Temperature & humidity
Now that you have successfully germinated your seeds, it’s time to care for the resulting seedlings that sprouted. At the beginning of their life, seedlings need to be checked on regularly and prefer the warmer more humid end of the ideal ranges for vegetation. If this is your first or second grow, this is especially important. The first few weeks are crucial as the plant is very sensitive to its environment. Also, their size makes them more vulnerable to problems. You’ll want to take the first week to try to fine tune your environment so that it is consistent and in the ideal ranges. This will produce the best results.
Ideal ranges for plants in seedling stage or vegetation:
- Temperature – 70°-85°F/20°-30°C
- Humidity – 40%-60% RH (You can go as high as 70% during the early seedling stage)
Once your plant starts showing sex; either female pistils or the male pollen sacs. You can remove the males and start flowering your female plant(s). If it’s a photoperiod plant, you do this by changing the light cycle from 18-6/20-4/24 to 12/12. If you’re growing an autoflowering strain, it will automatically start to flower without any changes to the light schedule.
Ideal ranges for flowering plants:
- Temperature – 65°-80°F/18°-26°C
- Humidity – 40-50% RH
- Late flower – 25-40% RH
Flowering plants prefer cooler temperatures and lower humidity. During late flower, you can use a dehumidifier to lower the humidity as low as you can to cause a stress response by the plant in the form of more trichomes/resin production. For both vegetation and flower, night time/lights off should be between 5-10° cooler.
You want to make sure you have enough light for your plants. The amount of light the plants receive directly affects your yields. If you use less light, your yields will be limited. The best way to figure out how many watts you need is by first figuring out your canopy’s square footage. For this equation, you need to use the square footage of the canopy and not the entire tent/grow space. Then, you figure you need about 50 to 75 watts per square foot.
Light spectrum can also affect the way your plant grows. The more blue spectrum will result in taller and less bushy plants. While a more red spectrum will result in shorter and bushy plants. Full spectrum LED lights take advantage of the light spectrums and give the plants optimal colours for different stages of growth. This helps plants to grow as fast and healthy as possible. For HID lights, the metal halide bulb is in the blue spectrum and is best suited for vegetation. While the high pressure sodium bulb falls into the red spectrum and is better suited for flower. Although, a high pressure sodium can be used through an entire grow.
During vegetation, you want to have more light then darkness. The exact cycle is up to you. You can choose 18 hours of light with 6 hours of darkness, 20 hours light with 4 hours of darkness or 24 hours of straight light. For photoperiod plants, you need to change the light cycle to trigger the budding process. Changing the cycle to 12 hours of light and 12 hours of darkness will start flowering the plant.
Ph levels are an important part of the puzzle. You’ll want to keep your pH in the range for the entire grow with slight variations in the exact pH reading to allow different nutrients to absorb more efficiently. You can use pH up or pH down solutions to pH balance your water. You can also use lemon juice as a natural pH down, but if you do, a little goes a long way. I add about 2 ml of lemon juice to approximately 1 gallon of water. This amount of lemon juice is dependent on the starting pH value of the water. My water starts at about 7.0. And again, pH ranges depend on the medium you are using. For more information about The importance of pH levels for your plants click the link.
Ph ranges for optimal nutrient absorption:
- Soil – 6.0-7.0
- Coco coir/Soilless medium/Hydroponics – 5.5-6.5
Watering your plants
When seedlings first sprout, you only need to water a small circle around the plant. If you saturate the entire pot of medium, you increase your chances of over-watering your seedling. As your plant grows bigger, you can increase the size of the watering circle. Once the plant is about 8 inches to a foot high, you can start to water the entire pot when you water the plant. From that point on, you can saturate the entire medium in the pot. As plants get bigger, their thirst for water increases as well. Always monitor the top inch or so of medium to see if your plant needs water. This is especially important as the plants get bigger.
If your temperature and humidity are within the ideal range, try to water your plants every other day. Make sure to monitor the plant after you water it so you can see any signs of under or over-watering. They can both have similar symptoms but you should be able to tell the difference based on the medium. If it’s usually moist, it’s probably over-saturated with water. If your medium is usually dry, it’s more than likely under-watered. The key to watering your plants is to saturate the medium around your plant and let the top of the medium dry out before watering again.
Once your seedling sprouts and looks healthy and strong, you can start using a fan to create a light breeze. This not only moves the air around the grow area but also strengthens the plants stem. Once the plant gets bigger, you can increase the fan speed. You’ll want to place a fan on the ground or very low and another higher up to create good airflow. Unless you’re growing in an open space, it’s a good idea to also use an exhaust fan system to replace the warmer air with fresh, cooler air. This also gives your plants a steady supply of CO2 from the fresh air.
If you’re growing in a tent, you may want to use supplemental CO2 to supply your plants with constant carbon dioxide. This is essential in the photosynthesis process. There are both pre-made products you can purchase or DIY recipes to make your own. If you use these, you will need to keep temperatures a little higher. I have no experience using these yet but I may try it out in the new tent.
LST and other plant training
In vegetation, you’ll want to do the desired plant training techniques (ex. LST, ScrOG, Topping, Supercropping, etc.) to your plants. Then, once you have the plant the shape you want it and approximately half the height you’d like the plant to have, you can flower it or let it automatically flower. You can continue training into the first few weeks of flower. If you’d like to read more about the types of training, check out my previous blog post, Plant training techniques to increase yields
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