To say that a tree is only useful for its nitrogen-fixing capacity is still to call that tree quite useful in a gardener’s eyes. Add to that talent the rich, buttery yellow heartwood of the aptly named American yellowwood, plus a potential for some very interesting dyes, and foot long chains of white flowers in the early summer, and this becomes a cool tree indeed.
Naturally rare, Yellowwood (Cladrastis kentuckea) is native only to the limestone cliffs of Kentucky and its neighbors, but the tree is willing to grow in a huge range of soil types and pH balances. It even survives winters fairly north of “home”, making it a darling of landscape designers. We like it all the more when we are tired of Zelkova (Yellowwood is similarly vase shaped and similarly mid-sized) and hoping for something less completely foreign to our ecology than laburnum. (Truth be told: Yellowwood won’t bloom for you every year. The years it blooms, it’s awesome, but other years it just rides the bench.)
Yellowwood is cousin to my other favorite summer-herald, the black locust tree (Robinia pseudoacacia). Unlike black locust, though, yellowwood is a medium to slow grower. You’d think with the extra time it takes, it could manage a decent branching angle, but alas. Beware the included bark, my friend, and too many branches from one juncture.
Like black locust, it burns fairly hot (locust still wins) and it’s willing to sprout from cuts, but that slowed growth rate makes it a poor coppice option.
More interesting to me is the urban potential for Yellowwood. As increased species diversity becomes more and more the mandate for cities and towns across the country, Yellowwood has some interesting mix and match capacities with other popular “trees about town”.
The compound leaf and the seed pod both look like smaller versions of the Kentucky coffeetree (until you look close and realize the Yellowwood is alternately pinnate!) The smooth grey bark is less showy than the Zelkova’s but not out of range, and a very good pairing indeed with many beech varieties. The fall color is akin to that of hickory and other not-ostentacious yellows. In short, pick the season or experience where you want your uniformity, and let the rest of the year undulate in the spice-y variety of life.