Trees in Raised Planters

Creating Raised Planters

• Before constructing a raised tree planter, cover the site with black plastic or heavy mulch for at least one month to kill any plants and prevent weed growth. Construct the sides of the planter with stone, brick or wood that's rot resistant, non-creosote or pentachlorophenol treated. Frames should be at least 6 inches tall to accommodate soil and roots and no more than 3 or 4 feet wide to allow for ease of access. Fill planters with a nutrient-rich mixture of one part organic peat moss, decomposed manure or compost one part sand or perlite and two parts soil. Such mixtures tend to be acidic, so test the soil and add limestone to raise pH levels. Mulch planted trees with organic mulch or surround with landscape fabric covered with wood chips to prevent weed growth and conserve moisture

Evergreen Trees

• Evergreen trees keep their foliage all year, making them appropriate choices for raised beds. A planter-tolerant evergreen is the Filifera falsecypress, an 8-foot-tall tree with weeping branches that are covered with green-silver foliage. This broad-leaved evergreen has dark foliage and produces white summer blossoms. For large raised planters, choose the umbraculifera Japanese red pine, a 10-foot-tall cultivar that has orange bark and a twisting trunk. Other evergreens for raised planters include the Nelle R. Stevens holly, junipers, mugo pine, Swiss stone pine and lacebark pine.

Deciduous Trees

• Several small maples grow well in planters. These deciduous trees have palmate foliage and attractive fall color. The trident maple grows to 35 feet tall and tolerates, wind, salt, air pollution and poor, compacted or dry soil. The amur maple grows slowly to 20 feet tall. It tolerates wind and drought and resists pests. For large planters, the sunburst honeylocust grows to 35 feet tall. It has yellow new growth that ages to bright green.

Considerations

• Raised planters require regular fertilization and irrigation, just like an in-ground planting bed. Use a slow-release fertilizer with micronutrients or an organic- or manure-based fertilizer at least annually. Avoid overhead irrigation systems as they create wet foliage, which can lead to diseases. Instead, use a soaker hose or a drip system. When choosing trees for a raised planter, select varieties that can survive in a confined space -- such as dwarf, semi-dwarf cultivars or small species -- and that can tolerate extreme temperatures, as soil in raised planters tends to experience cooler or warmer temperatures than ground soil.
  .