The Soil Requirements for Canadian Hemlock

Canadian hemlock, known scientifically as Tsuga canadensis, is an evergreen tree that typically grows between 30 and 60 feet tall. Under the appropriate conditions this tree naturally grows in an attractive, symmetrical and conical shape, or it can be trained into a screen, hedge or shade plant. Proper soil texture, pH and drainage can help to ensure that a Canadian hemlock will reach its full potential.

Soil Type

The Canadian hemlock prefers a loam or sandy loam soil. The primary concern in a sandy soil is the inability of the soil to retain moisture. To address this, prepare the soil prior to planting by adding ample humus to a deep, wide planting hole and mulch around the tree regularly. Additionally, Canadian hemlock has a low salt tolerance, so it may not be suitable for areas with a high salt content.

Soil pH

The Canadian hemlock prefers a cool, moist soil with a pH between 5 and 6.5. However, it may be capable of growing in a much broader pH range. If the soil is extremely acidic or alkaline, consider amending the soil around the hemlock to create a more hospitable environment.

Drainage and Moisture

The Canadian hemlock prefers moist, well-drained sites, but can grow in somewhat dry or moist, acidic soil. The hemlock may suffer root rot and bark splitting if the growing site is always wet. If irrigation is not managed properly immediately following transplanting, the tree will suffer from some degree of dieback. The tree grows well in a large, mulched bed where soil remains cool and only partial sun is permitted. Canadian hemlock grown in full sun requires consistent and frequent watering.

Tolerance of Black Walnut

Interestingly, Canadian hemlock is one of only a few tree species that has been observed growing under or near black walnut trees. Black walnut roots produce a substance known as juglone, which is toxic to many plants. However, Canadian hemlock may tolerate this toxin.

Weeping Canadian Hemlock

The weeping Canadian hemlock, or Tsuga canadensis Sargentii, has little hint of the regular Canadian hemlock's strong conical shape and instead has soft green needles attached to drooping branches that can touch the ground. It typically grows twice as wide as its height. This type of tree prefers a moist, well-drained site but can grow in moderately dry to moist acidic soil. If a site is constantly wet, the weeping Canadian hemlock may suffer from bark split or root rot.

References

• New England Gardener's Guide; Jacqueline Hériteau and Holly Hunter Stonehill; 2003
• University of Florida IFAS Extension; Tsuga canadensis: Canadian Hemlock; Edward F. Gilman and Dennis G. Watson; December 2006
• Virginia Cooperative Extension; Canadian Hemlock, Tsuga canadensis; Alex X. Niemiera; November 03, 2010
• University of Florida IFAS Extension; Tsuga canadensis 'Sargentii': Weeping Canadian Hemlock; Edward F. Gilman and Dennis G. Watson; December 2006