Laburnum trees are spectacularly showy trees desirable for their large clusters of hanging yellow flowers. For this reason, they are also called golden-chain or golden-rain trees. The most commonly cultivated species is L. watereri, according to the USDA Forest Service. When two trees grow opposite each other and are trained along an arch, the end result is a gorgeous overhead display. Some botanical gardens set several arches next to one another, creating a flowering walkway. These are called Laburnum walks or arches.
Grow each tree in very well-draining, rich, alkaline soil. The trees grow best in soil that has a pH level above 7.0.
Plant in a location that is exposed to only partial sunlight. These trees do not do well in bright, hot sun and should be sheltered from direct afternoon sunlight. Because they are on the small side (they average about 15 feet tall when growing straight), you can plant laburnum trees under other, larger trees in dappled shade.
Plant the trees opposite each other on either side of an arch. An arch that is 8 feet tall works well and will be easily covered by the tree. You can also choose to grow just one tree on one side of the arch, but it will take longer for the arch to be completely covered.
Keep the soil moist and cool, but never waterlogged. Overly wet soil will lead to root rot. Underplanting (planting around the tree) with small bulb flowers such as hyacinths and crocuses will help stifle weed growth and keep the soil cool.
Train the tree so that it will grow over the arch. Carefully fasten new shoots to the arch with floral wire or string. Prune away branches that are growing the wrong way in late winter, before new growth appears in the spring.
This tree does not tolerate hot weather and grows best in U.S. Department of Agriculture plant hardiness zones 5 through 7.