Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible

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    Step Nine: Fertilize soilless mixes after transplanting with a complete hydroponic fertilizer that contains soluble chelated nutrients. New potting soil usually supplies enough nutrients for a couple of weeks before supplemental fertilization is necessary.

This clone grew in a four-inch (10-cm) pot and is ready to be transplanted.
    Step Ten: Minimum Container Size chart below.
     
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    Seedlings and clones can also be transplanted directly into a three- to five-gallon (11-19 L) pot, a system which requires fewer containers and involves less work and less possible plant stress. The larger volume of soil holds water and nutrients longer and requires less frequent watering. When clones and seedlings are transplanted directly into a five-gallon (19 L) container, the roots grow down, out, and around the container walls and bottom. In fact, the majority of roots grow out of the soil and form a layer behind the container wall.
    To encourage roots to develop a dense compact system, transplant just before they have outgrown their container. Transplanting a well-rooted clone in a root cube into a four-inch (10-cm) pot and transplanting the four-inch (10-cm) pot into a three-gallon (11 L) pot or grow bag causes roots to develop a more extensive system in a small ball of growing medium. Successful transplanting causes minimal stress. Most marijuana crops are in the ground for such a short time that bungled transplanting costs valuable recuperation time and loss in production.
    Transplant clones and seedlings into raised beds and large planter boxes directly from four-inch (10-cm) pots. As many as 20 plants can be transplanted into a 24 × 24 × 12-inch (61 × 61 × 30 cm) planter, but six to twelve plants will yield about the same dry weight of buds. Once plants start crowding and shading one another, bend stems outward and tie them to a trellis attached to the planter. Large planters require less maintenance. The larger mass of soil retains water and nutrients much longer and more evenly. One downside is that all plants must receive the same water and diet.

This clone was transplanted directly into a large container at the Cannabis College in Amsterdam.
    Three-gallon (11 L) containers are the ideal size for two- to three-foot-tall (60-90 cm) plants. Larger pots are usually unnecessary because plants grow no longer than a week or two in the vegetative stage and six to ten weeks flowering. Smaller three-gallon (11 L) pots are easy to move and handle. Roots also grow less during flowering. By the time a plant is potbound, it is ready to harvest. I used to recommend up to a five-gallon (19 L) container for plants that are harvested after 90 total days of life. I now believe this is a waste. While the smaller containers require daily watering, they produce harvests comparable to those of five-gallon (19 L) containers.
     
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Hardening-off
    Hardening-off is the process of toughening-up clones and seedlings. During the rooting process, leaves supplied much of the moisture for the clone. Now, healthy white new roots are supplying moisture to the clone. Check for root damage. Brown roots are rotting and lack oxygen. Thin hair-like dark roots are dried out. Once damaged, roots remain damaged. New roots must grow to replace damaged roots. Cull out any clones with damaged roots, because they will grow slowly. The protective wax coating must also grow back on leaves. It is best to acclimate rooted clones to the grow room over the course of a week. Gradually hardening-off clones will assure they suffer a minimum of stress and continue to grow rapidly.
    Harden off the strong ones, and introduce them to the real world–the grow room where they will see photosyntheti-cally active response (PAR) at full value and nutrients that make their cells quiver. Now is the time to pre-grow clones before placing them into the flowering room.
    Foliage loses its protective wax coating when it is pampered during cloning, so it is very tender now. New roots must start to transport water via the stems to the leaves.

These beautiful little seedlings were started indoors under a fluorescent lamp. The grower moves them outdoors for a few hours every day to harden-off and acclimate to the outdoor environment.
    The roots and moisture-transport system start to work on strong, healthy clones first. Clones that lag behind now should be tossed out, because they will always be slow. You can let them root longer and not transplant them until