Culture Notes
This graceful, small deciduous conifer reaches 15 to 25 feet in height forming an elegant mass of drooping foliage and branches. Form varies from one tree to the next depending on how the tree was trained in the nursery. Foliage turns a brilliant yellow in the fall for a short time but long enough to make a striking landscape statement. The reddish-brown bark is rugged and furrowed, showing nicely in the winter.
Larch should be grown in full sun on deep, rich, well-drained, moist acid soil where the trees can be protected from harsh, cold winds. The trees should not be planted in limestone soils and they are not tolerant of clay unless located on a slope where drainage would be excellent. Planted on an appropriate site, Larch will last for many years. It is best to locate the tree where the roots can expand into the surrounding soil unobstructed by pavement, buildings or other urban structures.
Maintain adequate mulch area
Be sure to clear all turf away from beneath the branches and mulch to the drip line (the edge of the branches), especially on young trees, to reduce competition with turf and weeds. This will allow roots to become well established and keep plants healthier. Locate the tree properly, taking into account the ultimate size, since the tree looks best if it is not pruned to control size. The tree can enhance any landscape with its delightful spring flush of foliage. It can be the centerpiece of your landscape if properly located.
Tree establishment specifications
Choose good quality trees for planting. The most common cause of young tree failure is planting too deep. In most instances, the point where the top-most root in the root ball originates from the trunk (referred to as the root flare zone or root collar) should be located just above the soil surface. You may have to dig into the root ball to find the root flare. If there is nursery soil over this area, scrape it off. Never place ANY soil over the root ball. The planting hole should be at least twice the width of the root ball, preferably wider because roots grow best in loose soil. In all but exceptional circumstances where the soil is very poor, extensive research clearly shows that there is no need to incorporate any amendments into the backfill soil. Simply use the loosened soil that came out of the planting hole. Simply planting with the topmost portion of the root ball slightly higher than the surrounding soil might still install the tree too deep - be sure to locate the root flare.
Weed suppression during establishment is essential. Apply a 3-inch thick layer of mulch to at least a six-foot diameter circle around the tree. This area should be at least two feet in diameter for each inch of tree trunk diameter and maintained during the establishment period. Apply a thinner layer of mulch directly over the root ball but keep it at least 10 inches from the trunk. This allows rainwater, irrigation and air to easily enter the root ball and keeps the trunk dry. Placing mulch against the trunk and applying too thick a layer above the root ball can kill the plant by oxygen starvation, death of bark, stem and root diseases, prevention of hardening off for winter, vole and other rodent damage to the trunk, keeping soil too wet, or repelling water.
Regular irrigation after planting encourages rapid root growth that is essential for tree establishment. Trees provided with regular irrigation through the first growing season after transplanting require about 3 months (hardiness zones 9-11), 6 months (hardiness zones 7-8), or one year or more (hardiness zones 2-6) per inch of trunk diameter to fully establish roots in the landscape soil. Trees in desert climates may take longer to establish. Trees that are under-irrigated during this establishment period (and most trees are) often require additional time to establish because roots grow more slowly.  Be prepared to irrigate through the entire establishment period, especially during periods of drought.
Irrigation also helps maintain and encourage the desirable dominant leader in the tree canopy on large-maturing trees. Instead of a dominant leader, trees that are under-irrigated during the establishment period often develop undesirable, low, co-dominant stems and double leaders that can split from the tree later.
Unlike established plants, which do best with deep, infrequent irrigation, research clearly shows that recently transplanted trees and shrubs establish quickest with light, frequent irrigation. For trees planted in spring or summer, provide one (cooler hardiness zones) to three irrigations (warmer hardiness zones) each week during the first few months after planting. Daily irrigation in the warmest hardiness zones provides the quickest establishment. Following the initial few months of frequent irrigation, provide weekly irrigation until plants are fully established. With every irrigation, apply one (cool climates) to two (warm climates) gallons of water per inch trunk diameter (e.g. 2 to 4 gallons for a 2-inch tree) over the root ball only. In most landscapes that receive more than 30 inches of rain or irrigation annually, if the mulch area is maintained weed-free, irrigation does not need to be applied outside of the root ball. Never add water if the root ball is saturated.
In cooler hardiness zones, in all but the driest years, irrigation of spring- and summer-planted trees usually can be discontinued once fall color has begun. Irrigation of fall planted trees, however, should be continued until foliage has dropped from the deciduous trees in the region. In warmer climates, irrigate fall-and winter-planted trees as described for the spring- and summer-planted trees.
In drier, desert climates there is benefit to be gained from applying additional irrigation outside of the root ball area. This is best done by making a large diameter berm four to six inches high, then filling it with water so it percolates into the soil. For the first two years, irrigate twice each week through the spring, once per week in summer provided monsoons arrive, and twice each week again in fall if it remains warm. Taper off watering to once or twice each month in winter and resume twice weekly next spring. For years three to five, water twice per month in spring, summer, and fall and once or twice per month in winter. During years five through seven, water once every three weeks in warm weather and once every six weeks in winter. After this, the drought-tolerant desert trees should be able to survive on natural rainfall.
Trees with good, strong structure need no pruning at planting, except to remove broken twigs. Do not remove branches to compensate for root loss - research has shown that this can be detrimental to establishment.
Spring transplanting best
Balled-and-burlapped and bare root trees recover best when transplanted in late winter or early spring in the cooler portions of North America. This usually corresponds to the initiation of root growth.
Pests, Diseases and Damaging Agents
This genus is sensitive to fluoride air pollution, sources of which include glass and brick manufacturing plants and other facilities that heat or treat with acid materials containing fluoride. Symptoms due to fluoride injury are more prominent on the side of the plant facing the pollution source. In deciduous plants, symptoms include leaf browning along the margins of the leaves. A dark brownish band may appear along the boundary between healthy green tissue and the affected brown tissue. Eventually, the entire leaf may turn brown. In conifers, the tips of the current year's needles turn reddish brown. Older needles are typically unaffected. If you suspect fluoride has injured this plant, look in the neighborhood for gladiolus plants. They serve as indicator plants for fluoride air pollution damage because they are very sensitive to it. Other sensitive plants include ash, maple, oak, white pine, poplar, and redbud. Plants that resist injury include birch, flowering cherry, dogwood, hawthorn, American linden, juniper, pear, spirea and sweet gum.
This genus is sensitive to sulfur dioxide air pollution. Sources of sulfur dioxide air pollution include fossil fuel combustion, smelting and refining of ores. Damage usually is confined to urban areas near power stations. Acute injury typically occurs when plants are exposed to high concentrations for a short period. In deciduous plants, tissue between veins on the upper and lower side of the leaf turns yellow, white or tan-brown. The veins usually remain green. In conifers, the tips of needles turn reddish-brown. As damage accrues, the discoloration progresses toward the base of the needle. Deciduous plants exposed to low concentrations of sulfur dioxide for long periods of time (chronic exposure) show a general chlorosis or yellowing of the foliage. Needles on conifers exposed to chronic sulfur dioxide turn yellow and drop from the tree prematurely. If you suspect sulfur dioxide has injured this plant, look in the neighborhood for blackberry, raspberry, pumpkin, or squash plants. These serve as indicator plants for sulfur dioxide air pollution damage because they are very sensitive to it. Other sensitive plants include apple, birch, white pine, poplar, blue spruce and zinnia. Plants that resist injury include box-elder, dogwood, black gum, juniper, maple, spruce and sycamore.
This plant is sensitive to damage from ozone air pollution. Damage can occur in urban or rural areas because ozone can travel long distances away from where it is formed. Typical symptoms on deciduous trees are a flecking or stippling only on the upper side of the foliage between large veins. The small spots or flecks are white, tan or orange-red. Spots or flecks from one-eighth to one-quarter inch long appear on needles of sensitive conifers. Yellow bands that girdle the needle may form, eventually causing the tips of the needles to die and/or needles to drop from the plant. If you suspect ozone is causing damage on this plant, locate White Pines (Pinus strobus) in the area to see if they are damaged. White Pines are very sensitive to ozone damage and can serve as indicators of the presence of ozone in concentrations high enough to cause plant damage.Â