Printer Version for Larch Care
Larch (Larix sp.)
Planting Larches
American larches are able to withstand severe cold. They survive winter temperatures as low as -50° F. On the other hand, they hate heat so they are not happy below zone 4. Japanese and European Larches can live down a few zones to 6 or 7. Because they have shallow, fibrous root systems, larches transplant easily. Choose a sunny location, but not a droughty one. These trees do not mind moist soil, even enjoying wet feet, and are perfect for those areas on the property where corrective measures for soggy soil have not been effective. The European and Japanese Larches will tolerate a bit drier soil than will the American Larch. They are not particular about soil type, managing in clay and limestone as well as loam. Soil should be mildly acid to neutral (pH 6.5 to 7.5). Choose young trees from the nursery either in containers or with burlap wrapped roots and soil.
Caring For Larches
Spring
A 2 or 3-inch layer of some attractive organic mulch offers many benefits to trees. Spread wood chips, chopped leaves, shredded bark or a similar material in a circle directly on the soil under the tree.
Summer
Larches do not require routine pruning. If it is necessary to remove injured or diseased branches, it is best to prune in mid-summer.
Larches are most comfortable in moist soil. Of course, as with all new transplants it is important to water them when they are newly planted. Also, during times when rainfall is irregular and drought conditions prevail, even mature, well-established larches appreciate supplemental watering. Check the soil under the tree. If it is dry down several inches, run a drip system or sprinkler for minutes or so every week to 10 days until rain falls.
Fall
Do not fertilize larches until they have been in place at least a year. Then an annual light feeding of a granular all-purpose fertilizer is recommended. Sprinkle it on the soil under the tree, out as far as the branches extend for the rain to soak in. Use 1/2 pound of fertilizer for each 1/2 inch of trunk diameter, measured at the base.
Winter
While larches are able to handle very cold winters, they are vulnerable to wind damage in the first three or four years in the ground Protect young larches that are exposed to wind with a screen of burlap or the white spun agricultural fabric that admits air and light, but will block harsh winds. Do NOT use plastic of any kind, because it will cut off all air around the tree. Add an inch to the summer mulch over the roots of the tree.
Problems of Larch
Surface Roots Appear At Base Of Tree
The European Larch is vulnerable to compacted soils and will produce surface roots in that environment. For solutions see the file Dealing With Surface Roots in www.yardener.com.
Larch Fails to Thrive
Too Much Shade - Larches, like most trees, need many hours of sun per day to thrive. Take care that neighboring plantings have not grown to block the exposure of young larch trees to the sun.
Needles Curled and Distorted
Aphids - Woolly larch aphids are soft-bodied, pear-shaped sucking insects, about the size of the head of a pin. They cluster on tree foliage and suck cell fluids, retarding or distorting tree growth. Needles may turn yellow or brown or sometimes curl and pucker.
Leaves Browned in Spring
Larch Casebearer. - One of the most serious pests of larches, this small black-headed caterpillar enters larch needles through a hole that it chews in the end or middle of the needle. It then tunnels, or mines, into the needle as it feeds during the late summer. In the fall it cuts the needle in half, forming a 1/4 inch long case that hangs from the twigs in which it over winters. To kill over wintering pests, spray the visible egg cases with lime sulfur or dormant oil to kill them before leaves emerge.
Needles Notched, Stripped
Larch Sawfly - These sawflies are larvae of small, wasp-like flies. They are worms that are 3/4 to 1 inch long, olive-green and covered with brown spines. They hatch from eggs laid in cuts in larch twigs in late spring and feed on larch needles, causing them to fall to the ground and rapidly stripping twigs bare. Heavy infestations will defoliate a tree.
Needles Consumed, Visible Tawny Egg Masses
Gypsy Moth Caterpillar - Larvae of the gypsy moth sometimes mass on larch foliage and devour it, defoliating the tree. The tree may die after repeated defoliations. Newly hatched caterpillars are about 1/16 inch long, and grow to about 2 1/2 inches. When mature they have 5 pairs of blue spots and 6 pairs of red spots along the back. Adult male moths have a wingspan of 1-1/2 inches, are light tan to dark brown, with blackish wavy bands across the forewings. The female moths are larger, nearly white, with 2 1/2 inch wings. They do not fly. They do lay masses of eggs, from 400 to 500, covered with velvety, buff-colored hairs which become caterpillars.
Branches and Stems Girdled, Resin Visible
Canker - Several kinds of fungi cause canker disease in larches. Typically cankers, or swellings, develop on branches and stems of trees. Stimulated by spores that enter the bark through injuries and destroy the inner tissue, these cankers develop gradually, leaking resin and causing severe distortion of the tree. Eventually affected limbs die. A specific form of canker that attacks European larches spawns ¼-inch hairy, white cup-shaped fruiting bodies that develop in the cankered tissue. Control of canker is very difficult. Prune away infected stems and branches promptly. Burn them or put them in the trash to avoid spreading the disease. Limit further outbreaks by maintaining tree vigor. Water, feed and protect trees as recommended above. Japanese larches are resistant to canker.
Needles Yellowed, Undersides Show Fungus
Rust - Several kinds of fungi cause rust on larch needles. One rust develops on nearby willows and then affects larches, another rust requires poplars as its alternate hosts. These fungi affect the tender young needles at the tips of branches. Their undersides become coated with pale yellow pustules and they turn yellow then brown and die. If the affected larch tree is the valued ornamental tree in the landscape, remove the alternate host of the rust to interrupt the life cycle of the fungi. Be absolutely sure that the problem is rust before cutting down the suspected host tree.
