This is the second installment of our Seed to Harvest blog series, in which we will take a week-by-week approach to analyzing the growth stages of cannabis. Once again, the reference photos in this series have been generously provided by Future Harvest grower @treetrunk422. If you follow him on Instagram, he posts his amazing results using Future Harvest’s Dosaline line of premium powdered nutrients. This article will focus on a very fragile time in the cannabis life cycle, the seedling stage.

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Cannabis Seedling Week 1

A Germinated Cannabis Seedling growing gif

@Treetrunk422 germinated this seed using the paper towel method, then inserted them root down into a pH adjusted rockwool cube on a bed of Leca pebbles. The saturated rockwool will allow the seed to sprout and the Leca provides stability for the roots once it has matured. He is using a recirculating deep-water culture hydroponic system.

During the first week of the cannabis seedling stage, your plants are just beginning their journey to maturity. At this stage, they are delicate and require careful attention to ensure healthy growth. The main stem of the young plant will initially be soft before hardening in week 2.

Here are some general guidelines to follow in the initial stages, regarding light requirements, medium conditions, environmental conditions, and plant nutrition:

Medium: Keep the growing medium moist but not overly wet to support seedling development. The most popular growing mediums for cannabis are soil, rockwool, coco and soilless mix. These mediums are readily available at your local hydroponic store.

LED grow light ideal for cannabis growing

Light Requirements: Provide gentle light to encourage upward growth. A low-intensity fluorescent or LED light placed a few inches above the seedlings is ideal. Avoid intense light sources at this stage to prevent seedling stress or burning. Seedlings thrive under a cool-blue light spectrum, unlike the higher light intensity needed during flower development. We recommend CFL lights, fluorescent lights, or low-wattage LED light strips that advertise a 64,000K spectrum for starting seeds. High-intensity LED’s can often be dialed down by percentage to reduce the intensity.

Ideal Humidity Ranges for Growing Seedlings and Clones

Humidity: Maintain a humid environment around your seedlings, ideally between 60-70% humidity. This helps prevent dehydration and supports proper transpiration. You can achieve this by using a humidity dome or misting the air around the plants regularly.

Ideal temperature ranges for growing Seedlings and Clones

Temperature: Keep temperatures in the range of 68-77°F (20-25°C) during the day and slightly cooler at night. Consistent temperatures help promote healthy growth and root development.

Cannabis Seedling at Day 1

Cannabis Seedling at Day 1

Cannabis Seedling at Day 2

Cannabis Seedling at Day 2

Cannabis Seedling at Day 7

Cannabis Seedling at Day 7

Nutrients: Seedlings do not require additional nutrients during the first week. The nutrients stored in the seed provide ample nourishment for initial growth. Wait until the second week or week 1 of the vegetative cycle (week 3 from sprouting) before introducing gentle ratios of diluted fertilizers.

Cannabis Seedling Week 2

As your cannabis seedlings enter their second week of growth, they will start to develop their first true leaves and establish a stronger root system. The environmental conditions, nutrients and light requirements remain the same (mostly) as in week one. Here is what to expect during week 2 of the seedling stage.

True Leaves: By the second week, you should see the development of the first set of true leaves. These leaves will have a more distinct shape compared to the initial cotyledons and are a sign of healthy growth. The first set of true leaves consists of one leaflet, followed by sets leaves with three leaflets and then sets of five as roots are established. Once the young seedling has developed at least two sets of three-leaflet leaves, you can begin feeding your plant additional nutrients. This marks the start of Week 1 of the vegetative growth cycle.

Graphic identifying the True Leaf from the Cotyledon

Hardening Off: A seedling’s stems will start to become rigid as growth progresses and roots develop. You may see what appears shedding skin along the stem, this completely normal. If you notice excessive stretching during week 1, make sure to adjust the light source closer to seedling or increase the light intensity.

Watering: Water your seedlings as needed, allowing the growing medium to dry slightly between waterings. Overwatering can lead to damping-off or root rot, so be mindful not to saturate the soil excessively. Gently misting your seedling using a hand sprayer is a safe way to avoid overwatering.

Nutrients: While seedlings may still rely on stored nutrients from the seed, you can start introducing a very mild, balanced fertilizer during the second week. Dilute the fertilizer to half or quarter strength to avoid nutrient burn and provide essential elements for healthy growth. Gentle rooting formulas like Future Harvest’s Prop-O-Gator can be used in small dilutions to assist in root development. We recommend waiting about 5-7 days after a seedling has emerged from your medium before using a light dilution of Prop-O-Gator.

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Transplant Preparation: If you start your seedlings in small containers, you may begin preparing for eventual transplantation into larger pots or the garden. Ensure the new containers are clean and have adequate drainage holes to prevent waterlogging.

Be cautious not to overwater the seedling, as excess water can lead to "damping off", a common cause of seedling death due to fungal pathogens. Gently misting your seedling using a hand sprayer is a safe way to avoid overwatering.

Cannabis Seedling at Day 9

Cannabis Seedling at Day 9

Cannabis Seedling at Day 11

Cannabis Seedling at Day 11

Cannabis Seedling at Day 13

Cannabis Seedling at Day 13

By the end of the second week, your cannabis seedlings should be well on their way to becoming robust young plants, setting the stage for further growth and development in the vegetative phase. This marks the start of Week 1 of the vegetative growth cycle.

Two week old cannabis plant starting day one of the vegetative stage

This is a notable example from @treetrunk422 of a cannabis plant ready for week 1 of the vegetative cycle! This seedling is 14 days (2 weeks) from sprouting. It will have enough root mass to absorb additional nutrients AND enough photosynthetic surface area to be able turn light energy into stored carbohydrates for exponential growth.

To find Week 1 of vegetative growth dilution ratios for your Future Harvest Nutrients, try using our Future Harvest Nutrient calculator or reference our online feeding chart PDFs.The next blog in this series will cover the all-important vegetative cycle, from week one until flowering!

Navigate through our Seed to Harvest series to explore each stage of cannabis cultivation:
Germination Stage Seedling Stage Vegetative Stage Flowering Stage Harvesting Stage