The Sour Gum is a stately, deciduous tree of the eastern forests that has glossy, dark green leaves and edible, dark blue fruits. It is primarily a lowland tree found in low wet woods, bottomlands and pond margins, but also can be found on dry rocky wooded slopes and ravines. It has a straight trunk and rounded crown (more pyramidal when young) that typically grows 30-50' tall, but occasionally to 90'. Primarily dioecious (separate male and female trees), but each tree often has some perfect flowers. Small, greenish-white flowers appear in spring on long stalks (female flowers in sparse clusters and male flowers in dense heads). Although flowers are not showy, they are an excellent nectar source for bees. Flowers give way to oval, 1/2" long fruits which are technically edible but quite sour (hence the common name). Fruits mature to a dark blue and are attractive to birds and wildlife. Spectacular scarlet fall color. Obovate to elliptic, entire to slightly toothed leaves (to 5" long) are dark green above and paler below. It is also known as the black gum and the sour gum. Tolerates poorly-drained soils and can grow in standing water. On the other end of the spectrum, tolerates some drought and adapts to some dryish soils, at least in the wild. Long taproot precludes moving established trees. Female trees need a male pollinator to set fruit. Excellent ornamental shade tree for lawns or street tree. Also grows well in moist woodland gardens or naturalized areas or in low spots subject to periodic flooding or in boggy areas. Although slow-growing, it still needs to be sited in an area which affords plenty of room for future growth, particularly since it is so difficult to transplant. Easily grown in average, medium to wet soils in full sun to part shade. Prefers moist, acidic soils. Hardy in zones 3-9.
Growing Instructions for the Sour Gum
The seeds have a period of dormancy. They can be planted outdoors in the fall or winter for spring germination or they can be cold stratified to simulate winter conditions and to break their dormancy at any time of the year. 1. Soak the seeds in water for 24 hours. 2. Put the seeds in a ziplock bag. 3. Put the bag in the refrigerator for 2 months. 4. The seeds like moist soil. Prepare a mixture of half potting soil and half sand, perlite or vermiculite. Put the soil in a pot. 5. Sow the seeds on the soil. 6. Cover the seeds with a thin layer of soil. 7. Water the soil. 8. When the seedlings are a few inches tall, they can be transplanted.