Broadleaf evergreen shrubs, like Japanese andromeda, are vulnerable in times of temperature extremes and more so if they are in containers. The container means that the roots of the plant are closer to the surface and less insulated than they would be in the ground. In winter, even plants that would be hardy in our area may find the additional cold they experience at the root too challenging. They will also warm more quickly in a period of mild winter temperature, so the whipsaw is greater. Summer heat will more directly affect the plant's roots.

Begin by choosing a plant that is well-sized for container growth and a container that allows adequate room for the root system of the plant with a margin of soil to insulate it. Remember that dark containers will heat up and expose your plant's roots to greater heat fluctuations in winter sun and heat extremes in the summer. 

In all other matters, care for evergreen shrubs in containers as you would those planted in the ground.  Water them well in the late fall so that they are in top condition when the temperature drops. Once the soil has frozen, mulch the top of the container, but do not allow the mulch to creep up the stem of the plant or clump under the leaves where it can harbor disease. Do not mulch deeply or the roots can be starved of air and water. Be mindful of water needs in the summer. The more protected the location of the container (protected by building structure, awning, other plants), the less likely you are to need an extra barriers to protect container-planted shrubs in winter.

For more information, and help with choosing a dwarf plant for a container, see our Guide to Japanese Andromeda.

Courtesy of NYBG Plant Information Service.