Cannabis Flowering Problems: Why Plants Bloom Too Early or Too Late

Cannabis flowering problems, like plants that bloom too early, too late or only partly, usually come down to a handful of causes: old or weak genetics, stressed clones, unhealthy roots and not enough light. Problems in a grow can pop up without warning, and odd flowering is one that plenty of growers run into sooner or later.

The causes vary, and so do the symptoms: a whole crop can start flowering ahead of schedule, kick in way too late, or only part of the garden may be affected. Here are some of the most common reasons cannabis flowering goes sideways.

Old or low-quality seeds

Growers know that old seeds don't just take longer to sprout (if they germinate at all); plants grown from old seeds can also grow much more slowly at times.

And if you want a strong plant with healthy, vigorous growth from seed to harvest, genetics matter too. Some strains are simply better at this than others, so do your homework before you pick what to grow.

Stressed clones

Sometimes clones just don't develop good roots, and there are lots of possible reasons why. Either way, keep an eye on it, because it can hold back their growth. To prevent it, your best bet is to dip the base of the cutting in a bit of rooting hormone right after you take it.

You'll also want a growing environment that encourages root development. Check the growing medium: it should be moist (but not soaked) with a pH of around 6.0. Keep clones at about 22 °C (72 °F). If it's too cold, they may not root at all; if it's too hot, the roots will die.

Root health

If your plants' roots aren't getting enough oxygen, their metabolism can slow down. In some cases, a lack of oxygen can stop growth altogether. Typical culprits are overwatering and growing media that drain poorly.

So how do you avoid it? Use a light, airy, well-draining growing medium. If your soil doesn't drain well, mix in some perlite to open it up.

Also watch the temperature in the root zone: it should never run hotter or colder than the air around the plant.

And keep in mind that if you don't fix the drainage, mold, bacteria or physical root damage can seriously set your plants back. Always use opaque containers that keep light off the roots, because light hitting the roots is bad news too.

Not enough light

Light requirements vary from strain to strain, but light is one of the most crucial factors for any plant to grow well and show off the best traits of its genetics.

Not enough good-quality light can lead to slow growth. This happens most often indoors: if you suspect your plants are light-starved, try lowering your lamps closer to the canopy. If you're growing outdoors in containers, move your plants to a sunnier spot.

Why is my cannabis plant flowering too early?

Premature flowering can happen at any stage of your grow, and it can hit both unrooted and rooted clones. One of the easiest ways to prevent it comes down to moisture: keep the growing medium at the right moisture and fertility level before you put your clones in and from planting day on. That helps avoid water stress, wilting and flower buds forming on the emerging stems, which is exactly what you're trying to head off.

If you notice your plant jumping from vegetative growth into early flowering, you'll see stem growth slow down and the plant stay small. The stems stop putting out new leaves and nodes, which limits how long they get. And a whole crop that flowers too early won't have enough time to grow to a decent size.

Two ways premature flowering shows up

• First, premature flowering can hit the entire crop, with every plant blooming way ahead of schedule and blowing up your planned harvest date.
• Second, premature flowering can affect only some of your cannabis plants, and it often causes more trouble in some grows than in others. That can leave some plants ready way too early while the rest stay on schedule.

If your cannabis does flower prematurely, know that those early flowers start to wilt and die before the rest of the plant has even finished blooming. That leaves gaps in the canopy, with short stems topped by dead flowers.

So on top of harvesting earlier than planned, you'll get lower quality, it can mess with your plans and you may not get what you were after from that particular strain.