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When Plants Don’t Flower

What to Do When Your Plants Won’t Flower

Like all plants, marijuana plants use light to fuel growth. During the seedling and vegetative stages, the energy produced by photosynthesis goes to building sturdy stalks, stems, branches, and large leaves. Once plants enter the flowering stage, that energy gets redirected to producing what every marijuana grower wants: large, juicy buds.

Light Use During the Vegetative and Flowering Stages

Plants perform photosynthesis during all life stages. This process, which takes place in the chloroplasts, uses the energy from the sun to create sugar out of air and water. As a general rule, the more light plants get, the more efficiently they can photosynthesize. However, marijuana plants did not evolve to tolerate 24/7 light. Instead, they use queues like light duration and intensity to determine when to move from the vegetative stage to the flowering stage.

Light Spectrum

During the vegetative stage, plants need access to more blue spectrum light. Blue light fuels chlorophyll production, which drives photosynthesis. Marijuana plants, like those from gorilla glue seed, use more of it while they’re in the vegetative stage to ensure that they can grow strong, healthy leaves, stems, and stalks.

In the flowering stage, marijuana plants use more red spectrum light. This makes sense given that cannabis seeds evolved to grow, flower, and then put out more seeds in the fall. Red light mimics the sun’s light spectrum when it gets lower in the sky at the end of the growing season.Some growers simply use red/blue spectrum LEDs throughout both the vegetative and flowering stages. Others switch from MH to HPS lights when they induce flowering. Either solution is fine.

Those working on a budget can also use fluorescent lighting, but there are a few unique concerns they can’t afford to overlook. First, it’s important to switch from cool lights to warm lamps when the plants reach the flowering stage. Second, growers need to ensure that their plants don’t get too close to the lights.

Light Intensity

Outdoor growers don’t have to worry about light intensity. They live with whatever the sun provides. Indoor growers have complete control over lighting, which means their plants will get 100% of the light they need to thrive, even on rainy days, but it also means they need to tailor their light intensity to the plant’s needs.

As a general rule, sativas (like blue dream seeds) require more intense light than indicas (like (any kush seeds). This makes sense given that sativas developed in tropical climates, while indicas are generally considered temperate strains. The sun is closer to the earth in the tropics and the temperatures are hotter, so sativa plants evolved long, skinny leaves to optimize the balance between photosynthesis and transpiration. Sativas need around 60 watts per square foot of light, while indicas can thrive with only 40 watts.

Light Duration

Marijuana plants also evolved to flower when the days start getting shorter. Growers using indoor weed seeds can mimic this environmental condition by switching their light schedules over from the recommended light schedule for the vegetative phase, which is 18 hours of light and 6 hours of darkness, to a 50/50 split.

Switching the plants over to a 12/12 lighting schedule is the easiest way to induce flowering. As long as the plants have spent sufficient time in the vegetative stage, they should take this as a cue that it’s time to start putting their energy toward producing buds.

In the wild, they would be doing so to reproduce before the end of their life cycle, since these annual plants can’t survive past mid-fall. Of course, growers don’t want their sour diesel

plants to reproduce, but they can still take advantage of this natural tendency. If switching the plants over to a 12/12 lighting schedule does not induce flowering within five days, there might be something wrong.

Common Problems and Solutions

There are three common problems that cause marijuana plants not to flower on time, even when buying the most premium seeds. Growers shouldn’t panic immediately if their plants don’t start producing bud within a few days, but it’s worth checking to make sure they’re not committing errors like giving their plants insufficient time in veg, allowing light to leak into their grow rooms, or disrupting the plants’ dark cycles.

Insufficient Time in Veg

The first thing to consider is the strain of marijuana. Some strains, like purple haze, require more time in veg than others. More specifically, indicas and indica-dominant hybrids typically flower earlier than sativas. Indicas will usually flower after between 45 and 65 days in veg. Sativa-dominant strains need to spend between 60 and 90 days in the vegetative stage before growers of marijuana seeds can successfully induce flowering.

Light Leaks

If there are light leaks in the grow room, switching the lighting schedule over to 12/12 won’t accomplish much. Growers just need to find the leaks and patch them up. They can then expect their plants to start flowering within four or five days.

Interruptions to the Dark Cycle

Brief interruptions to the dark cycle won’t usually have too much of an impact on marijuana plants from i49 seeds, but substantial interruptions can cause plants to remain in the vegetative stage. It can even cause plants (from cement shoes seeds or mango kush seeds) in the early stages of flowering to revert to vegetative growth.

It’s common for home growers to have problems with dark cycle interruptions. If there’s no way to avoid going into the grow room during the dark cycle, install green lights and use them when the plants are supposed to be kept in darkness. Plants can’t absorb green light, so it won’t affect them like red or blue spectrum light would.

When plants have been exposed to too much light, growers should switch them back to an optimal lighting schedule as soon as possible. Expect the buds to take a little longer to reach maturity.

If the lights have been left off for a day or two, it doesn’t usually cause too much trouble. The buds might be ripening faster than usual, but growers can just go back to a normal 12/12 lighting schedule and harvest them on roughly the same timeline.

Irregular changes to the lighting schedule can be more detrimental. If the plants aren’t producing any buds at all, growers are in luck. They can just change back to a normal lighting schedule and wait a few extra days for buds to start developing. If the buds have already started to develop, they may exhibit irregular growth. Plants exposed to irregular lighting for prolonged periods are also more prone to developing hermaphroditism, so keep an eye out for pollen sacs and bananas. This is seen in white widows strain seeds as well as any other hybrid marijuana seeds for sale.

The best way to avoid disruptions to plants’ dark cycles is to purchase lights that can be set to a timer. Set it to go on and off every 12 hours, then just check the lights periodically to make sure they’re coming back on in time.

A Simple Solution

Growers who are concerned about their abilities to provide consistent lighting according to their plants’ needs can plant autoflower seeds. These seeds are cross-bred with the lesser-known Cannabis ruderalis subspecies, which transitions from veg to flower with age instead of the light cycle. Strains bred with these hardy plants are smaller than their photoperiod relatives, but they produce crops much faster, and there’s no need to worry about light deprivation.

A Note About Outdoor Grows

It’s common for growers to assume that as long as they cultivate outdoor gardens instead of growing indoor seeds, they don’t have to worry about lighting schedules and their plants will flower on-time, every time. Unfortunately, this is not always the case.

Growers who want to cultivate photoperiod strains of marijuana using regular seeds in climates that have short growing seasons may need to use light deprivation to induce flowering. In places with short growing seasons, the first frost comes much sooner than it does in warmer climates. If growing outdoor seeds, growers must allow their plants to enter maturity and start flowering on their own natural schedules, they may wind up having to choose between harvesting early and risking potentially severe crop losses.

The solution to this problem is simple. Build a hoop house and black-box the plants. Hoop houses are small greenhouses, often built out of PVC pipe. They can be covered in clear plastic during the day to extend the growing season slightly, but they can also support opaque coverings. This allows growers to induce flowering on their own timeframe, provided their plants have spent a sufficient amount of time in veg.

Outdoor growers in northern climates can also plant auto-flowering varieties. This ensures that the plants will produce a good crop from your medical marijuana seeds within a short time frame, removing the stress of worrying about the first frost dates.

The Bottom Line

More often than not, novice growers worry too much about when their plants should start flowering. There’s no need to panic if they don’t produce buds within a few days of switching over to a 12/12 lighting schedule. If it’s been a week or longer, check for the common problems listed above. If growers are certain that their grow rooms are completely dark for 12 hours a day, their plants are receiving sufficient light, and they’ve spent enough time in veg, it’s time for them to consider the possibility that they’re not growing marijuana plants. Next time when asking yourself how to buy marijuana seeds, consider buying weed seeds from a more reputable marijuana seed bank. is the most well-equipped cannabis seed bank USA growers are using in the 21st century.