Fact Sheet ST-454 October 1994 Picea pungens ‘Iseli Foxtail’ ‘Iseli Foxtail’ Colorado Spruce1 Edward F. Gilman and Dennis G. Watson2 INTRODUCTION Colorado Spruce has a horizontal branching habit and grows taller than 75 feet in its native habitat, but is normally seen at 30 to 50 feet in landscapes (Fig. 1). This cultivar is probably about the same size as the species. The tree grows about 12 inches per year once established but may grow slower for several years following transplanting. Needles emerge as a soft clump, changing to a stiff, pointed needle sharp to the touch. ‘Iseli Foxtail’ has striking, light-blue needles which are more attractive than the species. The crown is shaped like a pyramid, ranging from 10 to 20 feet in diameter. GENERAL INFORMATION Scientific name: Picea pungens ‘Iseli Foxtail’ Pronunciation: PIE-see-uh PUN-jenz Common name(s): ‘Iseli Foxtail’ Colorado Spruce, ‘Iseli Foxtail’ Colorado Blue Spruce, ‘Iseli Foxtail’ Blue Spruce Family: Pinaceae USDA hardiness zones: 4 through 8A (Fig. 2) Origin: native to North America Uses: recommended for buffer strips around parking lots or for median strip plantings in the highway; screen; specimen; Christmas tree; no proven urban tolerance Availability: somewhat available, may have to go out of the region to find the tree Figure 1. Middle-aged ‘Iseli Foxtail’ Colorado Spruce. DESCRIPTION Height: 30 to 50 feet Spread: 10 to 20 feet Crown uniformity: symmetrical canopy with a regular (or smooth) outline, and individuals have more or less identical crown forms Crown shape: columnar; pyramidal Crown density: dense 1. This document is adapted from Fact Sheet ST-454, a series of the Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: October 1994. 2. Edward F. Gilman, associate professor, Environmental Horticulture Department; Dennis G. Watson, associate professor, Agricultural Engineering Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611. Picea pungens ‘Iseli Foxtail’ -- ‘Iseli Foxtail’ Colorado Spruce Page 2 Figure 2. Shaded area represents potential planting range. Growth rate: medium Texture: fine Foliage Leaf Leaf Leaf Leaf Leaf Leaf arrangement: spiral (Fig. 3) type: simple margin: entire; terminal spine shape: needle-like (filiform) venation: parallel type and persistence: evergreen; needle leaf evergreen Leaf blade length: less than 2 inches Leaf color: blue or blue-green Fall color: no fall color change Fall characteristic: not showy Flower Flower color: green; orange; purple Flower characteristics: inconspicuous and not showy; spring flowering Fruit Fruit Fruit Fruit Fruit Fruit shape: elongated; oval length: 3 to 6 inches; 1 to 3 inches covering: dry or hard color: brown characteristics: does not attract wildlife; inconspicuous and not showy; no significant litter problem Trunk and Branches Trunk/bark/branches: droop as the tree grows, and will require pruning for vehicular or pedestrian clearance beneath the canopy; not particularly showy; should be grown with a single leader; no thorns Pruning requirement: needs little pruning to develop a strong structure Breakage: resistant Current year twig color: brown Current year twig thickness: thick Picea pungens ‘Iseli Foxtail’ -- ‘Iseli Foxtail’ Colorado Spruce Page 3 same blue foliage effect without the disease problem. Deodar Cedar also carries this light blue color throughout the year. Also, the wax coating on the needles of Blue Spruce which give the blue color can be washed off by some pesticides. Check the label and test the spray on a small scale before spraying. Figure 3. Foliage of ‘Iseli Foxtail’ Colorado Spruce. Culture Light requirement: tree grows in part shade/part sun; tree grows in full sun Soil tolerances: clay; loam; sand; acidic; occasionally wet; alkaline; well-drained Drought tolerance: high Aerosol salt tolerance: moderate Soil salt tolerance: moderate Other Roots: surface roots are usually not a problem Winter interest: no special winter interest Outstanding tree: tree has outstanding ornamental features and could be planted more Invasive potential: little, if any, potential at this time Verticillium wilt susceptibility: not known to be susceptible Pest resistance: very sensitive to one or more pests or diseases which can affect tree health or aesthetics A number of other cultivars are listed. The most common cultivar is ‘Glauca’, the Blue Colorado Spruce. The blue trees are sometimes grown from seeds, so they vary in degree of blue coloration. For reliable blue color, purchase a grafted, named cultivar selected for its blue color. The list of cultivars is not long: ‘Argentea’ (Silver Colorado Spruce) - silvery foliage color; ‘Glauca’ (Blue Colorado Spruce) - bluish foliage, the nicest cultivar; ‘Glauca Procumbens’ - bluish foliage, height about two feet but spread several times the height; ‘Globosa’ - three feet tall, blue foliage; ‘Hoopsii’ bluish foliage; ‘Moerhiemii’ (Moerhiem Spruce) compact, dense and very blue; ‘Pendens’ (Koster’s Blue Spruce) - weeping habit, must be staked to get it to take tree form, blue foliage; ‘Thompsoni’ - bluish foliage. Pests Two gall-forming insects commonly attack Spruce. Eastern Spruce gall adelgid forms pineapple like galls at the base of twigs. Galls caused by Cooley’s Spruce gall adelgid look like miniature cones at the branch tips. The gall adelgids do not kill trees unless the infestation is heavy. A few galls on a large tree are not serious. USE AND MANAGEMENT Colorado Spruce casts dense shade when branched to the ground, so no grass grows beneath it. It lends a ridged, formal effect to any landscape due to the stiff, horizontal branches, but the blue foliage softens this effect. It is often used as a specimen or as a screen planted 10 feet apart. This may be the best Blue Spruce adapted to the heat in the south, and has grown nicely in Raleigh, N.C. for a number of years. The tree prefers a rich, moist soil, and benefits from irrigation in dry weather. Trees benefit from a layer of mulch extending beyond the edge of the branches. This keeps roots cool and reduces moisture loss from the soil. Grows in full sun or the shade on the north side of a building. It tolerates clay and poor drainage for a short period. Susceptibility to canker makes the species a questionable choice for large-scale planting in the eastern states. The susceptibility of this cultivar is not clear at this time. Substitute White Fir (Abies concolor) for the In northern areas, Spruce budworm larvae feed on developing buds and young needles. The yellowish brown caterpillars are difficult to see. The Spruce needle miner makes a small hole in the base of a needle then mines out the center. Dead needles are webbed together and can be found on infested twigs. Pine needle scale is a white, elongated scale found feeding on the needles only. Populations would have to be quite high to cause major damage. Mites can be a serious problem in summer after hot dry weather. The small insects can’t be readily seen with the naked eye. The first noticeable symptoms are yellowing of the oldest needles on infested branches. Close inspection with a magnifying glass will confirm the presence of the mites. Picea pungens ‘Iseli Foxtail’ -- ‘Iseli Foxtail’ Colorado Spruce Diseases Cytospora canker infects a branch then eventually kills it. The lower branches are attacked first then progressively higher branches. The needles turn brown to reddish brown and eventually drop off. White resin patches are seen on infected branches. Prune off infected branches. Water Spruces during dry weather but keep the foliage as dry as possible. Spruce may be attacked by needle casts. One causes needles to turn yellow or brown and drop off. Another needle cast affects the lowest needles first then moves up the tree. Infected needles are a mottled yellow. Several rust diseases attack Spruce but these are rarely seen. Infected needles turn yellow and drop off. Page 4