9 Top Tips for the Seedling Stage

Once you have managed to germinate your cannabis seeds, the next step is to give them the best possible start in life. Your seeds will grow into seedlings, which is when they are the most delicate and need lots of nurturing and tender loving care. In this article, I provide my top tips to consider to help you grow the healthiest seedlings and prepare your crop for the vegetation stage.

Low Light Intensity Is the Best

When your germinated cannabis seeds sprout out of the growing medium, they will spend the next 2-3 weeks as seedlings. During this stage, you will need to be careful how much lighting you give them.

You do not want to expose them to high PPFD levels, nor do you want to provide them with insufficient levels of light. My tip here is to keep your grow light 16 inches above the seedlings and use a compact fluorescent or LED with a dimmer setting before they transition to the vegetation stage.

Avoid Hot Soils

Don’t be fooled by fancy packaging when buying soil to start your cannabis seedlings off. I prefer to use a combination of worm castings, coco coir, and compost to ensure the seedlings receive all the necessary nutrients without experiencing nutrient burn. My tip is to use a light potting mix and avoid soils that can be overfertilized. Always check the label of the soil when buying, and check the NPK ratios.

Always Check Your pH Level

The reason pH is so important when growing cannabis is that nutrients are most readily available within a specific pH range. Soil growers need to aim for 5.5 – 7.0, and hydro growers should aim for 5.5 – 6.5.

My tip here is to always check your pH levels and refrain from second-guessing or creating a nutrient solution before starting to feed. It won’t take long for your seedlings to experience nutrient lockout and begin to show signs of distress.

The Right Temperature and Humidity

Maintaining an optimal growing environment is essential during the cannabis seedling stage. Maintain your indoor grow room at 24 degrees Celsius with a relative humidity of between 65-75%.

Avoid letting the humidity drop below 60%. If necessary, frequently spray your seedlings and the pots to help maintain a consistent temperature and humidity, keeping the seedlings as stress-free as possible.

Fan Currents Make Seedlings Strong

One of the best ways to grow strong and durable seedlings is to use an oscillating fan and create a light breeze for your plants. The reason is that the stems of your seedlings will grow thicker and stronger.

Using a fan to blow a light current on your seedlings will help prevent tall and leggy seedlings that often tend to fall over. My tip is to keep an oscillating fan several feet away and set it to the lowest setting so you don’t overdo it.

Foliar Spraying Nutrients

Spraying your seedlings with a mild nutrient solution is an excellent way to supplement them with nutrients whilst the roots are developing. A very mild mix, typically around 1 mL per liter, is sufficient. When spraying, lightly mist the tops and undersides of the seedlings. Use an organic nutrient and spray every 24 hours.

 

Don’t Let Seedlings Stretch

There are several reasons why seedlings can grow tall and leggy and, within a week or two, start to topple over due to stretching. Keeping your grow light at a distance between 12 and 18 inches is optimal to avoid unwanted stretching, combined with using a fan to promote a strong stem. If you notice that your seedlings seem weak and lanky, try supporting them with a thin gardening cane and wire.

Always Label Your Seedlings

Growing multiple cannabis strains simultaneously is one of the benefits of indoor cultivation. However, not knowing which strain is which is a silly mistake that can be easily avoided by simply labelling the pots that your seeds are inside.

My tip is to buy some sticky waterproof labels and write the labels out before germinating your seeds. You would be surprised how easy it is to get your seeds muddled up and not know which are the correct ones until flowering time.

Start Autos in Big Pots

When growing autos indoors, the seedling stage is crucial for developing robust, large-sized plants that will reward you with excellent yields. There is nothing worse than growing autos indoors that do not exceed 45 centimeters in height and make you feel like you are wasting electricity, time, and energy.

My tip is to start your auto-flowering seedlings in a large pot, typically between 30-50 liters in size, and refrain from repotting them to avoid stress.

My Final Thoughts

Providing your cannabis seedlings with the best start in life should be a straightforward process. To ensure optimal growth, ensure that the temperature and humidity levels are correct, keep your grow light close enough to avoid stretching, and avoid exposing it to excessive light intensity.

Ensure that the growing medium contains sufficient nutrients, but avoid overfertilization, as this can cause nutrient burn. Be prepared to support your seedlings with gardening wire and thin bamboo cane if you notice the stems are becoming too thin and lanky. Good luck giving your cannabis seeds the perfect start in life!

Feature photo: This seedling is about to enter the vegetation stage. photo credit: Stoney Tark.