How to buy seeds for indoor growing

Are you already looking forward to planting three plants in the tent after the new year, but can’t make sense of the overwhelming selection of seeds on the market? In our article we will explain in detail the most common terms you’ll encounter when buying and give you a few tips on which seeds are best for indoor cultivation.

When it comes to seeds of plants grown in controlled environments, it’s similar to wine. A name can reveal something, but it often won’t tell you whether you’re buying quality or whether you’ll like the result. Behind an interesting name there can be a cultivar that’s unsuitable for indoor growing or difficult to cultivate. When buying, think practically. The most important criteria when choosing seeds for indoor cultivation are plant structure and sex, length of maturation, and content of active compounds.

Sativa vs. Indica

Among growers it’s common to distinguish plants grown in controlled environments into sativas and indicas. Although experts debate the correctness of such a division, seed vendors use it to differentiate varieties with long maturation periods (sativas) from those that mature faster and have a more compact habit (indicas). The longest-flowering sativas can take more than 12 weeks to mature and can grow to enormous sizes. Pure sativas are therefore not the best candidates for indoor cultivation in a growbox, where space is limited. In addition, a long flowering period also means higher costs for the growing cycle. That’s why most growers choose either pure indicas or hybrids — crosses between sativas and indicas.

• Sativa varieties: Narrow-leaf varieties of plants grown in controlled environments with a long flowering time of approximately 10 to 12 weeks, originally from equatorial regions.
• Indica varieties: Broad-leaf varieties of plants grown in controlled environments originating from mountainous regions with a short flowering time of approximately 8 to 10 weeks.
• Hybrid varieties: Crosses between sativas and indicas that are selectively bred to achieve a certain plant type. Flowering time and plant structure depend on the combination of parental genes.

Photoperiodic vs. autoflowering varieties

Most plants grown in controlled environments are short-day and will start to flower only when the day length shortens below a certain threshold. In indoor cultivation this means the growing cycle is divided into two phases — vegetative, when the day length is 16–18 hours, and flowering, when the day length is shortened to 12 hours. The exception are autoflowering cultivars, which have been bred to flower independently of day and night length.

• Photoperiodic varieties: Short-day cultivars whose flowering depends on the photoperiod. Under indoor conditions they begin to flower only after switching to a 12/12 schedule.
• Autoflowering varieties: Varieties independent of the photoperiod that begin to flower regardless of day and night length, usually about 21 days after germination.
• Fast or early varieties: Cultivars labeled as early or fast are those with a quick onset of flowering and a short flowering period. These are not autoflowering varieties.

Feminized vs. regular seeds

Plants grown in controlled environments are dioecious and populations contain both males and females. Most growers focus solely on cultivating female plants for seedless flowers, as these contain the highest amounts of active compounds. This requires timely removal of males from the garden, which can be a challenge for inexperienced growers. That’s why most growers today use feminized seed, from which only female plants will grow. Regular seed also has its place — it’s used in breeding new cultivars and is important for conservation of the species.

• Regular seed: Seeds coming from plants grown in controlled environments pollinated in the usual way, from which both female and male plants will grow after germination.
• Feminized seed: Seeds coming from feminized parent plants grown in controlled environments, from which only female plants will grow.

Content of active compounds and terpenes

The main attraction of plants grown in controlled environments is the content of active compounds, primarily cannabinoids, but also terpenes and flavonoids. The best-known cannabinoid in plants grown in controlled environments is THC (tetrahydrocannabinol), which is responsible for many of this plant’s effects. Another important cannabinoid is CBD (cannabidiol), which, unlike THC, is not psychoactive. Based on THC and CBD content we divide plants grown in controlled environments into three chemotypes, noting that specific legal regulations apply to cultivation of plants grown in controlled environments with THC content over 1%. The same applies to large-scale cultivation of plants grown in controlled environments with THC content below 1%.

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• Type 1: Varieties of plants grown in controlled environments with a high THC content and a low CBD proportion. Modern cultivars can contain up to around 30% THC with trace amounts of CBD.
• Type 2: Varieties of plants grown in controlled environments with a balanced ratio of THC and CBD.
• Type 3: Varieties of plants grown in controlled environments with minimal THC content and a high CBD proportion. Registered type 3 cultivars with THC content under 0.3% are sometimes also referred to as industrial.

For more useful tips and guides for both beginner and experienced growers, follow our Higarden cultivation blog.