Best suited for drought-tolerant gardens in mild winter climates, Mexican bird of paradise (Caesalpinia mexicana) forms a large shrub or small evergreen tree which reaches 10 to 25 feet tall and 6 to 18 feet wide. Hardy in U.S. Department of Agriculture plant hardiness zones 10b through 11, it's suitable for small spaces, growing well in patios, side yards, or areas near walks or parking lots. Clusters of bright yellow flowers occur at branch ends in warm months, sometimes from spring to fall. The seeds are poisonous if eaten.
Light and Soil Conditions
Mexican bird of paradise grows best and has more flowers in full sun but will tolerate partial shade. Native to washes and hillsides in southern Texas and northern Mexico, plants thrive on heat and in most well-drained soil types.
If you're growing Mexican bird of paradise as a specimen plant, leave enough room around it for it to grow to its average size, which is about 10 feet tall and 6 feet wide. It can get larger in favorable circumstances, but you can keep it to size through occasional trimming. Locate plants at least 10 feet away from buildings, structures or other plants. For hedges or screening, plant Mexican bird of paradise 5 to 6 feet apart.
Young plants need regular watering for the first year they're in the landscape to establish good root systems. Water the plants during their first spring, fall and summer whenever the top 1 to 2 inches of soil becomes dry, soaking the root area. In cool summer areas, plants don't need much supplemental water. In areas with hot, dry summers, water the plants occasionally. The University of Arizona Extension suggests watering plants in southern Arizona once a week during the summer when they're flowering.
Even in mild winter climates, occasionally temperatures can fall below freezing. Mexican bird of paradise is damaged or killed back when temperatures approach 20 degrees Fahrenheit or below. Cover the plant with a frost blanket or sheets when hard freezes are predicted. Hold the fabric off the foliage with a framework. If dieback occurs, the plants regrow from stem or branch bases. Wait until spring to cut away dead plant parts so you can tell how far to cut back to living tissue. Shape and even out the growth as the plant fills back in. Clean pruning tools with a cloth soaked in rubbing alcohol before and after pruning.
Caesalpinias are in the bean family and can harvest their own nitrogen from the environment with the aid of nitrogen-fixing bacteria on their roots. During spring and summer, fertilize monthly with a low nitrogen fertilizer such as 0-10-10 at the rate of 2 tablespoons per foot of plant height. Scatter the fertilizer on top of the soil around the Mexican bird of paradise, mix it into the top layer of soil, and water the plant thoroughly. Stop fertilizing in late summer to prevent tender new growth when frosts might occur.