Hemlocks (Tsuga canadensis) are among North America's most gracefully cone-bearing trees. Becoming magnificent landscape specimens or nice in a row as a hedge or screen, their growth and beauty depends on their growing conditions, particularly soil. The best soil for hemlock is an organic-rich loam that is acidic and is consistently moist. The soil should drain well, never becoming soggy or flooded.
Soil and Composition
In its native habitats, the hemlock grows on loams and sands that may have layers of fertile silt or incorporated gravel. Organic matter, such as decaying conifer needles, is a key component to making optimal growing conditions. Heavy clay soil must be made more porous with the use of mulch and compost. Soil should not be hard and compacted.
Hemlock grows in highly acidic to near-neutral pH soil, corresponding to pH readings of 4.0 (highly acidic) to 7.2 (near neutral). Alkaline soils, those above a pH of 7.2 are not ideal because they will inhibit intake of vital nutrients.
Moisture and Drainage
Soil must range from barely dry to very wet, but always have good drainage. The finest plant growth occurs on consistently moist soils that never flood or are soggy throughout the year. Water should soak fully into the soil within 5 to 10 minutes after a rainfall. Slightly drier soils are only good in climates that are cool in summer.