Best grown in moist, acidic, well-drained soils in full sun. Tolerates some light shade. Intolerant of full shade, dry soils and most city pollutants. Best performance is in temperature conditions that mirror its native habitat, namely, cool summers and cold winters. Trees perform poorly in hot and humid summer conditions south of USDA Zone 5 including the St. Louis area.
Tamarack, also commonly called Eastern larch, American larch or hackmatack, is a deciduous conifer whose green needles turn a showy yellow in fall before falling to the ground as winter approaches. This is a tree of very cold climates, growing to the tree line across North America. It is native to boggy soils, wet poorly-drained woodlands and some moist upland soils primarily in the boreal forests from central Alaska, Yukon Territories and British Columbia to Newfoundland dipping south to Minnesota, Illinois and Pennsylvania. This is a medium to large sized tree that typically grows to 40-60' (less frequently to 80’) tall with an open pyramidal shape and horizontal branching. Slender green needles (to 1 1/4" long) grow in brush-like clusters (up to 30 needles per cluster) which appear at the ends of short spur-like shoots spaced along the branches. Rounded cones (to 1”) mature to brown. Bark on mature trees is a scaly, reddish-brown.
Other deciduous conifers include dawn redwood (Metasequoia glyptostroboises), bald cypress (Taxodium distichum) and ginkgo (Ginkgo biloba).
Potential insect pests include larch case-bearer, larch sawfly, larch looper, tussock moth, Japanese beetle and woolly aphids. Potential disease problems include needle cast, needle rust and canker.
Tamarack is grown in cold areas, and is not recommended for the St. Louis climate. It is often grown in groups. Good fall color.
Information gathered from: http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=284985&isprofile=1&basic=tamarack