Flowering trees come in many different types, often with white or pastel-colored blossoms in spring, but the golden chain tree (Laburnum anagyroides) has some unusual features. It blooms in early to midsummer, a bit later than many trees, and its flowers are a deep, bright yellow, an unusual and striking color in a flowering tree.
The golden chain tree, also called golden rain tree, gets its name from its long clusters of yellow flowers that hang down from its branches and resemble chains. A deciduous tree, it's a slow-to-moderate grower, adding about 1 foot or slightly more to its height each year. At maturity, the tree reaches 15 to 25 feet tall, depending on the conditions under which it grows. It has a generally upright growth habit, with a softly columnar shape when young. As it matures, the tree tends to widen its shape and eventually spreads out to become 9 to 12 feet wide.
2. Climate and Sun
The golden chain tree is quite hardy and grows in U.S. Department of Agriculture 5 through 7, where winter temperatures can fall below 0 degrees Fahrenheit. A native of central Europe, the tree is sensitive to extreme heat and doesn't do well areas above USDA zone 7, where summer heat can exceed 90 F for long periods and may be above 100 F. It grows well and performs best in regions where both summer and winter temperatures are moderate, without long periods of extreme heat or cold. Although it can grow well in full sun, a spot where it gets morning sun, followed by partial shade in the afternoon, is best in areas with hot summer sun.
3. Controlling Size
Although the golden chain tree has a naturally pleasing form, you can prune a young tree to help develop its shape and control its size. This is best done in winter, while the tree is dormant. To promote a bushy shape and keep the tree's size within bounds, cut back each branch by about one-third, making cuts just beyond an outward-facing bud to stimulate new growth that widens the tree's form without greatly increasing its height. If you prefer a more narrow, columnar shape, make cuts just ahead of buds that face slightly inwards, but remove any new growth that crosses or rubs against existing branches.
4. Other Requirements
The seeds and all parts of the golden chain tree are poisonous, so think carefully before planting it. The golden chain tree grows well when it receives regular watering during its first season or two, because this promotes a deep and extensive root system. Once established, it rarely needs extra water except during long dry spells or prolonged drought. It tolerates any type of well-drained soil, but prefers an organically rich loam. Adding compost to the planting site can help increase your soil's organic content and fertility. The tree grows poorly in wet, soggy areas, so if your soil is rich in clay and drains poorly, add some find sand at planting to improve its drainage.