Most cannabis growers will tell you that the seedling phase is the most important of all the stages of cannabis plants’ life. Royal Queen Seeds recommends that whether you are growing marijuana from seeds or from a clone plant, the hands-on part of cultivating cannabis starts when the plants are still in their seedling phase. A crucial part of the seedling phase is when you will transplant your juvenile plants to a larger pot or in their final pots. If you get this stage wrong the growth of your plants could be lost.
Why is it important to care for cannabis seedlings?
After germination or after cutting a clone from the parent plant, the seedling needs a place to take root. The objective is the development of a healthy root system or root zone. If your seedlings find it hard to grow this now, it’s likely they will never be able to recover it is also more likely that your seeds won’t reach their full growth potential. Some seedlings that fail this early might not even grow at all. Therefore when you buy marijuana seeds, you need to ensure that your seeds are fresh and viable so that these will sprout or germinate.
The best growing environment for seedlings
When your seeds have germinated, these will be called seedlings. These fragile, juvenile cannabis plants need to be treated delicately. You need to care for your plants like you would your own child because these will rely on you for almost all its growing needs. If you intend to grow it in outdoor soil, you will make sure that your outdoor climate and environment is conducive to growing this strain of cannabis. If you will grow your cannabis indoors, inside a growing room or tent, you must make sure that your seedlings get the best growing environment including lighting, soil, air, and nutrients.
Seedlings may also be very frail and may need extra support. You can prop this with a small stick or a toothpick and some garden wire. You must also provide an 18/6 light/dark schedule because this is ideal for seedlings.
There are many forms of grow lighting but the most conducive is white light. The source of light should be either CFL, MH, or LED. But if your growing room has a window that gets enough daylight then this could do for now.
Unknown to most growers, roots grow in the dark. This is why you need to use an 18/6 or 20/4 light/dark schedule on a nonstop 24-hour light cycle. High humidity is needed at this stage at 70% RH, and temperatures in the 20–24°C range. These are perfect seedling settings and will not apply to the next stages of a cannabis plant’s life. You need a propagator; thermo-hygrometer and a spray bottle of water are your tools to help you create that perfect humid environment that seedlings love.
You will notice at this time that there are plants that will have stretchy or floppy growth. Don’t worry because this is not your fault. These may be due to genetics. Often, it’s an indication the grow lamp is positioned too far away from the canopy. A cool white 250W CFL can comfortably hang 15cm above a dozen or more seedlings without burning the leaves.
Choosing the ideal starter substrate material
Your seedlings’ growing medium should be wet but not waterlogged. A wet-dry cycle should be your goal. Do not overwater your plants because this can cause mold and root rot. Mist plants with a sprayer if you are unsure. To test for the medium, touch it and feel how dry or how wet it is. This is a good way to decide if you need to adjust the humidity levels inside your growing area. You must remember that starting in one medium and switching to another can be hazardous. You must keep this simple and consistent. You can’t start growing seedlings in soil and transplant these later into a bucket.
All about choosing cubes, cups and other small containers for planting
You may use cubes and blocks for hydroponic growing. Your seedlings should be placed in a small cube so that this can be transplanted easier later. Cut a cube-sized chunk from a larger block. This is a good way to transplant cannabis plants without adding too much stress to the seedlings.
There are so many types of cannabis cubes but of all the recommendations, Rockwool may not be a good idea for people who want to continue soil growing. Rockwool retains more water than the surrounding soil and these results in a green, sludge-like algae growth in the soil. So don’t take the risk of your seedlings dying from root rot.
An oxygen-rich medium that will drain excess water and nutrients well is the best mix for soil growers and coco coir growers. From these two materials, there is an overlap during the seedling stage. Coco cubes or peat are usually the easiest to use and are also very expensive as well. The same as rockwool blocks, you will be able to monitor root growth as the white strands usually stick out from the cube. Those who would like to grow in organic and hydro or those who are growing clones usually have the highest success rate when seedlings are started with cube growing mediums.
There are also soil and coco growers who use small plastic pots or party cups as starter containers. Lightly fertilized soil combined with perlite or coco with 30–50% perlite is usually the most widely chosen mixed media for cannabis seedlings. As long as the bottom of the container has plenty of drainage holes and the interior will be able to hold the volume of medium, this can suit as your starter pot. You can also improvise by using coffee cups, plastic party cups or any small cup. Just poke small holes at the bottom.
Transplanting seedlings and when to do it
When is the right time to transplant seedlings? The best time is before they outgrow their current container or pot. The advantage of cubes is that you can see roots poking out which means that it is time to transplant to a larger cup. When you start with a cup or small pot, you are only relying on clues that are above the ground or medium. Usually when the sets of true leaves of the seedling have appeared and have covered the circumference of the container then this is the right time. Vertical growth of the seedling is another obvious clue.
But do not wait very long to transplant. Plants can get root bound and this can put stress to your plants. It could take time for root bound plants to recover too and plants can remain stunted forever. Usually, it could take 7–10 days for a seedling to take root and is ready for transplant.
How to transplant cannabis seedlings safely
Where you buy marijuana seeds, you can ask for good starter cubes to grow your seedlings. Cubes are the easiest to work with because you can safely transplant your cannabis plants. You can either cut a hole to size from a bigger block or create a hole into the medium using your fingers and insert the cube for a good fit.
Potting your plants should be done safely. First, don’t fill your big container with soil all the way. Leave room to water the pot later. Packing the pot with soil to the top will just cause water to spill from the pot and it won’t be absorbed by the soil to reach the roots.
Create an impression in your large container using a small pot. Make this impression in the medium after you have watered the soil. This will be the perfect spot where you will place the transplanted seedling.
Wait until the medium in the small pot is dry before transplant. Turn the dry plant upside down, and pat the bottom. Hold the plant stem from the base and remove it from the compacted medium out of the container all in one piece. Slide the plant into the large container. The place lost topsoil or coco and add a little more water.
Should you use small pots or big final pots
If your final container is up to 11l, you can sow seeds directly. This is only the viable option when growing to start from a cannabis seed. Clones will not take root in a large container. Usually, seedlings in large pots will grow slower than those in smaller containers. After a few weeks of growth, you will see the obvious difference is negligible.
If you don’t transplant, you can reduce the possibility of transplant shock. However, you will limit the potential of your plants. Usually, a first and final transplant is the best option for autoflowering strains that have a short flowering cycle like autoflowering cannabis plants. Bigger pots are always better. Transplanting is stressful but it should not be avoided. You must practice perfecting this technique to avoid plant stress for your future plants.