Evergreen Trees

Agriculture at Colorado State University Cooperative Extensioin

no. 7.403

Evergreen Trees

by R.A. Cox and J.E. Klett¹

Quick Facts...

Most evergreens prefer full sun; some will tolerate partial shade.
In selecting evergreens, consider space, soil and site conditions, and weather factors.
Evergreens have different water preferences. Group drought-tolerant types separately from those that require more water.
All evergreens benefit from mulches. All need sufficient water to become established after transplanting. This varies with species, soil conditions, weather and site conditions.
Most evergreens benefit from supplemental water during dry, warm or windy periods from November to March.

Narrowleaf evergreen (conifer) trees give a landscape year-round interest, color and texture. Conifer trees are versatile and can be used as specimens, hedges, privacy screens, backdrops for smaller flowering plants, or as a windbreak planted on the north and west to deflect or intercept winter winds. (See fact sheet 7.225, Landscaping for Energy Conservation.)

"Evergreen" refers to trees that normally retain most of their foliage (needles) through the winter. Such trees, however, do not retain all of their needles indefinitely. For example, ponderosa pine drops needles each year that are three to five years old. These older needles are the innermost ones toward the main trunk. Younger needles, further out on the branch, are retained until they are three to five years old. This annual browning and drop of innermost, older needles can cause concern, but it is a natural process. Other evergreens may have needle lifespans of two to 17 years, depending on the species.

Selection

Examine the intended planting space for good soil drainage, adequate sunlight and sufficient space to accommodate the desired evergreen tree at its mature size. Allow for clear access to driveways, sidewalks and entryways. Determine whether the tree's growth will affect any overhead utility lines.

In smaller sites, consider smaller trees or shrubs. (See 7.418, Small Deciduous Trees; 7.414, Evergreen Shrubs; or 7.415, Deciduous Shrubs.) Consider dwarf conifers for limited space areas.

Planting

Before planting, call the utility companies to mark the location of any underground lines to avoid damaging them while digging. Prepare soil before planting by adding organic materials (sphagnum peat moss, aged manure, shredded leaves or compost) in a 1- to 3-inch thick layer over the planting area.

Extend the planting area for several feet in all directions from the actual planting spot. Spade or rototill the organic materials into the soil and mix well 10 to 12 inches deep before planting. If there is sufficient space, use several kinds of evergreens to add variety to the landscape.

Watering and Maintenance

The following list indicates the relative moisture needs of evergreens. Plant species with similar water needs in the same general area -- do not mix trees with widely different water needs.

Evergreens that need less moisture may work well on slopes. All evergreens usable in Colorado prefer well-drained soils. Avoid planting them in swales or poorly-drained, soggy areas. Evergreens that need less moisture may not do well in lawn areas because of the amount of water needed to sustain the lawn. Even for those trees that need more moisture and are compatible with lawn watering, leave the planting area free of sod to allow for good root development. Sod roots compete with tree roots for air, nutrients and water in the soil. An organic mulch is recommended over the entire planting area. (See 7.214, Mulches for Home Grounds.)

Most evergreens growing in Colorado landscapes, whether recently transplanted or well-established, benefit from supplemental water during winter dry spells. Often, such spells are characterized by drying winds or unseasonably warm temperatures, further emphasizing the need for watering. (See 7.211, Fall and Winter Watering, and 7.833, The Science of Planting Trees.)

For gardeners above 6,000 feet, some of the plants listed are not adaptable. Refer to 7.423, Trees and Shrubs for Mountain Areas for specific recommendations. Refer to 7.421, Native Trees for Colorado Landscapes and 7.422, Native Shrubs for Colorado Landscapes for native evergreens.

Plant Name	Mature Size (H x W)	Tree Shape	Growth Rate¹	Soil Moisture ²	Comments and Cultural Hints
Table 1: Recommended evergreen trees for Colorado.
Arborvitae
Thuja occidentalis Eastern or American arborvitae 'Smaragd' (Emerald) 'Techny'	20' x 10' 12' x 4' 12' x 8'	conical columnar broadly columnar	s s s	H H H	Prefers higher humidity; all varieties listed below are subject to winterburn and snow damage. Dense, medium green foliage. Better cold tolerance; dark green foliage.
Fir
Abies concolor* White fir 'Candicans'	60' x 20' 12' x 8'	conical narrowly columnar	m m	M-H M-H	Flat, blue-green needles; may winterburn in windy sites; may perform poorly in clay soils. Longer, silvery-blue needles.
Abies koreana ‘Hortsmann’s Silberlocke’	15' x 12'	broadly conical	s	M-H	Needles curved upright exposing silvery undersides, violet purple cones.
Abies lasiocarpa* ‘Glauca Compacta’ Blue Dwarf Rocky Mountain fir	15' x 9'	broadly conical	s	M-H	Slower growing with silver-blue foliage.
Pseudotsuga menziesii* Douglas-fir	60' x 20'	conical	m-f	M	Unique cones with "mouse-tail" bracts; more cold-tolerant and soil-adaptable.
Juniper
Juniperus chinensis Chinese juniper ‘Blue Point’ 'Robusta Green' 'Spartan' ‘Spearmint’	12' x 18' 12' x 12' 12' x 5' 15’ x 6’	broadly columnar broadly columnar conical conical	m m m-f m	L L L L	Slower growing with silver-blue foliage, blue-green fruit. Abundant fruit; growth habit can be irregular Dense green foliage. Dense, bright green foliage.
Juniperus scopulorum* Rocky Mountain juniper 'Cologreen' 'Grey Gleam' 'Moonglow' 'Skyrocket' ‘Tolleson’s Weeping’ 'Welchii' 'Wichita Blue'	variable 15' x 8' 12' x 6' 15' x 8' 12' x 3' 18' x 10' 10' x 15' 12' x 6'	broadly columnar broadly columnar conical broadly columnar narrowly columnar weeping broadly columnar broadly columnar	s-m s-m s s-m s-m s-m s-m s-m	L L L L L L L L	Foliage color varies from green to blue-green. Dense, green foliage; abundant fruit. No fruit; dense, gray foliage. Dense, silver-blue foliage. Narrow; subject to snow damage; formerly listed as J. virginiana 'Skyrocket'. Weeping branches with silvery-blue foliage. Blue-green to medium green foliage. Bright blue foliage color.
Juniperus virginiana Eastern redcedar 'Canaertii' 'Hillspire,' ('Cupressifolia') 'Manhattan Blue'	40' x 15' 20' x 10' 15' x 6' 20' x 15'	conical conical conical broadly columnar	s-m s-m s-m s-m	L L L L	Open, horizontal branching; foliage turns brownish in winter. Abundant whitish-blue fruit contrasts with green foliage. Columnar; bright green foliage. Foliage blue-green, turning medium green in winter; open growth habit.
Larch
Larix decidua European Larch	45' x 18'	broadly columnar	m	M-H	A deciduous conifer. Needles in clusters that turn yellow in fall before dropping.
Pine
Pinus aristata* Bristlecone pine	20' x 15'	irregular	s	L-M	Shorter, dark green needles with white resin dots; specimen plant.
Pinus edulis* Pinyon pine	20' x 15'	conical to rounded	s-m	L	Not suited for frequently watered lawn areas; edible seeds may not develop dependably in urban landscapes.
Pinus flexilis* Limber pine ‘Vanderwolf’s Pyramid’	40' x 20' 25' x 10'	broadly columnar conical	m m	L-M L-M	Wind-tolerant; adaptable to dry soils; very flexible branches; needles about 2". Blue-green needles with ascending branches.
Pinus heldreichii var leucodermis Bosnian Pine	18' x 10'	broadly columnar	m	L-M	Stiff, dark green needles in brush-like tufts.
Pinus mugo Mugo pine ‘Tannenbaum’	variable 12' x 6'	irregular broadly columnar	m s	L-M L-M	Variable growth habit; tree-like to shrubby; dwarf forms commonly sold for landscapes. Good winter color and hardiness.
Pinus nigra Austrian pine Arnold Sentinel’ ‘Teardrop’	50' x 25' 15' x 5' 15' x 5'	broadly columnar narrowly columnar narrowly columnar	m s s	L-M L-M L-M	3-5", dark green needles; tolerates many soil types and urban pollution. Dense, dark green needles. Dense, medium green needles.
Pinus ponderosa* Ponderosa pine	60' x 25'	broadly columnar	m	L	Longer, yellow-green needles; older trees develop cinnamon-brown bark.
Pinus strobiformis* Southwestern white pine	40' x 20'	broadly columnar	m-f	L-M	Blue-green needles; similar to limber pine; attractive elongated cones.
Pinus strobus Eastern white pine ‘Fastigiata’ ‘Pendula’	50' x 20' 35' x 12' 14' x 8'	broadly columnar narrowly columnar weeping	m-f m m	M M M	Horizontal branching; fine-textured, blue-green needles; best in protected sites. Fine textured blue-green needles. Bluish-green needles on long branches that sweep the ground.
Pinus sylvestris Scotch pine ‘Fastigiata’	40' x 25' 15' x 5'	broadly columnar narrowly columnar	m m	M M	Sharp, blue-green, twisted needles; mature bark is orange-brown. Tightly angled branches often damaged by snow storms.
Spruce
Picea abies Norway spruce ‘Cupressina’	50' x 25' 15' x 5'	broadly columnar narrowly columnar	m-f m-f	M-H M-H	Short green needles; branches droop with age. Good vertical acent; withstands snowloads.
Picea glauca White spruce	50' x 20'	broadly columnar	m	M	Short, greenish-white needles; adaptable tree.
Picea glauca var densata Black Hills spruce	30' x 15'	conical	s	M	Dense, short foliage, dark green needles.
Picea pungens* Colorado spruce	60' x 25'	broadly columnar	m	M-H	Needles short, sharp, green to blue-green.
Picea pungens glauca* Colorado blue spruce ‘Baby Blue Eyes’ ‘Bakeri’ 'Hoopsii' ‘Fat Albert’ ‘Iseli Fastigiate’ ‘R.H. Montgomery’ (‘Montgomery’)	60' x 25' 15' x 8' 30' x 15' 45' x 15' 30' x 20' 15' x 5' 12' x 8'	broadly columnar broadly columnar broadly columnar broadly columnar broadly pyramidal narrowly columnar broadly pyramidal	m s s m s s s	M-H M-H M-H H M-H M-H M-H	Needles short, sharp, blue; several varieties selected for blue needles. Colorado state tree. Lighter blue needles, dense growth habit. Brilliant blue needles and slightly irregular branching. Intense silver-blue needles. Outstanding blue-needled form with strong central leader. Striking blue needles. Striking silver-blue needles.
¹Growth rate: s = slow; m = moderate; f = fast ²Soil moisture: H = high; M = medium; L = low * Native to Colorado

¹R.A. Cox, Colorado State University Extension horticulture agent, Jefferson County; and J.E. Klett, Extension landscape horticulturist and professor; horticulture and landscape architecture. Revised 4/05.

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