How To Grow Weed On A Windowsill: Key Considerations

Not everyone has a good outdoor space to grow cannabis, nor is willing to invest in expensive indoor grow equipment. Meanwhile, most people will have at least one windowsill in their apartment. And while it’s far from optimal, it is possible to grow a healthy cannabis plant on a windowsill. Here’s how.

STEP 1: SET YOUR EXPECTATIONS RIGHT

Cannabis is a hardy plant that can grow in a variety of different conditions, even on a windowsill. However, it’s really important you understand that your plant will only produce a small amount of bud in these conditions.

Don’t get disillusioned by the pictures you see posted by professional growers and even seedbanks—a cannabis plant grown on a windowsill won’t look like your average bush. Instead, they’ll likely produce little more than a few grams of bud, the quality of which will depend on how much light, nutrients, and love you’re able to give your plant.

STEP 2: PICKING THE RIGHT SPOT

Cannabis plants need a lot of light. If you’re going to grow on a windowsill, make sure to choose a window that gets as much direct sunlight as possible. Cannabis also likes warm temperatures of 18–30°C and humidity levels of 40–70%. Wherever possible, try to meet those conditions either artificially using air conditioning and humidifiers, or naturally by growing at a suitable time of year.

Remember, in nature, cannabis grows from spring (when seeds germinate) till the beginning of fall or winter when the plants naturally wither and die.

STEP 3: PICK THE RIGHT STRAIN

Picking the right strain of cannabis is always important when growing cannabis, but if you’re growing on a windowsill, using the right genetics becomes paramount.

First and foremost, you’ll want to use an autoflowering cannabis variety when growing on a windowsill. Unlike photoperiodic strains, autoflowers do not flower based on a changing light cycle. Instead, they start flowering automatically once they reach a certain age. This is really important when growing on a windowsill, as you won’t have enough control over your lighting to force a photoperiodic strain to flower.

Secondly, you’ll want to grow strains that are extra-hardy and don’t require a lot of space. Stay away from growing tall sativas as they require far too much room to grow properly.

STEP 4: START YOUR SEEDLING

Once you’ve decided on a strain and got your seeds, you’ll want to germinate them. To do this, place the seeds between a few sheets of moist paper towel and keep them between two plates in a dark cupboard. They should start to sprout within a few days, at which stage you’ll want to plant them in soil.

For seedlings, you can just use a clear plastic cup as a pot, which will also allow you to keep a good eye on the plant's roots as they grow. Make sure to puncture some small holes in the bottom of the cup for drainage, and fill it with regular moist soil. Make a roughly 1cm-deep hole, put your seed inside, and cover it. Now, place your seedling on your windowsill. It should sprout out of the soil within a few days.

STEP 5: CARE FOR YOUR SEEDLING

Cannabis seedlings are very fragile. They like warm, humid environments, so it's a good idea to cover your seedling with a plastic bag and spray some water inside every few days to keep things humid. Just be careful not to overdo this as too much moisture can make for a breeding ground of bacteria and fungi.

Leave your seedling to grow until it has developed a few nodes and at least one leaf with a full number of fingers (this will range between 7–13 fingers, depending on the strain). Once you see its roots growing from the bottom or side of the plastic cup, it’ll be ready to move into a bigger pot.

STEP 6: PREPARE YOUR POT AND SOIL

Soil is the best medium when growing on a windowsill. And the better the quality of your soil, the better the health of your plants and the bud they produce.

But before you even think about your soil, you’ll need a pot to hold your cannabis plant. Normally, cannabis growers use pots of anywhere from 10 to 40 litres in size, but those obviously won’t fit on a windowsill. Calculate your space and try to get your plant the biggest possible pot, keeping in mind that the more soil it has, the bigger it will grow. Also, remember to use a pot with plenty of drainage holes.

Once you’ve picked your pot, it’s time to prepare your soil. The easiest way to do this is to buy high-quality soil from your local gardening store and mix it with roughly 30% vermiculite. This will make for a well-draining soil, which is perfect for cannabis. As your plant grows, you can use fertilisers to help it reach its maximum potential.

If you want to stay away from fertilisers, you can take the time to prepare your own soil before you decide to plant. You’ll still start with store-bought soil, but over a period of months you’ll enrich that soil with all kinds of ingredients to create a nutrient-rich medium for your plants to grow in.

Start by mixing together 3 parts soil, 1 part vermiculite, and 1 part worm castings. Next, you’ll want to add in some greensand, dolomite lime pellets, and guano. The amount you use depends on the size of your pot. The package of each product should have dosage information, so make sure to calculate based on the amount of soil you’re using.

Once everything is mixed together, wet the entire mixture and let it sit for three days before putting in your seedling.

STEP 7: FEEDING YOUR PLANT

When feeding cannabis plants, you have two main options: store-bought or homemade nutrients, both of which have their pros and cons.

Store-bought nutrients can be exactly calculated, so you know exactly what you're giving your plants. They also come in different solutions specialised for vegetative growth and flowering. However, many of these nutrients are synthetic and need to be washed out of your soil in the weeks before harvest to ensure they don’t leave traces of chemicals in your final product. When not used properly, these nutrients can also cause nutrient burn in your plants, which can be detrimental if not handled properly.

Homemade nutrients, on the other hand, are natural, and can be made by brewing food scraps (like vegetable cuttings, coffee grounds, and used tea leaves) into a kind of “tea” that you can then use to water your plants. These teas don’t need to be washed from your soil before harvest and can give your plants a broader spectrum of nutrients than just a regular NPK solution. The downside here is that you won't know exactly what concentrations of which nutrients your plants are getting. These teas also take some time to prepare.

A NOTE ON PRUNING/TRIMMING

Cannabis growers regularly use pruning or trimming to force their plants to grow in a specific way and produce more buds. When growing on a windowsill, we only recommend very light trimming or pruning. Remember, you’ll be working with small automatic plants that generally won’t have time to fully recover from any high-stress training before they go into flowering.

PICKING THE RIGHT STRAIN TO GROW ON YOUR WINDOWSILL

As we mentioned earlier, it's very important you choose the right genetics when trying to grow cannabis on a windowsill. Below is a brief list of some of our favourite autoflowering strains that’ll hold up well in these conditions.

LITTLE DWARF AUTOFLOWERING

Little Dwarf Autoflowering, as the name suggests, is a very small cannabis strain perfectly suited for growing in tight spaces like a windowsill. As a blend between Skunk and ruderalis, this strain is super-hardy, yet still capable of producing some very aromatic bud. Little Dwarf Autoflowering typically takes 7–9 weeks to move from seed to harvest and produces 40–80g/plant, depending on its environment and the skill of the grower.

POWER PLANT XL AUTOFLOWERING

This little indica-dominant powerhouse is an autoflowering alternative to the original Power Plant XL. This strain can produce a really great harvest, even in colder conditions, and has slightly less dense buds, meaning it’s less susceptible to bud rot and other fungi. It will be ready in around 8 weeks from seed to harvest, at which point it’ll reward you with some delicious bud containing up to 15% THC.

GREEN AK XL AUTOFLOWERING

AK-47 is an epic strain that’s renowned all across the world. Our Green AK XL Autoflowering combines these amazing genetics with ruderalis, making for an awesome auto that can produce up to 100–150g of top-shelf weed per plant. Best of all, these plants hardly grow any taller than 100cm, making them perfect for growing on a windowsill.