Among the many menial tasks performed in the nursery that I don’t miss is ‘spacing’. As the rhododendrons mature, they must be moved away from each other to maximize sun exposure and allow new growth to extend in all directions. Otherwise, growth is too crowded and only extends upward.

Newly canned rhododendrons are initially placed ‘can to can’ to conserve space, but also to protect the cans from direct sun exposure. (The black vinyl containers that nursery stock is grown and marketed in are known as cans; not pots.) As they grow, they may be spaced into areas left vacant by more mature rhododendrons that have already been marketed. Spacing accommodates expanding growth, but does not adversely expose the cans below. The most mature specimens are eventually able to shade their own cans even if moved away from others.

Shading the cans from direct sun exposure is necessary because the black vinyl that the cans are composed of can become detrimentally warm if exposed to sunlight too long. Roots inside are easily cooked if the soil becomes too hot. Even if the soil is not hot enough to cook roots, increased temperatures promote the  proliferation of many fungal rot organisms.

Likewise, other plants purchased in nurseries should not be expected to perform in the cans they were grown in unless the cans are protected from sun exposure. Those unable to shade their own cans and are not immediately installed into the garden should be placed in an area where the can is shaded, but sun exposure to the foliar canopy is sufficient. Placing recently acquired nursery stock on the north side of a fence or building provides adequate shade to the cans, and allows enough sunlight, even if only ambient light, to sustain the stock until installation. Most nursery stock will tolerate considerable shade for at least a few days.

Specimens may be left in their nursery cans if the cans are placed into larger pots or containers, or nestled into shallow shrubbery or deep ground-cover. Containers and pots in which plants are grown in around the home should not exhibit the same uncomfortable characteristics of the nursery cans.

Although clay pots are heavy and fragile, and wood containers eventually rot, they are preferred materials holding plants. Both are well insulated and porous, retaining slight moisture as contained soil dries. Lightly colored plastic does not collect as much heat as black vinyl, but is not as well insulated or porous as wood or clay.

All containers require drainage. Pots or urns without drainage holes are only useful for containing other pots or nursery cans if the inner containers are elevated above water which drains from them if any accumulates.

Drainage pans, trays or dishes as well as undrained outer pots or urns that collect water that drains from containers should not hold stagnate water long enough for mosquitoes to breed. A constant presence of water is also an indication that irrigation is too generous. Of course, containment of drained water is not necessary for containers on soil or concrete if stains are not a concern.

Regardless of proper containment of drainage water, rot may become a problem under containers on wooden surfaces, such as decks and porches, even if the surface is tiled or painted. Slight elevation of the containers allows the surface below to dry, inhibiting rot. This may be accomplished with the use of platforms with wheels or clay pot ‘feet’.

Unfortunately, most mixed potting soil contains a very generous proportion of peat moss which decomposes and causes potted plants to settle. As this happens, new soil should not be added to the top of the root system. Instead, the pot should be ‘stuffed’. This involves removing the plant, adding new soil to the container, replacing the plant and adding soil around it to compensate for the wider diameter of the pot higher up.