
For those aiming for larger plants and higher yields, a container between 1 to 5 gallons is recommended. This size provides enough root space for the plant to thrive without overwhelming its auto-flowering timeline.
Emerald: Is there an optimal lighting regime indoors for autos?
JP: Autos can thrive with anywhere between 12 to 24 hours of light per day. But for optimal results, we’ve found that 18–20 hours of light per day is best. This balance provides strong growth and high yields.
With 24-hour light cycles, we haven’t seen any real increase in yield or quality. It just wastes energy. So, if you want to maximize efficiency while keeping plants happy, just stick to 18–20 hours of light per day.
Emerald: Which nutrients are best to feed autos from seed to harvest?
JP: You don’t need a special nutrient plan, as autos thrive on the same nutrients as photoperiods, just in lighter doses. If you’re using high-quality organic soil, extra feeding is minimal since the soil already contains most of what the plant needs. Use mycorrhizal fungi and beneficial bacteria to boost root health and nutrient absorption.
A light organic feed is enough, and If using a slow-release fertilizer, plants will get steady nutrients without overfeeding. Slightly increase phosphorus and potassium to support bud development. When using rich organic soil, just add water and microbes, as nature takes care of the rest.
Emerald: When is the best time to plant auto-flowering plants outside and why?
JP: It depends on your location. For outdoor growers, the best planting time varies by hemisphere. May is ideal, but the key is consistent temperatures above 68°F. This ensures flowering happens in peak summer, maximizing light and warmth for top-quality buds. Check your local weather, as warm nights and stable temperatures above 68°F mean it’s go-time!
Emerald: What are your top tips for anyone growing autos outdoors?
JP: Start with plenty of root space, because autos hate transplant stress. If you must move them, carefully cut out the bottom of the starter pot and place the plant directly into a larger one. Cold nights will stunt growth, leading to smaller plants, so wait until nighttime temps are stable before planting.
The more direct sunlight, then the better the yield, so pick the brightest spot available. Autos allow continuous harvests, meaning If you add one plant every two weeks, you’ll have a new harvest every two weeks, allowing a steady cycle of fresh buds and harvests.
Emerald: What are your top tips for anyone growing autos indoors?
JP: Keep it simple and efficient so forget about changing the light cycle. Unlike photoperiods, autos don’t need a change in lighting hours. Keep a consistent 18–20 hours of light throughout the entire grow. Autos plants don’t like the cold. Therefore keep the grow room temperature stable for optimal growth and yield.
Start a new plant every two to four weeks, so you can harvest every two to four weeks for a steady perpetual harvest. Since autos don’t need different light cycles, you can grow all plants in the same tent/room, whether they are seedlings, in vegetation, or flowering.
Emerald: Are there any mistakes to avoid when planting autos?
JP: Yes, minimize stress for best results. Unlike photoperiod plants, autos can’t recover as quickly because their biological clock keeps ticking. Some growers use low-stress technique, topping, or fimming. But for most, these techniques cause more problems than benefits. Always plant autos directly in their final pot to avoid delays in growth.
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