Opbox Grow Guide


Welcome to the Opbox grow guide. This guide will take you from seed to harvest, educating you on everything you need to know about growing in your Opbox. 

Controls & Settings

pH Balancing

Seeds & Germination

The first step to starting your grow is selecting the right seeds. Generally, there are three types of seeds you can buy. Standard, Feminized, and Autoflowering. What does this mean? We’ll break it down for you. 

Regular seeds are what we call mixed-sex, meaning they are comprised of both male and female seeds. Male plants won’t produce any 'consumable' buds, and they will pollinate any female plants nearby making them also non-consumable. For this reason, when growing with a batch of regular seeds, we want to ensure that no male plants survive long enough to release pollen. The only way to tell the sex of a seed is to grow it, flower it, and check what kind of 'body-parts' its producing. Males will grow little balls or pollen sacs, while females will grow pistils that look like little white hairs. If you see a plant starting to grow balls, you probably want to chop it down and throw it out immediately.

Now that you know what regular seeds are, you can probably guess what feminized seeds are. Yup, you got it, they’re seeds from a plant that has been modified to produce only female seeds. This is usually done by spraying them with non-toxic chemicals like colloidal silver. Feminized seeds are great because they reduce the need to distinguish and discard any male plants. These are the seeds we will be using for this tutorial series, and the ones we recommend.

The final seed category is autoflowering seeds. Autoflowering seeds do just as their name says - they automatically flower. Normally, you’d have to change the light schedule of the grow light from 18 on, 6 off,  to 12 on, 12 off in order to trigger flowering in a plant -effectively mimicking the change from summer to fall. But, with autoflowering there is no need for that. These seeds are great for beginners, or those who don’t want to worry about lighting, however they don’t allow as much control over the grow (since they flower themselves whenever they want). Autoflowering plants are generally grow smaller than regular seeds, and they cannot be “trained” as it will stunt their bud growth. 

Seeds are widely available across Canada, the US, and Europe. A simple Google search for “feminized seeds” should produce a number of reputable suppliers that will ship directly to you. A number of head shops and dispensaries will also carry seeds.

The first step of growing your plant is germination. This refers to the part where you turn your seed into a sprout. The first step in germination is to soak your seeds in water in order to ‘wake them up.’ It's as simple as filling a small glass with water, dropping your seed in, and taking it out after 12-24 hours have passed. Never leave your seeds in the water for more than 24 hours, as you risk ‘drowning’ them. 

You might have heard of some growers moving their seeds into wet paper towels after this step, but we prefer not to do that as we want to eliminate any risk of breaking the very fragile taproot once it sprouts. Instead, we will move the seed to a starter plug. To hydrate your starter plug, soak it in pH balanced water for 30 seconds. After your starter plug  has been hydrated, place the seed inside of it about ½ inch down and cover it with the excess grow medium around the hole so that it stays dark. Seeds prefer a warm environment, so if possible do your best to keep it out of the cold. 

That is it for germination! In 4-7 days you should see your seedling start to sprout up out of the medium. It’s important that your seedling gets light as soon as it breaks out of the medium, otherwise it will stretch itself out in search of a light source, in turn producing a weaker stem. Instructions on how to do this are in the following section.


When your seed sprouts and becomes a seedling, there are a few measures you’ll want to take to keep it alive. While a fresh seedling is in its earliest stages of life, it is the most fragile and sensitive. 

When you notice any signs of sprouting, start a new grow on your Opbox. You can do this by going to settings, then selecting the settings icon (more settings), and pressing ‘Start New Grow.” Your seedling will now have light to grow towards and it can anchor its taproot (its very first root) into the rockwool cube it was started in. Forgetting to start a grow on the Opbox may result in an overextended stem from extending towards an external light source. A long stem is usually weak, so an ideal one is short and stocky.

A seedling needs to be taken special care of. Since it hasn't fully established a root system, it will need extra humidity so that it can absorb water through its leaves. To achieve this, keep your seedling covered with the Opbox’s humidity dome. This will help prevent the environment from drying out -something you want to avoid from happening at all costs. 

Filling your Opbox reservoir with a thin layer of water (1 cm full) is an additional measure that can be taken to ensure a moist and humid environment. You can do this if your starter plug is drying out on you too often (more than a few times a day). The bubbler will help humidify the air, so ensure that it is turned on. If not, you can turn it on in the additional settings where you started a new grow. This may result in uneven root growth, so only do so if it is necessary. 

On top of keeping your seedling alive, your goal should be to have it grow roots through the rockwool starter plug (in all directions). Once your seedling has roots, it can absorb moisture through them and will not need as much care. You should expect this to happen over a week or so. When you see roots growing through, you can prop the humidity dome up for a day to let air in. Over a few days you can increase how exposed your plant is, eventually removing the humidity dome completely. If you notice your seedling starting to suffer, you’ve probably removed your humidity dome too quickly. 

We want the roots to expand throughout the whole starter plug before planting in soil or adding water to the system, so that the roots are encouraged to grow outwards rather than straight down. Once the roots have fully filled out the starter plug we can add pH balanced water to the hydroponic system or move the plant into a pot filled with soil. 

Whether growing in soil or hydroponics, it’s important to pH balance your water to a pH of 5.5 - 6.5. Learn more about how to pH balance your water in the video above.

If growing hydroponically, simply keep the starter plug in the net cup and add water to the system so that it is slightly below the bottom of the net cup. Make sure not to fill the reservoir past the air hole in the back of the reservoir or it may leak. From here, the roots will naturally grow down into the water. The clay balls that you added into the net cup will help with root aeration, prevent algae, and will support the plant. So, make sure the starter plug is secured into the balls and is not protruding above the top layer of balls.

If growing in soil, remove the starter plug from the net cup and add your soil to your pot (we recommend felt pots). The larger the pot, the larger the plant will grow, and the less frequently you will need to water. Since the Opbox is relatively small compared to the size that a plant can grow (think tree-sized plants growing outdoors), only a small pot (size #2 to #5) is needed. If you wish, the Opbox can fit 4 smaller pots for multiple plants, but this will require more maintenance. Once your pot is filled with soil, clear a hole in the middle that is large enough for the well-rooted starter plug and place it inside. Bury the starter plug and lower stem with the excess soil. 

Whether growing in soil or hydroponics, your plant is now in its new permanent home. 

Now that your plant has a root system, it’s time to start feeding it. Your plant absorbs nutrients through its roots, and giving it the correct amount will contribute to around 10% of its growth. In the next section you will learn how to feed your plant.

Vegetative Stage & Training

For the next few weeks of your plant's life, it will be in what’s called the ‘vegetative’ stage. This stage is determined by the plant’s light schedule, which will be on for 18 hours and off for 6 hours of the day. This effectively mimics the summer months of the year where the sun rises early and sets late. During this stage the plant will grow its leaves, branches, and stems. Our primary goal during this stage of growth is to encourage the plant to produce as many strong branches as possible, which will eventually each turn into a bud. We call the bud sites at the end of these branches ‘nodes.’

In order to encourage this type of growth, we will utilize two tactics: topping and low stress training.

Topping is the act of cutting off the newest growth of a node on a plant. When the newest growth is cut off, the single branch that contains the node will split off into two new branches. Topping effectively turns one bud-side or node into two bud-sites or two nodes. 

Note that these methods are not mandatory and are only used to increase harvesting yields. Do not attempt these methods on an autoflowering plant as it will stunt their growth.

To top, simply grab a node, find the top, and pinch it off at the base using your fingernails. Make sure you wash your hands beforehand! Our video will give you a better idea on how to do this, so make sure to check it out. Within a few days you should see two new branches start to grow (in replacement of the single branch site that was removed.)

Low stress training, or LST for short, is the act of bending and tying down the plant to encourage growth sideways rather than upwards. When the branches grow sideways, they fill out more of the grow space and allow for more branches to get access to the light coming from above. To LST your plants, gently bend them sideways once or twice a day and you’ll see them start to grow outwards in the direction that you bend them, while the middle branches get more light. If you don’t want to bend them every day, you can tie them down or hold them with training clips that are available on our website (or Amazon if that’s easier!).

While in the vegtative stage, you should feed your plants once a week. This involves topping up the reservoir with fresh, pH balanced water. After topping up your reservoir, dissolve your Grow nutrients into a separate cup of warm water. The amount of nutrients to add can be found on the feeding schedule that came with your Opbox. The amount of scoops to add (large and small) are determined by the week of growth. For example, on the first week of growth you’ll dissolve 1 large and 1 small scoop of Grow nutrients into your warm water. Once the nutrient powder has dissolved, you can pour the nutrient solution into the Opbox reservoir. Feeding your plant is an important part of growing, so make sure to do this on the same day of each week!

If growing in soil, simply water when the top 2 inches of the soil is completely dry. You can test this by sticking your index finger in the soil. If you feel no moisture at the depth of your finger… time to water. Some soils contain enough nutrients to last months without supplementing, however some soils will need some sort of nutrient supplement. If you’re growing in soil that requires additional nutrients, you can follow the steps in the previous paragraph and add the nutrient solution to your weekly waters.

If growing in an Opbox, it is time to flower your plant when it is around 8 inches tall. This should be 4 weeks from when you first started to feed it nutrients. In the first two weeks of flowering, the plant will double in height (or sometimes even more). You do not want your plant to outgrow the Opbox, so make sure you’re not too late when you start your transition! If your plant is not yet tall enough to flower, continue feeding it the Late Grow phase (week 3) nutrients until it is large enough. If you’re growing an autoflowering plant, skip to the Early Bloom phase (week 5) when the plant shows early signs of flowering (preflowers, white pistil hairs). Autoflowering plants should maintain a light schedule of 18 on (at least), 6 off throughout the entire grow.

Learn how to transition into the flowering stage in the following section.

Flowering Stage

Your plant will now move to its final (and longest) stage of life, the ‘flowering’ stage. This stage is determined by the plant’s light schedule, which will be on for 12 hours and off for 12 hours of the day. This effectively mimics the change from summer months to early-mid fall when the sun sets earlier.

To start your transition, enter the sunlight settings in your Opbox and change your light schedule to 12 hours on, 12 hours off.

As mentioned earlier, the plant will double or even triple in size when switched into the flowering stage, so it is important to flower your plant while you still have plenty of space left in the Opbox.

During the first two weeks of flowering, the plant will require a significant amount of trimming. It is important to only trim your plant within the first two weeks of flowering, or else it may take energy away from the production of its buds.

Heavily trimming your plant might seem counterintuitive. “Why take away potential bud sites that could produce more buds?” Because when the plant focuses all of its energy on the main bud sites that are receiving the best light, the main buds will grow so much bigger that they will produce more than if you grew multiple, smaller buds.

You will want to cut off any lower leaves and bud sites/branches that aren’t getting direct exposure to light. 

Lastly, continue to feed your plant weekly. From now on you’ll be using the Bloom nutrients instead of the Grow nutrients.


Before you harvest your plant, it is important to flush it for a week prior. The Flush phase (week 12) of the plant involves removing all nutrients from the root area (as shown in the Feeding Schedule at the top of the page). Without any nutrients, the plant will think it is about to die and put all of its remaining energy towards producing as large of a flower as possible. Flushing is key to ensuring large and potent harvests.

If growing hydroponically, simply replace the nutrient solution in the reservoir with fresh, pH balanced water. If growing in soil, pour a substantial amount (2x the capacity of the pot) of fresh, pH balanced water into the pot and let the excess water drain out. 

Harvesting your plant at the correct time is important to ensuring the quality of the bud you produce. If you harvest too early, your plant won’t have grown to its full potential and you will have a smaller harvest. On top of that, your bud will produce less of a ‘high’ when consumed. On the contrary, if your buds mature for too long, you may produce a bud with more CBD (which some people prefer) even with low CBD genetics.

There are two ways to determine the best time to harvest your buds, one easy and one slightly more difficult. 

We’ll start with the slightly more difficult, but more precise method -looking at the trichomes. The trichomes look like microscopic droplets on the flower of your plant and on the leaves touching the flower. They sometimes make the flower or leaves look ‘fuzzy,’ although they aren’t to be confused with the much longer, larger pistils (hair-like matter) on the plant. In order to get a good look at the trichomes, a magnifying device, such as a jewelers loupe, must be used. For most of the early flowering stage the balls of the trichomes will appear clear under magnification. If the plant has over matured, the balls of the trichomes will appear white under magnification. The ideal time to harvest a plant is when the trichomes are a milky, translucent white, meaning they are halfway between clear and white. At this point your buds are at maximum size and maximum potency. 

The simpler, faster, but less precise method for determining when to harvest your buds is by looking at the pistils on your flowers. The pistils look like long hairs coming off of the buds of your plant, and in the earlier stages of flowering will appear white. As the plant matures, more and more of the pistils will start to turn dark orange/brown or amber. Your plant is ready to harvest when approximately 75% of the pistils have turned orange/brown or amber. If most of the pistils are still white, it is too early. If almost all of the pistils are orange/brown or amber, you have missed the ideal harvest time. 

There are many ways to harvest, trim, and dry your plants, but we will cover the one we feel to be the simplest. Find a comfortable place to do this, as this can sometimes take hours. Oh, and it’s going to dank. Some may even smell it from a block away (seriously!).

Before harvesting, you will need a bin for garbage, a tray for trim (usually we use a baking tray covered in tinfoil), your trimmers, and a pair of rubber gloves to keep the sticky resin off your hands.

Harvest your plant by cutting off large branches one by one until you are left with the main stem(s), which you can then cut off as well. The next step is to trim off all of the large fan leaves from each of the branches and discard them. You should now have branches with only buds and smaller leaves.

Any smaller leaves that have visible trichomes on them should be kept (put them on the trim tray you prepared), as the trichomes are what contain THC, and these leaves can be used to make thc infused butter and oil. Trim off the smaller leaves, being sure not to accidentally cut off a stem containing a bud.

The buds can now be manicured to make them look like the bud you’re probably used to seeing. Simply take your scissors/trimmers, hold them parallel to the bud, and cut off any leaves that are protruding from the bud. The trimmings produced from manicuring the buds should be kept along with the smaller leaves containing trichomes. You should now have buds on your branches that look like… well… buds. You’re ready to dry them!

Dry & Cure

There are a few ways you can dry your buds. If you have a drying rack, you can place them on the rack and set your Opbox to ‘Dry Mode’ (found in additional settings). If you haven’t got a drying rack, simply place them upside down (with the stems up) inside the dry, Opbox reservoir, leaning up against the walls. You should also set the Opbox to ‘Dry Mode’ for this method. They will smell, so keeping them inside of your Opbox with the door closed is a good idea. The buds should be dry after 3-5 days. You will know your buds are dry when you are able to snap off a smaller piece of the branch rather than have it bend and stay intact. When you’re able to do so, you’re ready to cure your buds.

Curing your buds is an extremely important step. It adds more moisture content and weight back to them making them sticky rather than dry. An uncured bud will be much harsher when smoked. 

To cure, simply cut the buds off of the stem they are on and place them inside of an airtight jar. Humidipacks that maintain humidity levels inside the jar can be used but are not mandatory. Keep the buds inside the jars for at least 2 weeks, opening them 1-2 times a day to allow fresh air in. After 2 weeks, your buds will be ready to smoke.

And that is it! You have successfully grown your very own cannabis, from seed to harvest. If you didn’t manage to succeed on your first few tries, don't worry! It took all of our growing experts many times to get it right. Luckily, the Opbox should make things much more simple, but don’t give up if it doesn't work out right away. Happy growing!