Superior Woody Plants

Currently there are about 1100 different taxa of woody plants being evaluated in the arboretum area at the W. D. Holley Plant Environmental Research Center (PERC) on the Colorado State University campus. The woody plants are evaluated yearly for growth rate, hardiness, growth habit, foliage characteristics, flower & fruit characteristics, disease and insect resistance and other landscape features. Listed below are some plants that merit more attention for use in the Rocky Mountain/High Plains Area. You are welcome to visit PERC located in the south-west corner of Colorado State University in Fort Collins any day of the year during daylight hours.

Buxus microphylla koreana ‘Julia Jane’
(Julia Jane Boxwood)

Growth Habit – dense, rounded
Height: 3-4′
Spread: 3-4′
Flowers – April, not showy but fragrant, attracts bees
Foliage – Broadleaf, evergreen
Hardiness Zone – 5
Cultural Requirements – Requires full or partial sun, moderate moisture, well-drained soils, mulch and winter watering is helpful.
Comments – Boxwoods generally are best in protected spots out of winter winds but ‘Julia Jane’ is less prone to “winterburn” and keeps a good dark green color through the winter.

Rosa x ‘Meizmea’
(Carefree Spirit Rose)

Growth Habit – Mounding bush
Height: 3-5 ft.
Spread: 3-5 ft.
Flowers – Deep cherry red blossoms maturing to pink with white eyes, flowering is continous
Foliage – Very attractive dark green and glossy, vigorous
Hardiness Zone – 5
Cultural Requirements – Sun, moderate water
Comments – Selected in 2009 as an AARS winner. Noted as the first and only landscape shrub to date to prevail despite not using fungicides. Hybridized by Jacques Mouchotte, director of research at Meilland International and introduced by Conard-Pyle Co. of West Grove, Penn

Sambucus pubins
(Red Elderberry)

Growth Habit – Upright, irregular
Height: 9-12 ft.
Spread: 8-15 ft.
Foliage – Dark green
Flowers – White/yellow
Hardiness Zone – 3
Cultural Requirements – Does best in moist soils although will tolerate dry soils, adaptable to acid or alkaline conditions, does sucker some
Comments – Flowers are interesting close up and produce attractive scarlet fruit in late June to early July. Fruit is showy and good for attracting wildlife. Attractive as a background shrub. The cultivar ‘Dissecta’ has deeply divided leaflets that adds a more delicate appearance. Obtained from American Horticultural Society in 1987.

Tilia cordata ‘Corzam’
(Corinthian® Linden)

Growth Habit – Pyramidal
Height: 10-15 ft.
Spread: 8-12 ft.
Flowers – Yellowish and provides interest but not very showy, fragrant
Foliage – Medium to dark green
Fall Foliage – yellow
Hardiness Zone – 3
Cultural Requirements – prefers full sun and moist soil, pH adaptable, pollution tolerant
Comments – Uniform pyramidal habit, this compact selection is well suited for use as a street tree. The lateral branches are arranged uniformly around a strong central leader, and the plant may reach 45′ tall with a spread of 15′. Obtained in 1994 from J. Frank Schmidt and Son Co.

Malus x ‘Silver Drift’
(Silver Drift Crabapple)

Growth Habit – Rounded
Height: 10-15 ft.
Spread: 10-15 ft.
Foliage – Medium green
Flower – Red buds open to white flowers
Fruit – Small cherry red fruit in September maturing to dark red by November, showy
Hardiness Zone – 4
Cultural Requirements: Full sun and moist soil
Comments – A fast growing tree with showy fruit that is very persistent for a long season of interest. Excellent resistance to apple scab, rust and fire blight. Obtained in 2002 from Bailey Nurseries.

Acer saccharum ‘Sugar Cone’
Sugar Cone Sugar Maple

Growth Habit – Conical shape
Height: 25’
Spread: 10-12’
Foliage – Medium green
Fall Foliage – Yellow, orange
Hardiness Zone – 3
Cultural Requirements – Adaptable to alkaline conditions. Prefers moderately moist, fertile soils. Tolerates some shade.
Comments Obtained in 2004 from Schichtel’s Nursery which is one of their own introductions. It is a dwarf and compact tree which is very dense in leaf and outstanding twiggy winter form. This clone is slow growing.

Aesculus x ‘Homestead’
Homestead Buckeye

Growth Habit – Rounded to broad
Height: 35′
Spread: 25′
Foliage – Medium green
Fall Foliage – Yellow, orange, red
Flower – Yellowish-red, sterile
Hardiness Zone – 4
Cultural Requirements – Prefers a more moist, well drained soil and performs poorly in a dry site. Grows in sun or partial shade.
Comments – Obtained in 2006 from Carlton Nursery. This is a hybrid of A. flava x A. glabra bred at South Dakota State University.

Prunus sargentii ‘JFS-KW58’
Pink Flair® Cherry

Growth Habit – Upright, narrow vase shape
Height: 25′
Spread: 15′
Foliage – Dark green
Fall Foliage – Red, orange
Flowers – Single pink flowers in clusters
Hardiness Zone – 4
Cultural Requirements – Prefers full sun and moderately moist soils.
Comments – Obtained in 2001 from J. Frank Schmidt and Son Nursery. Blooms appear several weeks later than most cherries often avoiding frost damage. Bark has a rich, chestnut color with a polished appearance. The upright narrow vase shape gives good winter appeal and the compact habit makes it a good choice for urban landscapes.

Pyrus calleryana ‘Jackzam’
Jack® Dwarf Flowering Pear

Growth Habit – Upright, oval
Height: 16′
Spread: 10′
Flowers – White
Foliage – Dark green, glossy
Fall Foliage – Orange/red
Hardiness Zone – 4
Cultural Requirements – Very adaptable to many soils, tolerates some dryness and pollution, prefers full sun
Comments – Obtained in 2005 from Femrite Nursery Company. The compact growth habit gives this plant the unusual combination of a formal appearance in a low maintenance tree. Mature size is said to be half the size of the species.

Sambucus nigra ‘Eva’ PP 15,575
Black Lace Elder

Growth Habit – Upright
Height: 6-8′
Spread: 8-10′
Flowers – This plant blooms in early summer on old wood with creamy, pink flowers.
Foliage – Black-purple, finely cut
Hardiness Zone – 4
Cultural Requirements – Prefers moist soils but will tolerated dry conditions. Adaptable to acid or alkaline soil. Grows well in sun to part-sun.
Comments – Obtained in 2005 from Proven Winners. The dark foliage makes it effective in groupings or masses. It is a good shrub for use in the landscape or as a potted shrub on the patio. Would be a good cold hardy alternative to Japanese maple. Blackish red berries appear in fall which can be harvested for making elderberry wine and jam, or left on the plant to attract birds and other wildlife.

Syringa pekinensis
Peking Lilac

Growth Habit – Rounded
Height: 20′
Spread: 20′
Flowers – Cream colored flowers bloom in three to six inch panicles in early summer.
Foliage – Medium green
Fall Foliage – Light yellow
Hardiness Zone – 3
Cultural Requirements – Prefers full sun to partial shade. Tolerates some drought and is pH adaptable.
Comments – Obtained in 1981 from Valley Nursery. It is mainly grown multi-stemmed and develops an upright arching, loose and open growth habit. The exfoliated red to brown bark adds interest to the winter landscape.

Cercidphyllum japonicum

Katsuratree

Growth Habit –  narrowly pyramidal as young tree and variable as it matures.

Height:  15-20’ at CSU, 40-60’ in literature

Spread:  10-15’ at CSU, 20-30’ in literature

Flowers –  not showy

Foliage –  emerge reddish purple and change to blue green

Hardiness Zone –  4

Fall Foliage – bright yellow

Cultural Requirements –  prefers moist soil and full sun.  Adaptable to various soil pH.

Comments –   Has a very pleasing scent as leaves drop in Fall – somewhat like toasted marshmallows or brown sugar.  Obtained in 1981.

Chamaecyparis pisifera ‘Filifera Aurea’

Stringleaf Japanese Falsecypress

Growth Habit –  mounding or broad cone shape with weeping branches

Height:  4-6’ at CSU, 15-20’ literature

Spread:  5-8’

Foliage –  drooping, long, thread-like foliage, yellow/green

Hardiness Zone –  5

Cultural Requirements –  prefers moist, well-drained soil and full sun or partial shade, does not like windy sites

Comments –  the weeping, thread-like foliage provides excellent texture and color.  Foliage is  attractive in winter.  Obtained in 1983.  Grows slowly.

Hydrangea paniculata ‘Tardiva‘

Late Panicle Hydrangea

Growth Habit –  upright, coarse

Height:  4-6’ at CSU, 6-8’ catalog

Spread:  4-5’ at CSU, 8-10’ catalog

Flowers – White, buds have pink edges. 6” panicles, blooms on new wood in late-August thru September

Foliage –   medium to dark green

Hardiness Zone –  3

Fall Foliage –  yellow, fair to good

Cultural Requirements –  adaptable but prefers loamy, moist soil.  Urban tolerant.  Takes sun or part-shade.

Comments –  Later blooming than most hydrangeas – good for late season color.  Reportedly resistant to Japanese beetle.  Obtained in 1998.

Magnolia x soulangiana ‘Alexandria’
Alexandria Saucer Magnolia

Growth Habit –  upright oval

Height:  10-12’ at CSU, 20-30’ in literature

Spread:  10-12’ at CSU, 20-30’ in literature

Flowers –  large, attractive bicolor of rose-purple outside and white inner petals, blooms in mid-April

Foliage –  medium green

Hardiness Zone –  4

Fall Foliage –  yellow

Cultural Requirements –  prefers moist, deep soil and full sun

Comments –   Early to flower and makes a dramatic statement at the end of winter.  Flower buds susceptible to early frost and prefer protected area.  Obtained in 1980.

Malus ‘Guinzam’
Guinevere Crabapple

Habit – Dwarf tree with rounded habit.
Height: 8-10′, spread: 10′
Flowers – pink buds open to white flowers in late May
Fruit – Bright red fruit, 3/8″, persistent
Fall Foliage – yellow
Cultural Requirements – well drained and moderately moist soil, sun.
Comments – No significant disease problems. Received in 1992 from Bailey Nurseries and has done well in our research plots.

Juniperus sabina ‘Mini Arcadia’
Mini Arcadia Savin Juniper

Growth Habit – a lower and more spreading growth habit than ‘Arcadia’. Very uniform appearance.
Height: 1-2′, spread: 5-8′
Fall Foliage – keeps soft green color all winter
Cultural Requirements – Can tolerate dry soils and is adaptable. Sun.
Comments – Not as susceptible to Juniper blight as compared to J. horizontalis. Received from the Greenleaf Nursery in 1988.

Cercocarpus ledifolius
Curleaf Mountain Mahogany

Growth Habit – open spreading habit, irregular
Height: 10-20′, spread: 8-12′
Leaves – tough, leathery, dark green leaves with edges that curl under. Evergreen.
Fruits – seeds have “fuzzy tails” which provide fall interest
Cultural Requirements – sun, drought tolerant.
Comments – When pruned into a small tree it shows off a very attractive silver/gray bark. Received from Fort Collins Nursery in 1982.

Funded by: Agricultural Experiment Station Project 713, J. Frank Schmidt & Son Foundation, Colorado Nurseryman Research & Education Foundation, Colorado Tree Coalition and various nurseries throughout the state and country. In-kind donations were received from Organix, and the City of Fort Collins.

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