Black Hills Spruce (Picea glauca var. densata)

The Black Hills spruce tree (Picea glauca var. densata) is a cultivar of white spruce that grows high in the Black Hills of South Dakota and is known for its aromatic deep green to blue-green needles and dense, narrow form in the landscape. The Black Hills spruce grows best in dry, non-humid conditions with cold winters and cool summers, but the tree requires full sunlight and acidic soil. Be aware that this tree will only do well in USDA hardiness zones 3-6.

I. Appearance and Characteristics

A large evergreen tree with a central trunk and dense, ascending, lateral branches from the ground up that form a broad pyramidal to conical crown. It varies from the typical white spruce in its denser, more compact habit and slower growth rate. It has a shallow, fibrous, wide spreading root system. The thin bark is ashy gray or brown, shallowly fissured and separated into thin flaky scales. The needles are individually attached, and foliage color varies from deep green to blue green. The brown cylindrical cones appear in late July and may persist on the tree into January.

The Black Hills spruce grows to a height of 30–60′ and a spread of 15–25′ at maturity.

II. How to Grow and Care

Sunlight

The Black Hills spruce will grow in partial shade for those with less ideal light conditions. It does prefer full sun, though, and you will see slower growth if you plant your tree in anything less than six to eight hours of sun.

Temperature and Humidity

This particular cultivar of white spruce lives in the Black Hills of South Dakota at elevations higher than 6,000 feet. Because of this, it has adapted to dry conditions, cold winters, and cool summers. When placing it at lower elevations, be sure to plant it in a location that leaves ample room for airflow to allow the wind to dry moisture from its branches.

Watering

Once your tree is established, it won’t need much supplemental watering, but until then, you will need to water it weekly during periods without heavy rains. Continue this for the first two years, and your tree will be one step closer to establishing a well-watered, healthy root system.

Soil

For those looking for a particularly adaptable tree for soil conditions, the Black Hills spruce might be the tree for you. It can do well in well-draining clay, loam, and sand. While it can handle some alkalinity, your tree will favor slightly acidic soil. You can always test this using a simple pH test and amend the soil as needed.

Fertilizing

There is no real need to give this tree supplemental fertilizer. When refilling the hole you dug to plant your spruce, add good organic compost to the back-fill. If you should notice any signs that your tree is suffering, test the soil and check if deficiencies can be corrected by adding nutrients as needed.

Pruning

Prune dead or broken branches at any time. You also can raise the canopy by removing drooping, lower branches at the trunk. Do any optional pruning in late winter or early spring. Otherwise, the tree will not need regular pruning.

Propagation

Propagate Black Hills spruce trees by seed or cutting, just as you would any white spruce tree. Take these steps if you choose to do cuttings in the late summer or early fall:

• Using a sterilized cutting tool, clip off a healthy 6- to 8-inch shoot.
• Angle the base of the cutting with another cut using a sterilized tool.
• Remove all the needles from the lower portion of the cutting, leaving the top 1/3 section of needles in place.
• Dip the angled end of the cutting in rooting hormone, though this is an optional step.
• Plant the cutting directly into moist soil in a sunny spot outdoors and keep moist.

How to Grow From Seed

Growing a spruce tree from seed takes patience because you need to let the roots mature a bit before planting outdoors. However, there will be an abundance of seeds in the cones produced by this spruce tree so you can plant a stand of them if you desire. Black Hills spruce tree’s cones are small, about the size of a large thumb.1

• Watch for fallen cones in the fall and let them dry thoroughly. They will open on their own and you can collect the seeds.
• Place the seeds in a plastic bag and put them in the refrigerator for three weeks.
• Remove the seeds and soak them in water for 24 hours. Use seeds that sink and discard seeds that float to the top because they are not viable.
• Plant seeds in a small pot filled with rich soil.
• Cover the seeds and keep the soil moist, but never soaked.
• Place pots in a protected area outdoors in the late spring.
• Seeds will typically germinate in three weeks.
• Keep a seedling in a pot for at least a season to let the root system grow and then you can plant it in the ground.

Pests and Diseases

Common Pests & Plant Diseases

Mites, aphids, and bagworms are the most common pests with the Black Hills spruce, though none should be able to do enough damage to a healthy tree to kill it. Bagworms are the most obvious pest and can be unsightly. Remove those within reach by hand and treat the tree with Bacillus thuringiensis.

The only diseases that may cause you the rare issue are various rusts. One occurrence of rust will not likely be of concern. A common sign is the yellowing and dropping of infected needles.

Common Problems

The Black Hills spruce does not have many issues unless it’s placed in an unsuitable environment. Note that the tree does not like urban or coastal environments due to humidity, overcast, or wet conditions.

III. Uses and Benefits

• Ornamental uses

Black Hills spruce is a great choice to blend into a windbreak with other tree species. It is slower growing, but will give you a dense, sturdy tree to withstand strong winds and storms better than faster growing evergreens.

It also makes a good specimen tree for landscapes because it is so dense and has a deeper green color than blue spruce.

• Other uses

Black Hills spruce has good wood for lumber and makes a great Christmas tree. It is also good for wildlife as it is browsed by mammals. It provides great nesting sites for birds and good winter cover for many animals. It can also be used as a source of pulp to make paper.