If you’re going to grow your own cannabis – which I do recommend if you have the space – you need to be careful what varieties of cannabis seeds you get. First of all there are three main behavioural types: Regular, Feminized, and Autoflowering…

Regular, Feminized, and Autoflowering

Regular means the seeds may grow into male or female plants, and that means you’ll need to know how to spot male flowers ASAP so you can remove them before they pollinate the females. If that happens the potency of the plant drops as the female switches its energy into growing seeds.

Tip: avoid buying Regular seeds unless you’re confident about catching and removing males before any pollen is created.

Feminized means the seeds come from a plant that’s been bred to produce nothing but female-ready seeds. This isn’t 100% foolproof, as stress during a feminized plant’s life can cause it to produce male flowers, but this isn’t common.

With both regular and feminized plants, keeping them in a regime of 24 hours of light will keep them in the vegetative stage, growing but not flowering. To provoke flowering, set up a 24-hour timer for your LED units so they’re switched off roughly half the time. And DON’T peek in on them or allow any stray light to reach them during their ‘night’ or they’ll get confused and switch back to veg stage.

Autoflowering means the plant will automatically start flowering once it reaches a certain age. This makes things simpler – I strongly suggest you start with autoflowering varieties – but autoflowering plants tend to grow a little smaller than their feminized or regular counterparts. They will still want the same day/night lighting regime as regular or feminized, but autoflowering plants don’t require that to start before they begin flowering. This means you can wait until you see flowers before switching the lighting cycle.

Cannabinoids: THC, CBD and others

Next, THC and CBD ratios. THC is the cannabinoid that produces the psychoactive effect, so this is traditionally the thing that many people care about. CBD is not psychoactive and, as a result, is considered legal in extractions and can be found in commercial medical preparations in districts and countries where ‘normal’ cannabis is illegal. But for medical use it’s important to have what’s referred to as a ‘full spectrum’ range of cannabinoids; alongside THC there’s CBD in particular, plus many other lesser-known cannabinoid types. These (particularly THC and CBD) appear to work together, so full spectrum is considered better than pure (and almost universally legal) CBD-only preparations.

Plant varieties that have mostly THC will have strong psychoactive effects; music will sound better, ads on TV will seem ridiculous, and so on. Plant varieties that are CBD-dominant will have little THC, and as a result won’t produce much if any of the ‘stoner’ effects. Varieties that are relatively balanced will have some THC and will have some psychoactive effects but not as much as THC-dominant ones.

Different kinds of illnesses benefit most from different varieties of cannabis, but rather than worrying much about this the general idea is to use strains that don’t knock you right on your ass but that you can feel. For medical use, look for strains that have roughly similar levels of THC and CBD – but don’t get too concerned about this until you’ve tried a few grows.

Indica, Sativa, Ruderalis

Given how much interbreeding of strains there has been over the last few decades, it’s rare to find a pure ‘landrace’ strain of cannabis. Most will be either indica or sativa dominant but not 100% pure. This isn’t particularly important for most people, but it’s worth noting the different effects these two types can have. However, see the Harvest Time post for more on this, as this can be affected as much by how soon you harvest.

Sativa tends to produce a relatively buzzy, ‘up’ effect which can be invigorating but some can find also provokes feelings of edginess. These will grow taller and have thinner leaves than Indicas, and the height can be a problem if you’re working with a modest size of grow tent. If so, avoid particularly tall Sativa varieties.

Indica is more likely to produce a physical stone effect, often called ‘couch lock,’ that is extremely relaxing but gets in the way of actually doing stuff. Indica leaves are broader than Sativas, and they don’t tend to reach quite the same heights.

Ruderalis is a variety of cannabis that has adapted to grow in more northern climates such as the Russian steppes. This is where the autoflowering genes come from. These grow shorter even than Indicas, so they are normally not the dominant type of any cross. You’ll almost certainly not see a pure Ruderalis or even a Ruderalis-dominant cross; it’s much more likely to be just used to get reliable autoflowering genes.