Cold hardy, compact and shade tolerant, the windmill palm (Trachycarpus fortunei) is a surprisingly tough, versatile tree. The palm grows to an average height between 20 to 40 feet, producing a lush, symmetrical crown up to 10 feet wide. With proper maintenance and care, the windmill palm can be grown in a wide range of growing conditions.
Windmill palm is among one of the most frost-tolerant palms available and is hardy in U.S. Department of Agriculture plant hardiness zones 7 to 10. Mature trees can generally survive temperatures as low as 10 degrees Fahrenheit, according to the Missouri Botanical Garden. If temperatures approach single digits, however, windmill palm can benefit from winter protection. Cover and secure the palm's crown with a plastic sheet and apply a thin layer of organic mulch around the base of the palm, keeping the mulch from actually touching the trunk.
Location, Location, Location
Windmill palm will look its best in partial or even full shade. In the cooler end of its hardiness zones, windmill palm will tolerate full sunlight if the soil is kept consistently moist. The palm's crown will generally be more compact in sunny situations. Windmill palm is moderately tolerant of salt and wind and can be planted close to the seashore, although the fronds will get ragged in especially windy, exposed locations. A location with some wind protection, such as behind a sand dune or near a building, is ideal.
Windmill palm is slow growing and can benefit from regular irrigation. Water enough to keep the soil moist, but not waterlogged. Although drought tolerant, windmill palm will become stunted during long dry periods. The palm prefers fertile, well-draining soil, although it will survive in just about all soil types except compacted, consistently flooded soil. If planting multiple palms, space plants 6 to 10 feet apart to prevent competition for nutrients and water and to provide ample air circulation.
To boost growth rate and increase health, fertilize your windmill palm with a slow-release 10-10-10 fertilizer. The Seminole County Extension Service recommends fertilizing palms monthly with 1/2 to 2 pounds of fertilizer per month during the growing season, with mature palms getting more fertilizer and young palms getting less. Apply fertilizer around the soil under the canopy, taking care not to place fertilizer directly against the trunk. Follow label instructions exactly, and water well before applying to keep from burning the roots. Windmill palm has no serious disease or insect problems, notes Missouri Botanical Garden.