Conifers are evergreen trees with needle-like or scalelike foliage and cones in shades of red, blue or brown. Conifers also come in dwarf sizes that are widely used as container plants, in rock gardens and Japanese gardens and as background for bedding plants. Conifers have a slow growth rate and grow best in a certain type of potting soil.
Dwarf conifers that are grown in containers and confined spaces do not exceed a mature height of 2 to 3 feet. Use five parts of an all-purpose potting soil mixed with one part pea gravel for growing conifers, suggest Sean Conway and Lee Alan Buttala in "Sean Conway's Cultivating Life." Conifers require a very well-drained soil for healthy growth, and pea gravel helps to improve drainage. Repot plants when they outgrow their original containers.
Reasons for Dwarf Size
Dwarf conifers occur as a result of bud or seedling mutation caused by genetic differences where these seedlings or buds differ in growth from the parent plant. Bushy offshoots with multiple branches growing from the tree frequently develop into dwarf-sized, compact plants. According to the American Conifer Society, dwarf conifers have a growth rate of 3 to 6 inches annually.
Dwarf conifers prefer areas of full sun, except larch, hemlock and false cypress, which adapt well to areas of light shade as well. If you're planting conifers in the ground, make sure the soil is well-drained, or plant on a raised bed in poorly drained sites. Amend the planting area with compost, perlite or peat in poor-quality soils. Avoid excessive soil enrichment, as this tends to reduce the dwarf characteristics of the conifer.
Use very minimal amounts of fertiliser, as the plants will outgrow their miniature status in overly rich soil. The recommended rate is approximately 1 tbsp of a 5-10-10 fertiliser mixed into the soil at planting time, as cited by the University of Washington Extension. Organic fertiliser choices include 3-15-0 bonemeal or 7-2-1 cottonseed meal. Conifers grow best in a soil pH of 4.5 to 6.0. Low acidic levels are indicted by chlorosis, or yellowing foliage.