Weed seedlings health and care title.

Weed Seedlings Top Tips For Growing

The cannabis seedling stage is one of the shortest of the 4 cannabis growing phases and yet it plays an essential part in determining healthy growth of your plant. There are a number of factors which contribute to the healthy growing of weed seedlings:

Like all living organisms, cannabis plants need some basic ingredients to ensure healthy growth throughout their various growth stages. For a healthy cannabis seedling, its essential needs are:

  • Light
  • Heat
  • Water
  • Soil and container

In this article we will take a look at these aspects in greater detail as well as consider some of the common issues and also discuss the process of transplanting seedlings.

What is the weed seedling stage?

The cannabis seedling stage encompasses the early growth of a weed plant between cannabis seed germination and entering the vegging (also known as veg or vegetative stage). This applies for both feminized photoperiod and autoflower cannabis seeds.

Once a cannabis seed has successfully gone through the germination process, it sprouts and a small taproot emerges and begins to establish itself in the soil.

cannabis seed breaks the surface.

As the tap root grows downwards, the new plant breaks the surface of the soil and grows upwards, displaying its first seedling leaf, which is known as a cotelydon. This is plain and flat.

Within days ‘seed leaves’ begin to develop above the cotelydon. These have ridges and serrated leaf edges, and as the seedling grows these developing leaves start to form the distinctive shape of the classic cannabis leaf.

A cannabis seed grows into a seedling. Check out our Skunkworks video for some tips on growing healthy seedlings!

A cannabis seed grows into a seedling.

How long does this grow stage last for weed seedlings?

The cannabis seedling stage lasts from 2 to 3 weeks (if outdoors, then this stage can last a little longer, especially if the light is poor – such as a consistent run of overcast days).

During this time of the weed seedlings growth stage it may seem as if growth above the soil is quite slow, but most of the magic is happening under the ground.

In the first few weeks of a plant’s life its energy is focused on rapidly developing its root system. After this is established, upward growth accelerates and the seedling stage lasts until foliage starts to develop more comprehensively as side branches extend and fill out.

Essential tips for weed seedlings good health

Mendocino Skunk weed seedling.

During this phase of the growth period for weed seedlings, light, water and heat are the essential ingredients to fuel its fragile root system as it develops and the grow medium is also significant.

Planting tips for weed seedlings

There are two schools of thought regarding the planting of cannabis seedlings. Most growers will plant germinated cannabis seeds in small pots – although not too small as these will inhibit the development of the root ball.

Alternatively, some growers suggest that a seed should be planted in the pot it will spend its life in to avoid the stress involved with transplanting. However, a big growing pot may inhibit the seedling’s ability to absorb water.

The most popular route is to grow in a small growing pot and then transplant their weed seedlings (see below for more details).

Always use a specialist seed/seedling soil as the grow medium, as this will supply weed seedlings with essential nutrients for this phase of the cannabis growing process. The desired pH level is 6.0 – 6.5.

Watering tips for healthy weed seedlings

A small cannabis seedling inside a plastic bottle homemade biome.A cut down plastic bottle provides a biome for a young outdoor seedling. A cut down plastic bottle provides a biome for a young outdoor seedling.

In the early days, this should be done often, but in small quantities, to prevent drowning the roots which can lead to a condition called root rot (often referred to as ‘damping off’).

On the flipside, not enough water will dry out the root system. It may be the ‘most hated word in English’, but the key to a healthy seedling is keeping the soil moist!

  • As the plant is still small and seed leaves are developing, it’s a good idea to use a spray bottle on a mist setting.
  • To stop weed seedlings from drying out it is also a good idea to make a biome or humidity dome, from a cut in half plastic bottle to retain humidity.

Lighting tips for healthy cannabis seedlings

Young weed plants will be reaching up to the light as they grow, but it’s important that the light source isn’t too strong in the first 2 – 3 weeks.

  • If using lights then the soft light of a CFL or dimmed LED is more than enough.
  • If on a balcony or window sill, it is advised to avoid strong sunlight for the first week or two until the seedling is developed.

How much light do cannabis seedlings need?

Weed seedlings displaying some stretch.

The truth is that there is no prescribed amount of light that weed seedlings need. In nature – for example growing weed in a garden – cannabis seedlings will grow with what hours of daylight are available.

In the controlled environment of an indoor grow space, a minimum of 16 hours a day is recommended, although many growers will keep their seedlings under light for 18+ and some even 24 hours a day.

A common issue for young weed plants growing on a balcony or windowsill, is that they become ‘leggy’, or stretching, as they chase the sun (unless they are in a spot which enjoys sun all day). This can lead to imbalanced growth leading to stringy plants.

In the grow room the opposite is true, as having seedlings too close to the light, or indeed having the light too strong, can cause damage to seedlings, in the form of burn or drying out the grow medium.

Heating tips for healthy cannabis seedlings

Healthy cannabis seedlings thrive in a warm and humid growing environment. The temperature should be a constant 21 – 25°C (70 – 80° F).

  • It is easier to control the temperature indoors, and for best results building a small seedling shelf or cupboard in a warm space, and using an artificial light source will give the young marijuana plants the consistent environment they need to thrive.
  • A common issue for outdoor growers who start their seeds off in early spring on a balcony or windowsill is fluctuations in temperature.
  • If an indoor seedling space is not an option, consider protecting it with a homemade biome to provide a microclimate. That way it can be placed in a spot which will get sunlight all day and avoid stretching issues. As it grows, change up the bottle size!

Do cannabis seedlings need nutrients?

Weed seedlings definitely don’t need nutrients in the early stages of their growth, especially if grown in specialist seed and seedling soil. As they develop and begin to grow upwards and outwards, some growers will apply a very weak nutrient solution.

Growers are advised to research nutrient products on the market and the guidelines associated with their use.

Problems with cannabis seedlings

Aphids marching up a plant leaf.

Sometimes cannabis seedlings develop issues and, apart from the problems already discussed in relation to water, light and environment, the causes will be pest or nutrient based.

  • Pests: Keeping your growing space clean is the best way to avoid pest issues – with the most common villains being spider mites, whiteflies, and aphids. However, if identified, solutions such as spraying plants with neem oil or a weak soapy solution can be effective.
  • Nutrient toxicity can also be an issue for young marijuana plants; a soil mix can be what is known as a ‘hot mix’ with too much nutrient content.
  • Signs of nutrient issues can be droopy plants, yellowing leaves and ‘burnt’ or curling leaf tips.

Cannabis Seedling transplanting tips

The simple answer to the question of when to transplant cannabis plants is that plants need to be transplanted when they outgrow their growing medium.

See our Tips for Transplanting Cannabis Seedlings for further information.


To summarise, weed seedlings need to be cared for diligently as they are reasonably delicate at this early stage in a plant’s life. They require water, heat and light to thrive, but within these categories it’s important to get the balance right in order to avoid creating issues.

When the cannabis seed first emerges from its shell it will lay down roots below the surface of the soil and leaves above it. As the seedling stage progresses growth will accelerate and more leaves will begin to develop.

With careful management, the seedling will soon be on to the next growing stages such as the veg phase and the flowering phase (find more information about the 4 cannabis growing stages, one of our popular knowledge based blog articles).

In addition to following guidelines laid out n this article, the best guarantee for healthy seedlings is to buy cannabis seeds from a reputable provider.

A company like Paradise Seeds has a library of top quality cannabis varieties which have been researched and developed through an extensive breeding program.

Paradise cannabis strains – whether they are classic cannabis seeds such as Wappa, Atomical Haze, Nebula or Jacky White, or Californian varieties such as Tangerine Sorbet, Sunset Parad

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