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What Do Marijuana Plants Need To Thrive?

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September 14, 2020
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Cultivating cannabis, considering all the supplies and equipment needed, may seem daunting. As many would later find out, that is not true. Sure, there is a learning curve, but there are only a handful of things that your plants need to thrive. Best of all, they are manageable.

What Do Marijuana Plants Need to Produce Potent Buds and High Yields?

In a nutshell, the six things that affect growth are growing medium, water, nutrients, light, temperature, and humidity.

The growing medium houses the plants, keeping them upright. It is also where the roots find and absorb moisture, nutrients, and oxygen. As you will later see, the water and nutritional needs of cannabis plants vary across different growth stages. To keep them in top condition, ensuring they receive the right amounts as they grow are things you should do.

Meanwhile, light, temperature, and humidity constitute the growing environment. For outdoor cultivation, make do with what nature provides. As for indoors, apart from setting up an artificial lighting system, you should follow a strict light schedule suitable for the growth phase. On top of that, you also have to monitor and manage heat and moisture levels, ensuring that they fall within the optimal range.

1. Growing Medium

The first thing that cannabis plants need is a space to grow in – otherwise known as a growing medium. It should have room enough to facilitate maximum root growth and expansion while physically supporting the plants. More than that, it stores the moisture, nutrients, and oxygen that the plants need to survive.

In general, there are two types of growing media you could use for cannabis plants – soil and soilless.

Soil

Soil offers a traditional way of growing marijuana plants. Ideally, the chosen soil should have optimal texture, water retention, and drainage – which ensures that it can hold the right amount of water, nutrients, and oxygen. And, it should also teem with organic matter to boost the soil microbial populations. In most cases, you would have to amend the mix to achieve these qualities.

Advantages of using soil:

  • Acts as a foundation, anchorage, and structural support
  • Promotes gas exchange and keeps the root zone well-oxygenated
  • Keeps moisture and nutrients
  • Houses millions of beneficial microorganisms
  • Insulates the root zone and shields it against damaging elements

Soilless

You can use this versatile type of substrate for both pot-based and hydroponic systems. There are several choices, each with varying properties and composition. Among the most popular ones are:

  • Coco coir
  • Perlite
  • Vermiculite
  • Clay pebbles
  • Rockwool

These mediums are clean, porous, and feature a balanced air to water ratio, among others.

Advantages of soilless mediums:

  • Shelters the roots, giving them room to grow and spread out
  • Keeps the roots hydrated and aerated
  • Acts as a channel for nutrient intake
  • Anchors the plants
  • Provides structural support and keeps the plants upright

2. Water

All living organisms need water to survive. Essentially, it is the foundation of life. But why is it so important for cannabis plants? Apart from playing a role in sustenance, it also helps maintain plant structure, evaporative cooling, and supports other vital processes.

Why marijuana plants need water:

  • Helps the roots absorb nutrients from the medium
  • Transports and distributes nutrients through the plant
  • Needed for photosynthesis
  • Facilitates gas exchange and carbon dioxide intake
  • Helps the plants regulate their internal temperature
  • Maintains turgor, keeping the plants sturdy and structurally sound

At this stage, you need to be aware that simply any amount of water will not do. Marijuana plants have specific moisture requirements, mainly depending on the growth stage, environmental conditions, and growing method. And it is the interplay among these factors that dictate when, how often, and how much water you should provide.

Since there are no fixed rules to follow, it could get tricky. But, the importance of providing the right amount of moisture cannot be stressed enough. If the plants receive too little or too much water, their growth and overall well-being suffer, resulting in lower yields.

Overwatering, in particular, could be fatal. It chokes the roots and restricts their oxygen intake, preventing them from carrying out their tasks. Eventually, the roots may starve and begin to decay. If left ignored, the plants could die.

In the end, the only way around this is to learn good watering habits early on. More than that, you need to know and recognize the tell-tale signs of under-watering or over-watering to address the issue before it escalates.

3. Nutrients

Marijuana plants need nutrients to fuel various processes, including growth and reproduction. As the plants grow, their nutritional requirements change. If you fail to meet them, the plants may experience stunted growth and be more vulnerable to pests, molds, and diseases. Overfeeding is equally harmful and could cause potentially irreversible damages. It is important to make the right marijuana nutrient mix.

Keep in mind that the pH level plays a crucial role in nutrient availability and uptake. If the root zone is too acidic or too alkaline, then the roots would not absorb certain nutrients, resulting in deficiencies. To avoid this problem, ensure that the pH level falls within 5.5 to 6.5 at all times.

Cannabis plants need two types of macronutrients and micronutrients.

Macronutrients

These are the nutrients that the plants need in high amounts. The macronutrients include nitrogen (N), phosphorus (P), and potassium (K). They are expressed as NPK ratios, indicating the percentage of each nutrient in the mix. Ensure that the NPK value of your chosen nutrient mix is suitable for the plants’ current growth stage.

The table below gives you an idea of how much nitrogen, phosphorus, and potassium cannabis plants need.

Growth Stage Nitrogen (N) Phosphorous (P) Potassium (K)
Vegetative High Medium High
Flowering Low Medium to High High

Micronutrients

These refer to nutrients that marijuana plants need in small quantities. Even if only in trace amounts, they are nonetheless essential to growth. Deficiencies and toxicities are rare but could happen. If so, they could severely compromise plant health, growth, and yields.

Some of the micronutrients that cannabis plants need are:

  • Boron
  • Calcium
  • Copper
  • Iron
  • Magnesium
  • Manganese
  • Molybdenum
  • Sulfur
  • Zinc

4. Light

Plants need light for photosynthesis, the process by which they create food from water and carbon dioxide. Glucose – the manufactured food – is then used to fuel growth and other metabolic processes.

To keep cannabis plants healthy and productive, make sure to provide just the right amount of light. Insufficient light reduces their ability to photosynthesize, which could slow down or even halt growth. And as the plants stretch out in search of more light, they turn tall and spindly, making them weak-stemmed and structurally unstable. An excess, on the other hand, could cause light burn and heat stress.

When we talk about the amount of light, it can mean one of two things – light duration and light intensity.

Light duration indicates how many hours of light the plants receive in a day. While an excess of it can affect the plants’ growth cycle and budding, it generally does not limit their ability to continue growing.

Light intensity, on the other hand, refers to brightness. For example, the more intense the light during the flowering stage – provided it is the correct wavelength – the higher the yields. Any excess of light can become detrimental and harmful.

Light Schedule

Cannabis plants – except for plants grown from autoflowering seeds – are naturally photoperiodic. They transition to a new growth stage after receiving certain hours of light and darkness in a day. To begin flowering, for instance, they will need “short days and long nights.”

Outdoors, this happens naturally as the days start getting shorter than 12 hours. If growing indoors, you would have to trigger the flowering phase by switching to a 12-12 light cycle, exposing the plants to 12 hours of light and 12 hours of darkness every day.

The recommended light schedule for every growth stage.

Growth Stage Light Schedule
Seedling 18-6
Vegetative 18-6
Flowering 12-12

Light Intensity

There are warning signs if the plants are getting too much light. You would notice the leaves starting to turn pale or yellow, curl, and wilt. If you encounter any of these and other signs of heat stress, increase the distance between the bulbs and the canopy immediately. Note that this problem is more likely to occur if you are using high-intensity discharge (HID) lights, such as metal halide (MH) and high-pressure sodium (HPS) lamps.

If you have a lux meter, then you can measure the intensity of the grow lamps across different points in the growing space. It allows you to pinpoint which areas are receiving optimal or excessive amounts of light. In turn, you can rearrange the plants as needed or tweak the lighting setup. Either way, you get to boost growth and maximize yields.

Light requirements across the different phases of growth.

Growth Stage Light Intensity
Seedling 5,000 to 7,000 lux
Vegetative 15,000 to 50,000 lux
Flowering 45,000 to 65,000 lux

5. Suitable Temperature and Humidity Levels

Marijuana plants prefer an environment that is neither too warm nor too cold, nor is it too dry or too wet. In other words, you want an optimal balance of both temperature and humidity. And to understand how these two are interrelated, you need to know what they do in the first place. Check out our article on how to control indoor humidity for further information on maintaining an optimal growing environment.

Temperature

Temperature affects the plant’s ability to grow and photosynthesize. In particular, it could increase or decrease the rate of photosynthesis. The right temperatures allow the plant enzymes to catalyze the photosynthetic reactions more efficiently, resulting in rapid, vigorous growth.

In contrast, extreme temperature fluctuations could interfere with photosynthesis, slowing down growth. Too-hot conditions also make the plants more susceptible to pests and diseases. At the same time, freezing temperatures could shock or even kill the plants overnight.

Humidity

Improper humidity levels can also be detrimental.

Note that when we talk about humidity, we refer to relative humidity (RH). It is a measure of the amount of moisture the water can hold at a given temperature, expressed as a percentage. In general, the hotter the air is, the more water it can hold.

If the humidity is excessively low (translating to dry air), the plants are more likely to lose moisture. In response, the stomatal pores – the leaf openings – will close to prevent further moisture loss. However, doing so also reduces their intake of carbon dioxide – a key ingredient in photosynthesis. Without enough carbon dioxide, the plants would eventually fall sick and die off.

Overly humid or moist conditions, though, are just as harmful. This makes cannabis plants more prone to fungal and bacterial infections. Left unaddressed, these diseases could spoil or even decimate your harvest.

Given the dangers of improper temperature and humidity levels, make sure to keep an eye on them at all times. If you are growing outside, you may not have full control over these factors. Indoors, thermometers and hygrometers are your best friends. You can also manipulate the environment using various equipment, including air-conditioning units, heaters, humidifiers, and ventilation systems, among others.

The recommended temperature and RH values.

Growth Stage Temperature (During Lights on) Temperature (During Lights off) Relative Humidity
Seedling Around 77°F (25°C) Around 70°F (21°C) 65-80%
Vegetative 71–82°F (22–28°C) 64–75°F (18–24°C) 55-70%
Early Flowering 68–78°F (20–26°C) 61-72°F (16-22°C) 40-50%
Late Flowering 64–75°F (18–24°C) 61-68°F (16-20°C) 30-40%

Keep Your Marijuana Plants Healthy and Productive

Meeting the primary needs of marijuana plants is the key to a successful growing operation. And if you understand what makes these elements important, you could provide them better and more efficiently. In turn, it guarantees healthy growth and generous yields. By and large, it all comes down to giving the plants a place to grow, a means of sustenance, and the right environmental conditions.

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