Among the most cold hardy of trunked palms, the six species of windmill palms (Trachycarpus spp.) gain favor in warm temperate regions where winter temperatures typically drop no lower than the range of 5 to 15 degrees Fahrenheit. The fan-like fronds and copious production of black fruit seeds add a tropical feel to a landscape. Although they mature slowly to a height of 40 to 70 feet over many decades, windmill palms work nicely in courtyards and other "tight spaces," unlike much larger leaved palm species.
Select a planting site on your property that receives at least six hours of direct sunlight daily in a fertile but well-draining soil. Position it where cold, drying winds do not bombard it, especially in the winter. This is most important in U.S. Department of Agriculture hardiness zones 7 and 8.
Monitor the soil around the windmill palm year round. For best growth, keep the soil moist but never soggy. Supplement natural rainfall as needed so that during the growing season, about 1 to 2 inches of water reaches the palm's roots. Use a garden hose or sprinkling can to water the area extending 3 to 4 feet outwards from the trunk. In winter do not water; only allow natural rainfall to moisten the palm's roots.
Place a 3 to 4 inch layer or organic mulch over the root zone area of the windmill palm to help retain moisture and choke out weeds. Keep the mulch 6 inches away from the trunk itself, but extend the mulch out to at least 4 feet in all directions from the trunk. Replenish the mulch as needed each year as it decomposes and compresses in depth.
Fertilize with a slow-release well-balanced fertilizer once at the vernal equinox, again eight to 10 weeks later and lastly three weeks before the autumnal equinox. Follow product label directions for precise dosage recommendations for your size of windmill palm. Scatter the granules over the mulched area where the newest roots grow, just beyond the reach of the fronds. If you live in USDA hardiness zones 9 and 10, an additional and final fertilization can occur four weeks after the autumnal equinox.
Prune away dry, dead fronds with a hand pruners as needed. Allow yellowing fronds to remain on the palm so nutrients can be relocated to other parts of the plant. If you feel the flower stalks or fruits are bothersome, prune them off as they emerge in early summer. Only female-gendered windmill palms will bear fruits, and only if a male palm is nearby.
Gather and remove fallen fruits from the windmill palm, as they will germinate. These seedlings become weedy and pull out easily only when less than 4 inches tall, before their taproots get too strong.
Remove heavy, wet snow from the fronds in winter to prevent breakage. Consider tying up the fronds with twine in an erect tuft when a strong ice storm or heavy sleet is expected. This helps protect the growing tip from moisture and possible rot, if it freezes.