Garden-in-a-Box Boulder & Trees Across Boulder

Trees Across Boulder

Trees Across Boulder was launched in 2007 by the Center for ReSource Conservation in conjunction with the City of Boulder's Water Conservation Office, Urban Forestry Department and Parks and Recreation Department to encourage City of Boulder residents to plant a diverse variety of trees that do well in our arid Colorado climate.

The Urban Forestry Department has determined which species is available in this spring. You must be a City of Boulder resident to participate in the program. Each tree is $50.00 and comes with instructions on how to plant and maintain the tree.

If you received a letter from the City of Boulder indicating that you need to remove any Black Walnuts from your property or if you would like to get information about purchasing a tree through this program, please click here or call 303.999.3820 ext. 217. Thank you!

We are sold out of all trees for 2008.  Please call us at 303.999.3820 ext. 217 or
email us with any inquiries about the program. Thank you for a great sale!

Species chosen by the Urban Forestry Department

Tree Sizes are 1.25 caliper inch and Sapling heights range from 5-8 feet.  All trees come balled and burlapped.

Ohio Buckeye Mature height: 20’-40’ Mature spread: 20’-40’ Ohio Buckeye has unusual, large leaves that make this tree interesting and attractive. Hardy and drought tolerant. Large light brown fruit capsules follow flowers in summer and fall.
Western Catalpa (SOLD OUT) Mature height: 40’-60’ Mature spread: 30’-50’ Catalpa is adaptable to dry alkaline soils and can withstand extreme heat. It has large, showy white flowers in early summer. Catalpas have an informal, rugged silhouette that adds much winter interest.
Ruby Red Horsechestnut Mature height: 30’-40’ Mature spread: 25’-30’ Red Horsechestnut are a smaller variety of Horsechestnut. Stunning large crimson flowers appear in the late spring. Fall color is yellow.
Common Hackberry (SOLD OUT) Mature height: 50’-60’ Mature spread: 40’-50’ Hackberry is a native tree that adapts to a wide range of soil conditions and is quite drought tolerant. It performs well under windy conditions. The trunk and older branches have narrow, corky ridges that add winter interest to the landscape. It produces small, reddish-purple fruit in the fall that attracts birds.
Thornless Cockspur Hawthorn (SOLD OUT) Mature height: 15’-25’ Mature spread: 15’-25’ Hawthorns have adaptable water requirements and tolerate alkaline soil conditions. They have beautiful white flowers in the spring and often turn bronze to red in the fall.
'Cleveland Select' Pear (SOLD OUT) Mature height: 30’-35’ Mature spread: 15’-20’ ‘Cleveland Select’ pear, known also as Chanticleer pear, is adaptable to all soil types and drought tolerant. Chanticleer pears consistently produce nice, white flowers in early spring and red-purple fall color. Does not produce fruit.
Bur Oak Mature height: 50’-80’ Mature spread: 50’-80’ Bur oak is a massive tree with a broad rounded crown at maturity. It is drought tolerant and can tolerate a wide range of soil conditions. Leaves turn yellow brown to brown in the fall.
Red Oak Mature height: 60' Mature spread: 70' Red Oak is a large tree with frantastic autumn shades of brilliant red and yellow.
Garden Essentials SOLD OUT! Drip kits and control clocks eligible for 50% rebate from the City of Boulder.  Visit www.BoulderSavesWater.net to get a rebate form.
Drip Kit SOLD OUT Cost: $46 each ($23 with rebate) The Yard n' Garden Kit from Drip Works comes with all the essentials to start a drip system. Step by step installation instructions included.
Control Clock SOLD OUT Cost: $32 each ($16 with rebate) This battery operated control clock allows you to program the runtimes and days you want to water. Easy programming with digital display screen.
Compost Tea SOLD OUT Cost: $3 per gallon Eco-cycle's "Microbe Brew" compost helps balance the soil nutrients for healthy plant growth. This compost is free of chemicals and does not require any prep work.

Detailed Tree Descritions

Ohio Buckeye (Aesculus glabra)

Mature Spread: Crown Width - 20 to 40 feet.
Mature Height: Crown Height - 20 to 40 feet.

Description: A medium-sized tree with a dense oval to rounded crown, branching quite low, becoming rounded with age. Bark is smooth and light gray becoming thick, ashy gray and deeply furrowed when mature. Leaves emerge bright green deepening to medium green in spring. The leaves are opposite, palmately compound

with 5 leaflets which are smaller, elliptical (widest near the center of the leaflet), with a drawn-out and pointed tip (leaf length - 6 to 9 inches; leaf width - 5 to 6 inches.)  The flowers are greenish yellow, about 1-2 cm long, in large, showy, upright, branched, terminal clusters at ends of leafy branches. Blooms emerge in early spring just before or with the foliage. The fruits produced are a rounded capsule about 3 cm wide, with a , thick, leathery green husk, inside are seeds, usually 1, which are smooth, glossy, chestnut-brown seeds, each with a pale scar (the “buck's eye”). Fall colors for the Ohio Buckeye are a developing yellow to amber/orange and may be nearly defoliated by late summer.

Needs: Young trees show moderate growth rates and may begin producing fruit at 8 years. Most trees live 60- 80 years. The Ohio Buckeye prefers shady conditions in its youth, but grows in full sun to full shade from youth through maturity. The soil preferences are moist, well-drained soils of variable pH that are rich and deep.  Needs adequate moisture during drought, or leaf scorch may become a problem. 

Benefits: The tree is an attractive ornamental, best in open, natural settings or parks because of its broad crown. Attractive flowers with red to orange fall colors.

Concerns: Leaf scorch and leaf blotch are usually the most serious problems of Ohio buckeye and may slow the growth rate however causes no permanent damage. All parts of the plant (leaves, bark, fruit) are toxic if very large quantities are ingested. Tree emits a strong odor when leaves, bark, broken twigs, and flowers are crushed.

Ruby Red Horsechesnut (Aesculus x carnea 'Briotii')

Mature Spread: 25 to 30 feet
Mature Height:  30 to 40 feet

Description: Pyramidal in shape when very young, Red Horsechestnut develops slowly into a round, very dense shade tree by five to seven years of age. The bark of Horsechestnut becomes broken into fissures and thick plates with maturity. In addition, this tree frequently has a divided trunk at a low height, giving it several huge branches that contribute to its dense canopy. Red Horsechestnuts foliage is dark green and course textured composed of five to seven leaflets, 4 to 8 inches length which radiate like a fan from a central point. Flowers are a deep scarlet about 10-inches-long and stand stiffly upright or slightly angled. The flowers bloom in late spring after the leaves have fully expanded and are quite attractive to bees and hummingbirds.  The fruits of Horsechestnut are composed of one or two seeds enclosed in a spiny brown husk and may occur singly or in clusters. The Red Horsechestnut produces yellow fall color.

Needs: Slow to medium growth rate. Provide full sun or light shade. Soil preferences are moist, well-drained soils including sand, loam, or clay. Pruning is needed for strong structure, but exposing the trunk suddenly to direct sun may crack the bark so keep it shaded as much as possible by leaving lower branches on the tree.

Benefits: Makes a great street tree when provided with some irrigation during drought. It holds up well in urban areas, even in restricted and compacted soil spaces.

Concerns: Resiliant to pests/ diseases, although Horsechestnut often suffers from leaf scorch.

Western Catalpa (Catalpa speciosa)

Mature Spread: 30' to 50'
Mature Height:  40' to 60'

Description: This tree has an asymmetrical, irregular appearance giving it a lot of character. Bark is grayish-brown, ridged and furrowed.  Leaves are opposite or whorled, a dark kelly green and heart shaped; 6" to 12" long; 5" to 8" wide. The large, white flowers are bell-shaped, 2" in diameter, 4" to 8" long and bloom in late May and June.

Green Seed pods resemble beans, 8" to 20" long, and last into winter.

Fall color is briefly yellow-green, then dull brown.

Needs: Growth rate is medium to fast once established (Terminal shoot can be 3' per year.) Provide full sun to partial shade. The Western Catalpa is tolerant of a wide range of soil conditions.

Benefits: Plant them as accent trees in yards and parks. In areas with wide parkways, they can be planted as street trees.

Concerns: No real concerns.

Hackberry (Celtis occidentalis)

Mature Spread: 40 to 50 feet.
Mature Height: 50 to 60 feet.

Description: Narrow when young, vase-shaped crown structure when mature. The bark is grayish brown, with characteristic corky ridges becoming somewhat scaly. The leaves are 2 ½ to 4 inches long, and 1 ½ inches wide, oval to lance-shaped and  bright-green above, paler below. Pale-green flowers. The fruit is 1/4 inch to 1/3 inch in diameter, oval to somewhat round, dark red or purple, ripening in September and October, but remaining on the tree for several months. Fall color is yellow.

Needs: Growth rate is medium to fast, but not uniform in early years. Requires full sun to partial shade, planting close to the west side of the house (no closer than 12 feet) will provide a comforting afternoon shade. Performs well on a variety of soils and moderately drought tolerant. Hackberry may compensate in times of drought by dropping a portion of the leaves when under stress. Branching habit looks very scattered and in need of pruning during the first 10 years. It needs pruning to make it look decent and to select a main trunk in these years. Once established though it has a nice vase shaped to oval crown.

Benefits: Excellent tree for wildlife, birds use the mature trees for nesting sites and feed on the fruit. Fruit is also eaten by many birds and mammals. Best suited for open areas and along streets. It would fit well into the home landscape if there is a need for a large tree and lots of shade.

Concerns: The most common appearance problem is the hackberry nibble-gall which forms on the underside of the leaves. If severe, the leaves do get disfigured. In most cases, no treatment is necessary.

Thornless Cockspur Hawthorn (Crataegus crus-galli ‘Inermis’)

Mature Spread: 15 to 25 feet
Mature Height: 15 to 25 feet

Description: Rounded, spreading short tree with dense horizontal branching that is available as single stem tree.  Bark is brown, exfoliating in thin gray strips, with winter interest.  It has a dark green glossy leathery leaf and clusters of simple small creamy white flowers that form in late spring, 2"-3" clusters. Small bright red berry that persists in late summer/ early fall and is produced in masses, 3/8" - 1/2". Fall colors range from a bright gold to rusty orange.

Needs: Once the tree is established is will grow 12 to 18 inches a season. The Thornless Cockspur Hawthorn requires full sun.  It grows best in drained soils but will tolerate clay soils. The Cockspur Hawthorn is a drought resistant landscape plant with low water needs but does best when well watered

Benefits: They grow well in park and home settings as well in planters, and makes an excellent accent to the landscape. Lacks dangerous thorns.

Concerns: Reisistant to Cedar Rust with no serious pest problems.

'Cleveland Select' Pear (Pyrus calleryana 'Chanticleer')

Mature Spread: 30' to 35'
Mature Height: 15' to 20'

Description: Medium Sized ornamental upright-pyramidal tree. Leaves are a glossy dark green, oval in shape, 5-7 cm long.  Spring produces clusters of beautiful white blossoms that last two weeks before leaves appear, flowers are five petals and are about 2-3 cm in diameter.  Fall brings brilliant colors, anything from yellow and orange to a more common red or purple.

Needs: Growth rate is 2’ per year. Requires full Sun and adaptable to many soils. Pruning is recommended in early winter or spring.

Benefits: Cleveland Select Pear is able to withstand storm damage during the high winds of severe thunderstorms or when ice storms occur. Has wonderful landscape value and good for areas that have little lateral space to spread.  Less suxsceptible to early freezes than other Pears and tolerates dryness and pollution.

Concerns: No real concerns.

Bur Oak (Quercus macrocarpa)

Mature Spread: 50 to 80 feet.
Mature Height: 50 to 80 feet.

Description: Very stout branches, large long-lived tree on good sites, The upright growth habit of youth and middle age gives way to a broad-spreading canopy with age. Mature dark gray bark becomes highly ridged and deeply furrowed. Leaves are dark green and lustrous above, grayish to whitish-green below. Flowers are Catkins and the male is yellow-green, while the female is reddish. Its large acorns only take a single season to develop, and are nearly completely covered by a rough, frilled cap, ½” to ¾”, ripening in early to mid-autumn. To some the acorns look as if they are covered in moss. Fall color is usually yellow brown and ineffective.

Needs: Once established, trees can grow up to two feet per year on favorable sites. Full sun preferred, but is moderately shade tolerant. Does well in a wide variety of soils. Drought tolerant, it is found in both continuously moist as well as very dry sites.

Benefits: Bur Oak is also called Mossycup Oak. Excellent for landscaping, yards, and parks.

Concerns: Leaf and twig galls are commonly found, but rarely damage the tree. Sensitive to construction injury as they are somewhat sensitive to root compaction.

Red Oak (Quercus rubra)

Mature Spread: 70'
Mature Height: 60'

Description: Straight and tall, stout branches growing at right angles to the stem, forming a narrow round-topped head. Dark redish gray brown bark features ridges that appear to have shiny stripes down the center all the way down the trunk.  Leaves are dark green and smooth, sometimes shining above, yellow green, smooth or hairy on the axils of the veins below. The leaves are alternate, seven to nine-lobed, oblong-ovate to oblong, five to ten inches long, four to six inches broad. Trees have pendulous pollen-bearing catkins in mid-spring that are the "showy" golden-brown flowers seen from a distance. The winter buds are a dark chestnut brown, ovate, acute, one-fourth of an inch long, The acorns ripen in the spring of alternate years. In autumn they are quite impressive, ranging from brick red to scarlet, although some trees may have golden- yellow to yellow-brown foliage.

Needs: Growth is rapid and vigorous. Full to partial sun (is shade tolerant in youth). The tree prefers moist, deep, rich, well-drained soils of slightly acidic pH.

Benefits: This tree is also known as the Northern Red Oak.

Concerns: Some specimens develop chlorosis in high pH (alkaline) soils.

Pictures courtesy of High Country Gardens, Little Valley Wholesale Nursery, Utah Government, City of Loveland, georgiaperennial.org, hotgardens.net and ogis.co.jp