Best Soil for Conifers

By Susan Eyre

Learn how to provide the best foundation for your conifer planting and growth.

The conifer, Norway Spruce (Picea abies ‘Cupressina’) in clay-loam
The conifer, Norway Spruce (Picea abies ‘Cupressina’) in clay-loam

Siting plants on an inclined plane or irregular rolling slope adds interest to a flat surface and provides the opportunity to stage dwarf plants toward the foreground. Large or intermediate conifers can be used to block unwanted sightlines. Color, texture, form, seasonal changes, bark, and coning attributes provide great options.

Whatever landscape situation exists, there is a superlative conifer available for that site. Basic knowledge of conifers and of the site is required to make wise plant choices.

Considering Soil Foundation Types for Conifers

Before planting conifers, you must be able to answer this critical question: What is the drainage and percolation of the site? Most conifers thrive in well-drained sandy, clay loam in full sun. Not all projects have ideal conditions, but good drainage is essential to guarantee the success of most plantings.

Test your soil percolation by digging a hole 2’ deep with a post hole digger. Fill the hole with water, let it drain and fill again. If the hole does not drain in two hours after the second filling, the soil is limited for conifers. In heavy clay, raise at least half the root ball out of the clay layer and surround the protruding half with good topsoil.

Another solution is to remove narrow channels of clay leading away from the plant, like spokes of a wheel. Replace that soil with sand or pea gravel so that water and rootlets have an easy path. Water must drain away easily, or the roots will rot due to lack of oxygen.

The conifer, Japanese red pine (Pinus densiflora ‘Pendula’) in clay soil
The conifer, Japanese red pine (Pinus densiflora ‘Pendula’) in clay soil

Matching Conifers with Soil Types

If your soil is heavy and wet and can’t be amended, there are some conifers which are naturally predisposed to such conditions. Choose Larix (larch), Taxodium (bald cypress), Metasequoia (dawn redwood), or Thuja (arborvitae). Taxodium distichum is one of the most versatile conifers because it can thrive in standing water or on a rocky ridge. It is the most adaptable to heavy clay soils.

Taxus (yew), Pinus (pine), Picea (spruce) and Abies (fir) demand good drainage and will die with too much water in the soil. Provide your trees with good soil, amendments, and sufficient water. Extra watering is needed during drought periods and until the ground freezes.

Soil Ammendments for Conifers

Mulch is a positive thing to maintain soil moisture, but it should not be placed too close to the trunk. Chunk bark or coarse wood chips can be beneficial for firs (which prefer an eastern exposure). Pine needles, coarse pine fines or 2” wood chips work well for other conifers. Use a light application of compost, peat moss or worm castings and sulfur in reasonable doses for these acid-loving plants.

Photographs by Susan Eyre.

This article was originally published in the Fall 2014 issue of Conifer Quarterly. Join the American Conifer Society to access our extensive library of conifer-related articles and connect to a nationwide group of plant lovers! Become a member for only $40 a year and get discounts with our growing list of participating nurseries in our Nursery Discount Program.

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