Sourwood (Oxydendrum arboreum) is one of our most beautiful U.S. native trees. Trees often grow multi-stemmed or shrub-like to 20-30 feet or in tree form to 35-40 feet high and narrow in spread. Trying to establish a new tree can be challenging.
In the wild sourwoods are often found growing in shallow soils on steep craggy mountainsides. They are a pioneering species. Tiny dehiscent seeds are dispersed into the wind and blown, like dust, from established trees over many acres of land. Tens of thousands of seedlings may germinate but few may survive. In Tennessee I have seen new seedlings prospering on cleared reclamation sites where soils are poor.
For a home gardener the challenge is to get this finicky species to survive its initial two years. Site them in the type of soil and environmental conditions which rhododendrons and mountain laurels enjoy. Newly-planted sourwoods tend to prioritize by establishing its root system first. New shoot growth may be slow.
Sourwood should be planted in late winter to early spring before leaf out. Plant in a well-drained moderately acidic (5.5 to 6.5 pH) soil. Prune back the new tree to 1 – 2 feet from the ground at planting. Essentially, you are starting over with 100% root system and 10-15% top growth. Within 2 months one or more root suckers may sprout and this will be your new sourwood. Select 1-3 of the most vigorous shhots and eliminate all others. Feed with 10-10-10 or equivalent granular fertilizer and irrigate during long dry periods.
In nature sourwoods seem to prefer the eastern facing slope in an open woodland area where they receive midday sun. Young transplants respond to fertilizing; older well-established trees do not. Sourwoods need some pruning, mostly to develop the tree’s framework. They have few serious insect or disease problems. Purple spotting on leaves is common in early autumn, but causes little injury.
Finding a nursery grown tree for sale is rare and many sellers will not guarantee them. Some on-line nurseries do list them.