After your seedlings have started, you are going to need to grow out your plants. That includes making sure they have a healthy medium to grow in, ample room to grow, plus enough light, food, water, and a cozy temperature and humidity. This process is called ‘vegetation’. Let’s dig in.

Transplanting Seedlings

Keep your seedlings healthy by keeping the growing medium moist, but not soaked, and by spraying the leaves with water once or twice daily. Once seedlings have established roots and grown to around 4 to 8 inches tall, it is time to transplant your marijuana seedlings. Growing vibrant and healthy marijuana plants requires you do so. The growth period between seedlings and mature plants, prior to flowering, is called the vegetative phase.

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Soil-less (hydroponic) growers will transplant mature seedlings into their preferred systems. The pH for soil-less gardens should be about 5.5-6.5. Indoor and outdoor soil growers will generally transplant seedlings into a size #1 through a #5 plant container. I grow in soil, both indoor and outdoor. When I transplant up, my soil mixture is one part (Pro-Mix) Coco Choir soil with one part (Fox Farms) Ocean Forest mix, which includes a fine blend of: earthworm castings; bat guano; fish meal and crab meal. A pH of 6.2-6.8 should be maintained in soil.

The best light for vegetating cannabis

When bringing plants outdoors, I like to get started as soon as the season allows. That means no more rain or freezing temperatures. I like to take the plants outside for extended periods during the day, over the course of a week or so, to let them get used to the bright sunlight and temperature variations of an outdoor environment. This is known as “hardening”,a process that keeps the plant from suffering too much stress (shock) when moving from one environment to another. While the marijuana plant is very hardy, shocking it can set its growth dormant for several days to several weeks.

It is important the plants have light for at least 14 hours a day in order to maintain vegetative growth and keep them from flowering. The growing season varies slightly by latitude. For instance, mid-summer days in the state of Washington are about 16 hours, while in southern California the mid-summer day is about 14 hours. Vegetative lighting preferences differ between indoor growers. Some growers prefer to use a lower watt High Intensity Discharge (HID) bulb for vegetative growth, say a 400w or 600w, while others might prefer to use the 1,000w bulbs typically used for the flowering cycle. The “Gavita” brand offers a professional line of lighting systems that are very popular with mainstream growers today. Likewise, brands such as Hortilux bulbs and Value Brite hoods offer more budget oriented brands.

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Light Emitting Diode (LED) systems are gaining rapid popularity because of their low heat generation and high energy efficiency. The technology surrounding LED is also increasing, making them very viable for small indoor gardens as their price continues to drop. Some of the top selling LED brands include; Advanced Platinum, GalaxyHydro, Kind LED, Apollo Horticulture and King.

How long to leave the lights on

Some growers prefer to use a 24-hour light cycle for vegetative growth, others tend to leave the lights on about at least 16 – 18 hours. Regardless of what light cycle you use, just make sure that you have over 12 hours of light on your plants or their hormones will begin to trigger the flowering phase.

Ideal temperatures and humidity for cannabis growth

The temperature for outdoor growth should ideally range from a low of about 55 F to a high of about 85F. Early spring and late fall you can expect to see the low’s possibly dropping below 55F, while in mid-summer highs may exceed 85F. Fluctuations in temperature are okay, as long as they are not for extended periods. Methods to keep those ideal temperatures consistent throughout your growing season include plant blankets for cool nights and shade cloth for hot days.

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Speaking of outdoor variables, excessive wind can damage your plants while excessive moisture can encourage the growth of molds and mildews. So stake your seedlings to support them in the wind and make sure soil has good drainage.

Indoors, ideally, the temp should be maintained at 65F to 85F with a difference of no more than 20 degrees. Humidity for marijuana plants should be about 60% in the vegetative growth cycle.

Feeding your growing cannabis plant

Start adding nutrients to your watering routine now. Follow the directions of the products you are using, adding the nutrients conservatively as per the label, building up to the maximum dosage over time. Be careful not to overwater your plant and avoid combining so many nutrients that the plant loses its ability to uptake the additives. Generally, in the soil mix above, I use some calcium and magnesium, some seaweed extract, and a good vegetative plant growth mix specialized for marijuana growing. Botanicare, Advance Nutrients and Fox Farms are all reputable nutrient companies.

Your plant will tell you whether or not you are treating it right by rewarding you with rapid growth in both height and new lush green foliage. On the other hand, too much or not enough water, or, too much or not enough fertilizer, and the plant will droop and begin to yellow or brown at the leaves. Keep your eyes open for any symptoms and make changes in your routine to correct any water or nutrient imbalance. Have fun, don’t try too hard, and let the plant do what it does best – grow!

GreenState cultivation columnist Kevin Oliver is the co-author of “Idiot’s Guides: Growing Marijuana” (Alpha, 2016). Besides being founder/CSO of Washington’s Finest Cannabis and sitting on the Board of Directors for NORML, Oliver is also the executive director of WANORML/WANORML PAC — the Washington Affiliate of the National Organization for the Reform of Marijuana Laws.