Growing Cannabis Indoors: Useful Tips + Seed Guide

Indoor cannabis growth depends heavily on genetics and quality of the artificial lighting. Generally, labels such as “indoor” or “outdoor” are a bit arbitrary when it comes to strain seeds. What we actually mean by the term “indoor seed”, is the strain’s ability to survive in climates that most resemble artificial environments and its response to plant training.

In this article, we are going to take a look at our top-10 indoor marijuana strains. But before we do that, let’s quickly look at some of the most important factors of indoor growing, besides seed genetics.

Setting Up an Indoor Grow Room

Even great indoor seeds need a space to grow! Creating a suitable marijuana grow room can be as simple or as complicated you want, depending on budget and the components you will use. In any case, it will require some planning ahead and some expenses are inevitable. It is a good strategy to outline your grow room using pen and paper first.

What are the most important factors when creating a perfect marijuana grow room?

Picking a Suitable Space

It can be a garage, a basement or a closet. There are people who have turned their old PC towers to grow spaces. The possibilities are endless, but before you get started, you should be aware of the plants you want to grow and what sort of growing style you will employ.

For larger-than-average marijuana plants, expect about four plants per square meter (3sq.ft.). Average plants give you more overhead (nine per 3 sq.ft.). Things get trickier with smaller plants, as you will need to use training to keep them under control. Under optimal conditions, you can fit more than 20 per square meter.

It is very important that your grow room is absolutely light-proof as this is of the utmost importance later on. Grow tents are a great solution, as they come in many sizes, with all the necessary components for a grow. Confined spaces (closets or cupboards) usually make for awesome grow rooms, however, if you have the knowledge, you can go wild!

Here are some key things to have in mind when selecting a grow room:

  •  Make sure it is light proof;

  •  Check for adequate ventilation;

  •  Make sure you have enough room for maneuvering;

  •  Make measurements to ensure it is tall enough for the plants and the grow lights. Usually, you have to hang them about 24” away from the canopy;

  •  Make sure your pets don’t visit the area.

Choosing a Growing Medium

There are quite a few choices of growing mediums when it comes to indoor gardening in general and marijuana cultivation in particular. Hydroponic, soil or aeroponic systems are all great ways to grow your plants, that all, however, present different challenges and benefits.

You can read our article on growing mediums before you start. Do your research and decide for yourself what suits you best. Soil is the simplest method, hydroponic methods are cleaner and aeroponics is best suited to advanced growers.

Finding the Perfect Grow Lights

You’ve found a home for your plants. Now you have to provide them with high-quality nutrition! As you know, plants photosynthesize their food, so a high-quality, intense grow light is the second most important investment you’ll make as a grower (the first is purchasing indoor seeds with great genetics).

There are many types of grow lights on the market:

  •  High-pressure sodium (HPS)

  •  LED

  •  Fluorescent (CFL)

Read our detailed guides on grow lights to decide what’s best for you. LEDs are all the rage right now with their cooler running temperatures and full-spectrum. However, there are still many growers that believe HPS systems are always a reliable choice, even though they tend to be more energy consuming and build up heat faster.

When installing your grow lights, you’ll want to make sure that you keep enough room for airflow above and under the unit, to ensure proper ventilation and room for your plants to grow. According to their genetics, plants will become either tall or stocky, so adjust accordingly. Using adjustable chains and hangers will help you a lot during your grow. A good rule of thumb is to keep the light about 1’ from the ceiling and 10-32” away from the canopy. The stronger the grow light, the farther it should be kept from plants.

Creating the Perfect Environment

In order for your marijuana plants to thrive, you must also create a great environment for them to live. You will need to ensure that air circulates within the grow room, but there are also factors like temperature fluctuations, humidity levels and even CO2 supplements that need constant management.

Some of the tools you will need are:

  •  Humidifiers/Dehumidifiers (According to the area you live in);

  •  Humidistat;

  •  Thermometers;

  •  Fans (for temperature and ventilation);

  •  Light timer.

Humidifiers need to be cleaned frequently to avoid infection and breeding of bacteria. According to the U.S. Consumer Product Safety Commission, humidifier water needs to be replaced daily and the device must be kept clean at all times. Also, they suggest that humidity levels should never go above 50%, as humid and dark environments are for bacteria what dry and well-lit environments are for rattlesnakes.

In order to ensure the perfect temperature, make some test runs with the lights on and add as many fans as needed to keep the levels between 60 - 80ºF (20 - 26ºC)

Achieving Higher Indoor Yields With Plant Training

Just as humans get stronger by challenging their limits, plant training means deliberately manipulating plants into adverse conditions, so they grow healthier and give more abundant yields. There are many ways to train marijuana plants, and we suggest that you learn all about it before starting to avoid unwanted damage to your crop.

You could always let your plants grow as their genetics intended, but keep in mind that marijuana plants are designed to utilize sunlight and not artificial lighting (which will always be inferior to natural light). That’s why, you must at least try to change the shape of your plants in order to increase light penetration, using some technique like Screen Of Green (SCROG) or Sea of Green (SOG). Altering the natural “Xmas tree” shape of the marijuana plant offers better light distribution and increases bud production.

Feminized, Autoflowering Or Regular Seeds

You can not know the sex of your seeds until they reach the flowering stage. The chances are 50-50, depending also on the environment. If marijuana plants are under a lot of stress, they can even turn into hermaphrodites, meaning that they will pollinate themselves. Unless you are a breeder, you don’t need male and hermaphrodite plants. So, if you are choosing seeds with the sole purpose of consuming the bud, do yourself a favor and get feminized seeds from reputable seed banks.

But what exactly are feminized and auto-flowering seeds?

Feminized Marijuana Seeds

As we stated above, the sex of marijuana plants is impossible to be determined right off the bat. However, feminized seeds come from a cross between male pollen from a hermaphrodite plant and a female flower. The result is a plant that it is almost certainly a female (although it can turn into a hermie if you are not careful) and never a male.

Feminized seeds give a tremendous advantage under artificial lighting, outdoors or in the greenhouse. They will deliver optimal quality as well as show the strongest characteristics of the strain. The quality, taste, flavor, and potency (THC/CBD %) of marijuana produced from feminized seeds is significantly higher than those produced by nonfeminized seeds.

Autoflowering Marijuana Seeds

Changes in marijuana development are in sync with changes in the photoperiod. As light gets scarcer (winter is approaching), flowering is triggered for marijuana plants. Indoors, you can induce flowering to mature plants by reducing the amount of light they take per day (photoperiod).

Autoflowering plants begin flowering without any external input. After they reach a certain height, they will start blooming regardless of the light they are taking. However, this comes at a cost, as autoflowering seeds will not produce nearly as much yield as a feminized seed. After all, changing the photoperiod of your plants is not as hard (it’s literally all about setting a timer). Also, you can’t clone autoflowering seeds, so you’ll need to buy new ones after each life cycle.

Top 10 Marijuana Seeds for Indoor Growing

Barneys Vanilla Kush Feminized Seeds

Vanilla Kush, a unique indica strain is a combination of Afghan and Kashmir seeds. The bushy plant reaches a medium height giving dense yields with gold and red calyxes. Coming from Barney’s Farm in Amsterdam, the strain won the 2nd place overall at the 2009 High Times Cannabis Cup. The mixture of vanilla and lavender aroma in tandem with a hint citrus is without a doubt a gift to the senses.

This strain’s flowers are soft, large and light green with notes of orange. Vanilla Kush contains often over 20% THC, potentially too strong for beginners. When grown indoors the plant needs 9 weeks to blossom, reaching approximately 60 centimeters. Methods such as Sea of Green and Screen of Green are a good match for Vanilla Kush.

Affecting mostly the body, this strain offers a strong, relaxing, couch sinking high that lasts about two hours or longer. Mind-wise its effects are lighter; it gives a freeing feeling and might as well be a source of inspiration. However, newbie users should be careful. Vanilla Kush can be used for a variety of purposes including insomnia, mood disorders, nausea, arthritis and pain relief.

Type: 80% Indica - 20% Sativa

Height: 3’ (100cm)

Flowering time: 55-60 Days

Awards won: 2nd for Overall at High Times Cannabis Cup 2009

Yield: 600 gr/m²

Feminized: Yes

Autoflowering: No

Growth difficulty: Normal

THC level: 20%+

Green House White Rhino Feminized Seeds

The indica dominant strain Green House White Rhino is named after its sturdy thick appearance. The plant with immensely dense kolas frosted with white THC crystals has a common lineage with the White Widow.

Green House White Rhino Feminized is rather easy to grow and gives enormous yields with immensely compact buds that push the crops’ weight up. It can grow even in harsh environments. While the strain suits perfectly SOG setups it also responds specifically well to hydro systems.

Sweet flavored and undoubtedly strong due to its indica potency, Green House White Rhino Feminized can result in deep relaxation and sleepiness making it quite popular in the medical marijuana communities. In cases such as sleeping disorders and pain relief medical marijuana dispensaries often recommend the use of this particular strain.

Type: 90% Indica - 10% Sativa

Height: Very Tall

Flowering time: 9 Weeks

Awards won: High Times Cannabis Cup 1996 (2nd)

Yield: Very High

Feminized: Yes

Autoflowering: No

Growth difficulty: Easy

THC level: ±11%

White Widow

The White Widow, a legendary marijuana strain is an indica dominant hybrid (about 50-75%) with low CBD yet high THC levels, reaching over 20% in some cases. Nowadays, it has become difficult to say which seeds on the market are the “original” ones since all the big seed banks have their own White Widow strain version.

In general White Widows’ yields vary from 300-40g/m2 to 800 g/m2 depending on the breeder. However, the strain’s bud is super strong and you only need a small proportion in order to feel its effect. That means you don’t need a big yield; a lot of growers are happy to have only three plants.

While certain strains have a cerebral, upbeat and pleasant high, they all have a heavy effect on the body, offering not just a simple couch sinking effect but a rather strong and deep relaxation. White Widow’s sedative and narcotic effects have often proved valuable for medical purposes.

Type: 50% Indica - 50% Sativa

Height: Medium

Flowering time: 7-8 Weeks

Awards won: 2010 High Life Hemp Fair Hydro 3rd, 2014 High Life Hemp Fair Hydro Cup 3rd

Yield: 400-800gr/m2

Feminized: Yes

Autoflowering: No

Growth difficulty: Easy

THC level: 15-25%

Barneys Blue Cheese Feminized Seeds

Blue Cheese by Barney’s seeds, is one of the most characteristic odors and taste wise strains on the market, combines an original UK Cheese female (Skunk #1) Indica with a Blueberry male one. The strain is also among the strongest on the market, with THC levels reaching 20%.

This fast flowering, indica dominant plant is easy to grow. It has a compact, heavy kola while also strong side branches that fill with thick sticky buds. As such, Blue Cheese strains are perfect for SOG and SCROG yield improvement methods. In case discretion is vital for you, bear in mind to control the odor.

The mixture of the savory and sweet aromas of blue cheese and berry create a creamy intense yet fruity flavor resembling that of the authentic cheese. Promising a powerful, relaxing high, Blue Cheese Feminized is ideal for ending the day and simply enjoying the couch, while it is also used for stress, pain, and muscle spasms relief.

Type: 80% Indica - 20% Sativa

Height: 3ft (90cm)

Flowering time: 7-8 Weeks

Awards won: None

Yield: 650gr/m2

Feminized: Yes

Autoflowering: No

Growth difficulty: Easy

THC level: ±20%

Dutch Passion Power Plant Feminized Seeds

The Passion Power Plant, from the Dutch Passion Seed Company, come from sativa strains in South Africa. Although it has high THC levels (15%) this strain is not among the strongest ones on the market. The plants grow relatively fast compared to most sativas, needing around 7 to 9 weeks.

Passion Power strains produce either very big buds along with smaller ones (“popcorn” buds) or a large number of medium-sized flowers. Although this strain is easy and good to grow in most environments if you decide on indoors you’ll need to be prepared for a strong earthy and woody odor. Due to its high THC levels, this spicy peppery flavored sativa strain can result either in a pleasant and creative high or in a rather intoxicating experience.

Type: Sativa

Height: Medium

Flowering time: 8 Weeks

Awards won: None

Yield: High

Feminized: Yes

Autoflowering: No

Growth difficulty: Easy

THC level: 15%

Barneys Pineapple Chunk Feminized Seeds

The Pineapple Chunk, an indica oriented hybrid is a combination of Barney’s Pineapple with Cheese and Skunk #1. The plants strong and stable deliver great levels of THC (16-26%) with a smaller amount of CBD and are available at Barney’s as an autoflowering variety.

Extremely resistant to disease and mold, this strain is ideal for indoor environment and goes into flowering in just 8 weeks. Under the correct conditions, the Pineapple Chunk proliferates well and is overall a good start for new growers.

With a mixed odor of cheese, sweet pineapple, and tangy skunk, Pineapple Chunk has pain and stress relief results. The strain has a heavy body effect and a lighter fast buzz. Some users claim they experience a cerebral energy which means it is not ideal for conditions such as anxiety and insomnia.

Type: 80% Indica - 20% Sativa

Height: 3ft (100cm)

Flowering time: 8 weeks

Awards won: 1st for Indica Cup at High Times Cannabis Cup 2009

Yield: 600gr/m2

Feminized: Yes

Autoflowering: Yes

Growth difficulty:

THC level: 16-26%

G13 Haze

G13 Haze, a legendary marijuana strain, is one of the most potent cannabis plants on the market. Rumour has it that it was crossed by Dutch breeders after deriving from a US government research lab. The strain has a THC level of about 18% and a classic Indica knock out effect. It has won the 2nd place at the 2006 Cannabis Cup.

G13 Haze is not exactly fast flowering. It needs about 9-11 weeks to grow, while yields reach 450g/m2. Both odor and flavor have fresh and sweet notes with a somewhat astringent twist. The pleasant and smooth high is topped with a slight Sativa edge. G13 Haze is definitely a powerful strain, so if you are a low tolerance user you might want to be extra careful.

Type: 80% Indica - 20% Sativa

Height: Medium

Flowering time: 9-11 Weeks

Awards won: IC420 2006 (2nd)

Yield: 450gr/m2

Feminized: Yes

Autoflowering: No

Growth difficulty: Medium

THC level: 18%+

Green House Super Lemon Haze Feminized Seeds

Green House Super Lemon Haze marijuana seeds are closely related to the Super Silver Haze. The strain bears the best qualities of its first cousin together with some Lemon Skunk. Super Lemon Haze is a multi-award winner, having won two times at the High Times Cup getting the 1st place in 2008, then the 1st and 2nd place in 2009. In 2010 it won the 1st place at the IC420.

If you are growing Super Lemon Haze indoors you might need to control the plant’s massive size. You can try lollipopping, SCROG or LST methods. If you go for SCROG techniques, you will be rewarded with massive yields.

Green House Super Lemon Haze strains with the classic Haze flavor and the added citrus notes promise a combination of the sativa’s euphoric and clear high and Indica’s heavy body stone.

Type: Sativa

Height: Tall

Flowering time: 8-11 Weeks

Awards won: High Times Cup 2008 (1st), 2009 (1st & 2nd), IC420 2010 (1st)

Yield: 500gr/m2

Feminized: Yes

Autoflowering: Yes

Growth difficulty: Easy

THC level: 20%+

Lowryder #2 Autoflowering Feminized Seeds

Lowryder #2 Autoflowering Feminized seeds, bred by Joint Doctor, are a combination of Lowryder strain and a Brazilian hybrid, Santa Maria, famous for its resin-laden abundant buds and its powerful hit.

This fast flowering extremely potent strain needs about 9 weeks to flower. Just as all autoflowering plants it produces an average yield of sticky, aromatic buds especially when grown in a SOG set up. These qualities make the strain ideal for both hobbyists and commercial purposes.   

Lowryder #2 Autoflowering Feminized strain with its exotic, sharp flavor and odor, creates a euphoric high that due to its medium THC levels (12-14%) can be enjoyed by all users even the low tolerant ones.

Type: Sativa/Indica/Ruderalis

Height: Small

Flowering time: 8 Weeks

Awards won: None

Yield: Medium

Feminized: Yes

Autoflowering: Yes

Growth difficulty: Easy

THC level: 12-14%

Barneys LSD Feminized Seeds

LSD Feminized seeds, named after their strong psychedelic effects are a combination of Afghan Indica and Skunk #1. With THC levels reaching 25 % and 1,2% CBD, this strain is among the strongest on the market and has won the 3rd place in 2008 at the High Times Cannabis Cup.

This hardy, vigorous strain has strong resistance to various plant diseases and mold infections, while it responds well to diverse growing conditions and fits all growing media. When grown indoors the plants need up to 8 weeks to flower while the yields reach 700 gr/m2.

LSD has a musky, deep smell and an earthy flavor resembling chestnuts. The strain’s cerebral high creates both psychedelic, trippy feelings and euphoria while it is heavy on the body

Type: 70% Indica - 30% Sativa

Height: 3ft (100cm)

Flowering time: 8 Weeks

Awards won: 3rd for Indica Cup at High Times Cannabis Cup 2008

Yield: 700 gr/m²

Feminized: Yes

Autoflowering: No

Growth difficulty: Medium

THC level: 25%