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Hydroponics Cannabis Growing Guide

Hydroponics is a method of cultivating plants, specifically cannabis in this case, in a solution of water and nutrients.

Contents:

As the name may suggest, hydroponics is a soilless method of growing cannabis using water as the primary medium. Within a hydroponic setup, cannabis plants are grown in buckets or baskets filled with an inert growing medium, and are suspended over a tank full of water. The water is filled with all of the nutrients plants need to survive and thrive, and air stones are used to aerate the tank. This basic model manifests in many different forms and systems, with different growers preferring different setups. There are many advantages to hydroponic cultivation, all of which will be covered in this article. But first, let’s delve into the history of this fascinating art form.

THE HISTORY OF HYDROPONICS

Hydroponic cultivation might initially seem like the result of modern advances in technology. But this couldn’t be further from the truth. The origins of growing plants in water goes back thousands of years into human history. The famous Hanging Gardens of Babylon, created in 600 BCE, are theorised to have utilised hydroponic principles. The region located next to the Euphrates was naturally dry and arid. It’s believed the crops of the garden were nurtured using a trickle-system starting at the river.

Moving closer in time to the 10th and 11th centuries, the Aztec civilisation was also known to utilise hydroponics to provide sustenance to their society. After being forced from their land via conflict, these people settled at Lake Tenochtitlan. They proceeded to build floating rafts topped with soil, allowing crops to grow through the tap layer and spread their roots into the waters below.

More recent, but still distant, examples of hydroponic growing involve the English scientist John Woodward in 1699. His work involved cultivating spearmint plants in water. He found that the plant species grew faster within a water source mixed with soil.

The history of hydroponics has shown how effective this method can be in many different settings and scenarios, with cannabis cultivation being no exception. Let’s explore the advantages of this interesting method, and how to apply it to growing great weed.

THE ADVANTAGES OF HYDROPONIC GROWING

If you talk to a grower who has experience with hydroponic growing, one of the first things they’ll probably tell you is that their hydroponic plants grow much, much faster than those in soil. This is a prime advantage of this method of cultivation—hydroponic plants usually grow 30–50% faster and often provide larger yields. A large reason for this is that nutrients within a hydroponic system are much more readily available to plants. The nutrients are suspended in water and enter directly into the root system as there is no soil to navigate through. In contrast, plants growing in soil must search through the medium in order to uptake nutrients from below. Easy access to nutrients allows plants to preserve energy, which is then diverted to growth efforts instead.

MATERIALS NEEDED TO MAKE A DIY HYDROPONIC SYSTEM

If you go the DIY route, check out the brief guide below. The list covers all of the equipment you need to construct a basic indoor setup. Simply find the product that suits you for each listed item. Buying your gear separately allows you to invest more heavily into important items such as lighting while reducing the cost in other areas.

Here’s what you’ll need:

a) Lighting (LED or HPS)

b) Lighting hangers

d) Hydroponic reservoir and tray

e) Airstone and pump

f) Growing medium (e.g. coco coir)

g) Net mesh planting pots

i) Ventilation fan and ducting tubes

j) Carbon filter

k) Oscillating fan

l) Hydroponic nutrients

m) pH and PPM meters

THE COST OF GROWING WITH HYDROPONICS

When thinking about hydroponics, you might picture a high-tech setup: automated switches, flashing lights, ticking timers. However, the cost of a hydroponic system all depends on how much money you’re willing to splash. They range from a simple plastic bucket all the way to self-draining and flooding systems. To save time, invest in a cheap hydroponic starter kit. These include all of the materials you need to get from seed to harvest. You can purchase one for around £200 (€235).

1. CHOOSE A GROWING MEDIUM TO GET THINGS STARTED

Now that we have covered the history and benefits of hydroponic growing, it’s time to get things started. To begin, you’ll need to select a growing medium—a substance that will hold in place the intersection of the stem and roots. From this location, the roots will grow down into the water in search of nutrients. The inert medium also allows good air access to the top of the roots. There is a huge list of different media used by cultivators, with those below being the most common. Each medium has its own unique benefits, and some work better with different systems. It’s all about experimentation when starting out to see which works best for you.

  • CLAY PEBBLES

As one of the most popular options, clay pebbles are excellent at aerating root systems. Clay pebbles sometimes require that growers alter the pH in order to provide an optimal growing environment, however, pre-altered pebbles can be purchased. You’ll need to place clay pebbles into a plastic hydroponic basket that has spaces for roots to grow through.

As one of the most popular options, clay pebbles are excellent at aerating root systems. Clay pebbles sometimes require that growers alter the pH in order to provide an optimal growing environment, however, pre-altered pebbles can be purchased. You’ll need to place clay pebbles into a plastic hydroponic basket that has spaces for roots to grow through.

  • ROCKWOOL

Rockwool is another popular choice, and is a substance created using volcanic rocks with a wool texture, hence the name. Rockwool has a tremendous capacity to retain water, which allows for good hydration of the upper root system. Rockwool can be placed within a hydroponic basket, but can also be lodged directly into the top of a bucket or tank lid without.

Rockwool is another popular choice, and is a substance created using volcanic rocks with a wool texture, hence the name. Rockwool has a tremendous capacity to retain water, which allows for good hydration of the upper root system. Rockwool can be placed within a hydroponic basket, but can also be lodged directly into the top of a bucket or tank lid without.

  • PERLITE

Perlite is a volcanic glass that expands when exposed to high temperatures. It’s often used in garden soils to provide aeration, which is exactly why it’s beneficial to use as a hydroponic growing medium for cannabis.

Perlite is a volcanic glass that expands when exposed to high temperatures. It’s often used in garden soils to provide aeration, which is exactly why it’s beneficial to use as a hydroponic growing medium for cannabis.

  • COCO COIR

Coco coir is a good sustainable option for a growing medium. As the fibre from coconuts, coco coir allows for good aeration and moisture retention. Coconut fibres are also known to protect roots from infection due to the presence of plant-stimulating hormones.

2. CHOOSE A HYDROPONIC GROWING SETUP FOR YOUR PLANTS TO THRIVE IN

Now that you’ve selected a growing medium, it’s time to choose which type of hydroponic setup to use. All systems are similar in that they utilise a nutrient-enriched water solution. However, setups can vary widely depending on factors such as water exposure and circulation. Most of the following systems can be purchased, but those with DIY skills could easily make them by using buckets, drills, pumps, and air stones.

DEEP WATER CULTURE

Deep water culture is a good place to start for beginners, and is likely the cheapest option. Plants are placed in buckets filled with a nutrient solution and an air pump provides a constant supply of oxygen.

EBB AND FLOW

An ebb and flow (also known as flood and drain) system features water that, well, ebbs and flows. These systems consist of several buckets suspended above a growing tray that features a water inlet and outlet. Both of these waterways are connected to an external tank that contains nutrients, an air stone to aerate the water supply, and a pump to move water into the growing tray. The roots in these systems are not continuously submerged within water. Instead, water periodically floods the growing tray with fresh oxygen and nutrient-enriched water. Once the pump cycle ends, all of the water drains back into the external tank.

This system allows for periodic feeding. The time when the growing tray is empty allows growers to easily tend to plant roots and harvest plants.

DRIP SYSTEM

A drip system in hydroponics is very similar to a drip irrigation system when growing in soil. This system consists of a large tray filled with growing medium, such as clay pebbles. Plants are placed directly into the medium, and each has its own drip pipe nearby. An external water tank with a pump and air stones constantly supplies a drip feed of water over each plant. The roots of these plants are constantly exposed to air, and the excess water drips down the medium and back into the external tank.

NUTRIENT FILM TECHNIQUE

If deep water culture is the equivalent of growing cannabis plants in a pond, then the nutrient film technique is the equivalent of growing weed over a river. This system involves placing plants into a tube that is angled, so water can enter at one side and exit at the other via gravity. The roots grow down into the tube, where they are exposed to the flowing water. The water enters from a tank with an air stone and pump, and returns back once the cycle is complete.

WICK SYSTEM

A wick system is a basic hydroponic setup that uses a growing tray similar to the drip system filled with clay pebbles. Under the tray is a tank of water, from which several wicks exit and enter the growing medium. Water travels up the wicks and passively hydrates the medium. No pump is required for this system.

AEROPONICS

Aeroponics is perhaps the most futuristic version of hydroponic growing, and uses misted water dispersed through the air to optimise aeration and hydration. Plants are placed into the top of a large tank of water filling the bottom 25%. Under the water is a pump that sends water into misters underneath the root systems. This fine mist constantly soaks the roots, allowing plants to receive massive quantities of air and water simultaneously.

3. PREPARE YOUR SYSTEM TO ENSURE A SUCCESSFUL GROW

After choosing your system, it’s important to prepare it well to prevent any detrimental situations. The damp and dark nature of water tanks is an ideal growing environment for a host of pathogens. Before running your system, you will need to sterilise your equipment to minimise the chances of contamination. Wipe down all of your buckets, trays, pipes, and tanks with rubbing alcohol, hot water, and peroxide. Once your system is sterilised, begin following the instructions to set it up correctly.

YOU’LL NEED TO MAINTAIN YOUR SYSTEM REGULARLY

Every hydroponic system requires frequent maintenance to provide an optimal growing environment. Below are all of the major factors you need to be aware of.

A) ALWAYS MONITOR PH

You’ll need to constantly test the pH of the water to ensure an optimal growing environment. Nutrients are more available to plants when the environment is slightly more acidic. Therefore, a pH of 5.5–5.8 is required. Use a pH testing kit to take regular readings, and be sure to change the solution weekly to maintain this range. During flowering, a pH of 6 is preferred.

B) TRY TO KEEP YOUR WATER TEMPERATURE AT AROUND 20°C

Hydroponic cannabis has an ideal temperature of 20°C. This factor can be monitored using a water thermometer and altered using a water heater if the temperatures are too low.

C) PROVIDE THE CORRECT QUANTITY OF NUTRIENTS

Hydroponic plants require the same nutrients as their soil-based counterparts. The easiest way to go about feeding your plants is by purchasing hydroponic nutrient solutions that contain all of the required substances for both the vegetation and blooming periods. Products will also describe how often to add nutrients back into your system and how much dilution is required.

D) KEEP THINGS CLEAN TO AVOID CONTAMINATION

Both growing trays and tanks require emptying and cleaning around every two weeks. This process will keep the roots of your plants safe against invading pathogens and diseases. Repeat the same process mentioned above when initially preparing your system.

E) SELECTING A STRAIN FOR HYDROPONIC GROWING

Strain selection is an important factor of hydroponic growing. Plants grown within these systems are free to uptake nutrients extremely fast, which often results in explosive and rapid growth. For this reason, selecting a large, towering sativa variety won’t be your best choice, especially if your system resides within an indoor grow tent.

Smaller and more compact strains are ideal for indoor hydroponic systems. Beginning with a smaller strain is advantageous for several reasons. For one, it will let you cultivate several plants within a smaller space, allowing for more diversity and potentially bigger yields. Additionally, if your plants do go through a growth spurt, you’ll have room to deal with such sudden surges in height.

Below are two strains that we recommend for hydroponic growing.

WHITE WIDOW

White Widow is a perfectly balanced hybrid strain that features 50% indica genetics and 50% sativa genetics. She was created using parent strain White Widow S1, and provides a well-balanced high that stimulates and excites the mind whilst relaxing and stoning the body. A THC level of 19% ensures a powerful psychoactive experience that lasts several hours. These flowers contain a terpene profile that emanates grounding tastes and smells of earth and pine.

White Widow will reach a height of 60–100cm when grown indoors, making her an ideal candidate for the spatial demands of a hydroponic growing operation. Expect good yields of 450–500g/m² after a flowering period of 8–9 weeks.

Hydroponics is a method of cultivating plants, specifically cannabis in this case, in a solution of water and nutrients.

How Often Do I Water Indoor Marijuana Plants?

If you’re growing marijuana in soil or another growing medium like coco coir, you will have to hand-water your plants. Watering is an important part of growing cannabis indoors, and knowing how to water your plants will save you a lot of frustration!

How often do you give your cannabis water?

Well, you will want to water your marijuana whenever the top of the soil or growing medium starts to feel dry. I like to water when the medium feel dry up to my first knuckle, or about an inch.

  • Soil – Water plants when the soil feels dry up to your first knuckle (or if the pot feels light).
  • Coco Coir – Aim to water plants every 1-2 days. If coco is staying wet for 3+ days, try giving less water at a time until plants get bigger and start drinking more. Don’t wait for your coco coir to dry out, but don’t water if the top inch feels “wet”. If the container feels light, it’s definitely time to water!

How to water cannabis properly (when using a well-draining potting mixture with liquid nutrients)…

In soil, wait until the topsoil feels dry about an inch deep (up to your first knuckle – just use your finger to poke a hole in the soil and see if it feels dry).

In coco coir, you want to water every 1-2 days if possible and adjust the amount of water you give accordingly. The top inch doesn’t need to completely dry out between waterings.

If you’re regularly adding nutrients in the water, give enough water each time that you get 10-20% extra runoff water drain out the bottom of your pot. This prevents a buildup in the potting mixture because otherwise, you are continuously adding more nutrients to the system.

Go back to step 1. Note: If water takes a long time to come out the bottom, or if pots take longer than 5 days to dry out before the next watering, you may actually have a problem with drainage (more info below) or need to give less water at a time. If your plants are very small compared to the container they’re in, give water more sparingly until plants get bigger.

Growing in Super Soil?

  • If you’re growing in super soil or another heavily amended potting mix, you may not need to add extra nutrients to the water because your plants can get all their nutrients directly from the soil.
  • Any time you’re not adding extra nutrients in the water, you want to avoid getting runoff water because it will carry away some of the nutrients in the soil.
  • Watering until you get runoff is important when using liquid nutrients because it helps prevent nutrient build up, but with super soil try to give just enough water that you wet the entire medium but don’t get extra water coming out the bottom.

Some growers swear by the “lift the pot” method to decide when to water your plants (basically wait until your pot feels “light” since the plants have used up all the water). It’s up to you to decide what’s easier for you.

I usually water my cannabis with a 1-gallon water jug for small grows, or 5-gallon jugs for larger ones. Runoff water is collected in the trays and after a few minutes I suck it all up with a small wet vac .

How to Provide the Water

When I first started growing, I gave my plants water using a watering can. A watering can works great, but it’s hard to water a bunch of plants with one watering can because you have to keep filling it up.

An old-fashioned watering can will get the job done, but they typically don’t hold a lot of water at a time, which is inconvenient if you’re growing a lot of plants

I personally like using a Battery Operated Liquid Transfer Pump to water the plants. You can pump water from a bigger container to your plants. This is a 3-gallon water container from Wal-Mart, and the pump just reaches the bottom.

My grow tent is 2 feet deep and this reaches the plants in the back. However, I don’t think the tube is long enough to reach the back if your space is deeper than that.

Some growers set up elaborate drip feeds to pump water if they have a lot of plants they can’t easily reach, both homemade or pre-made.

Let us know if there’s something we missed. Growers get creative!

How to Collect Runoff Water

It’s important to keep plants on saucers or trays so you can remove the runoff water. You can collect the saucers one by one and dump them out, but that also gets inconvenient with many plants.

It’s inconvenient to empty saucers one by one if you have a bunch of plants, but you don’t want to leave plants sitting in runoff water

If you put your plant on plastic trays, and then put the trays on a slight incline by putting something small underneath in the back, it will catch all the runoff water and cause it to drain to the front. The item in the back only needs to be about half an inch thick, for example a piece of plywood. However, if you can find something more water-resistant, like plastic, that’s even better.

These 1’x2′ plastic plant trays work well if they fit your space. You can fit four of them in a 2’x4′ grow tent (this is the grow tent I use) with up to two plants each as long as your plant containers are 11″ wide or smaller at the base.

Put trays on a slight incline by placing something underneath the tray in the back. This causes all the water to come to the front for easier collection. Each of these trays has a small plastic board (which we found around the house from something else) under the back. Anything that’s about half an inch high will do the trick. These particular trays accommodate plant containers up to 11″ wide at the base.

Not sure how to remove runoff water after watering your marijuana? Wet vacuums can be a great choice, especially if you already have one in the house. I didn’t have one, so I got Bucket Head attachment which can turn any standard 5-gallon bucket into a wet vac. You can buy one online but it’s $10-15 cheaper if you get it in person at a Home Depot. Another similar option is the Power Lid, though it’s also a bit pricey.

A downside to the Bucket Head is it’s a little loud, just like most wet vacs. Luckily you only need to use it for a few minutes after watering your plants!

Removing runoff water is a great start to make sure you are watering your cannabis plants perfectly, but it’s also important to…

Make Sure Pots Have Good Drainage

It’s very important to make sure that water can drain freely from the bottom of the pot, otherwise, the plant can get waterlogged and become overwatered (causing the plant to droop).

In addition to making sure the actual container has drainage (holes on the bottom, or some other way for extra water to escape), it’s also important to make sure your growing medium drains freely. If it takes several minutes for the water to come out the bottom of your pot when you water, it means that there isn’t enough drainage in the actual growing medium (it’s too dense, so water is having a hard time getting through).

How to improve the drainage of your growing medium

  • Never use dirt you find outside. Chances are it does not have the correct properties for vigorous cannabis growth.
  • Mix in extra perlite to loosen the soil and allow water to drain through more easily.
  • Bark or wood chips are not the best choice for growing cannabis plants, even though they’re sometimes recommended to improve drainage in soil for some types of plants. On that note, avoid using soil that contains bark or wood chips. What makes soil good or bad for growing cannabis?
  • Use Smart pots – these fabric pots help get oxygen to your roots (which gives you faster growth) and this type of pot makes it harder to overwater your plants. A cannabis plant growing in a tan fabric smart pot is pictured to the right.

This is an example of great soil for growing for cannabis – rich, composted, and well-draining

Composted super soil lets you grow organic marijuana without any extra fertilizers or nutrients

Watering Too Often? Barely at All?

In the beginning of your grow, you will likely be watering your marijuana plants every couple of days. Watering every 2-3 days is optimal for a young plant. If it’s taking too long for your plant to dry out, you may need to give less water at a time until the plant is growing faster.

If you feel like you are watering your plants too often, you may need to give more water at a time. You can also move plants into a bigger pot (which holds water for longer).

If plants take longer than 3-4 days to dry, make sure your potting mixture has good drainage and consider giving less water at a time

If plants are drying out in 1 day or less, try giving more water at a time or transplanting to a bigger pot

Speaking of pot size, it is generally best to start young cannabis plants in relatively small containers (like a solo cup with a few holes cut out of the bottom for drainage), and move plants into bigger containers as they get bigger. Starting in smaller containers makes it a lot harder to overwater your plants when they’re young, and makes it easier to flush plants and/or respond to problems if they occur.

That being said, you can plant your seeds right into their final container. Just be careful not to overwater your seedlings at first if they’re in a big container as they’re not drinking much water in the beginning.

If you started your plants in a solo cup, I’d recommend moving to a bigger pot once the plant is a week or two old, as soon as the leaves reach the edges of the solo cup.

10-20% Extra Runoff Every Time You Water (if you’re providing nutrients in the water)

Every time you water your plants, make sure that you provide enough water to get about 10-20% extra run-off out the bottom of the container, especially if you’re feeding additional nutrients in the water.

Sometimes soil and soilless growing mediums like coco coir start to collect natural salts from fertilizers that never get washed out.

These built-up salts can eventually cause nutrient problems, pH problems, and nutrient lock-out if they’re not removed on a regular basis.

Making sure you keep adding water until you get run-off is also a great way to make sure that your plants are draining properly.

Plus, this practice will immediately alert you to any drainage problems, (as mentioned earlier, cannabis likes well-draining soil) because you’ll be able to notice if the water takes a long time to come out the bottom, or doesn’t come out at all.

Different Nutrients for Different Stages of Life

First, make sure you’re using proper cannabis nutrients for your growing medium. They should be formulated for a plant like tomatoes, and they should have a different feeding schedule for the Vegetative (Grow) and Flowering (Bloom) stage.

If using nutrients on a regular basis by adding them to your water, it’s generally a good idea to give your cannabis plants nutrients every watering. This ensures the amount of nutrients in the plant root zone is kept relatively stable. If you notice the tips of leaves getting burnt from nutrient burn, it may mean you need to lower your overall strength of nutrients. Most nutrient recommendations on the side of the bottle are too strong for cannabis plants, and should be cut in half unless plants appear pale or lime green (which means they want higher levels of nutrients overall).

If Growing in Composted or Amended Soil, Give Just Enough Water That the Soil is Wet All the Way Through

When growing in composted and amended soil, the soil itself is made to slowly provide nutrients to your plant throughout its life. However, if you’re regularly watering until you get a significant amount of runoff, you’ll also be washing away some of your nutrients.

This is good when the plant is getting the nutrients directly in the water, to avoid unwanted buildup in the soil, but try to avoid a lot of extra runoff if you want your nutrients in the container to last until harvest.

Therefore, when growing in amended soil you should only water until you get just a drop or two of water runoff out the bottom. You want to ensure you gave enough water to reach the bottom of the pot without letting a significant amount of water run out the bottom.

Proper watering practices will greatly help reduce the amount of salt buildup and prevent nutrition problems from occurring.

If your cannabis plants shows signs of drooping, often the plant is getting too much or too little water, but not always. Drooping can be caused by….

  • Too much water at a time, or giving water too often
  • Not enough water at a time, or giving water too infrequently
  • Drooping can also occur in hot conditions, or when it’s very humid or dry because the plant isn’t able to move water properly through the plant.
  • Plants sometimes get droopy if they are given a lot of water after being allowed to dry out for too long, due to the stress of the water pressure quickly changing at the roots.
  • Drooping is almost always associated with something going on at the roots, but plants also tend to put their leaves down a bit right before the lights go off, as if they’re preparing to “sleep” for the night. That can sometimes be mistaken as drooping when its actually part of the plant’s natural rhythm.

In order to prevent over or under-watering, make sure you water thoroughly every time (don’t just water a tiny spot in the middle of the pot unless you plant is very small for the container). You should be getting 10-20% extra runoff water every time if you’re adding nutrients in the water. In soil, wait to water again until the top inch of the growing medium feels dry, up to your first knuckle or so. In coco coir, aim to water the plants every 1-3 days if possible, and don’t let the top completely dry out between waterings.

Underwatered Marijuana Plants

  • Wilting is the first sign of underwaterd marijuana plants
  • Leaves are limp and lifeless, they may seem dry or even “crispy”
  • Will eventually lead to plant death if not corrected

Overwatered Marijuana Plants

  • Drooping / Curling is the first sign of overwaterd marijuana plants
  • Leaves are firm and curled down all the way from the stem to the leaf
  • Will eventually lead to leaf yellowing and other signs of nutrient problems if not corrected

If your plant is experiencing “the claw” and not just normal drooping (like the ends of leaves are just pointing down like talons, then you may actually have a nitrogen toxicity (too much nitrogen).

Nitrogen Toxicity (“The Claw,” tips bent down, dark leaves)
Learn more about Nitrogen Toxicity

Learn everything you need to know about watering your cannabis plants. No more guessing or worrying!