So you’ve read Growing Your Own Medicine and you’re keen to get started? Great – but don’t hang about! Cannabis is very fast growing, but even the quickest strains (you can search for quick growing types in any good online seed shop) will take over two months to go from seed to harvest-ready plant.

Tip: if your need is urgent then perhaps buying an ounce of ready-to-consume grass from some friendly local smoker while you’re tending to your crops is a good idea.

You’ll need to allow for up to a week to germinate some seeds and get ready to be put into small inert propagation plugs, then up to a further week while the roots grow and start to push through the outsides of the plugs. From then you can put the plugs into larger cubes. Rockwool is a good medium for this; it’s inert, it holds water well, and roots can penetrate the material easily.

Once a well-rooted seedling gets going in an NFT system it soon starts growing quickly. I often find a month in the grow tent gets them to a good size. Don’t let them get too big before they start flowering, as they’re likely to grow anywhere from 50% to 100% taller while moving into their flowering stage!

And oh yes, you do 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 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. 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.

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.