Mexican Heather (Cuphea hyssopifolia) is a popular ornamental plant known for its delicate appearance and abundant blooms. This compact, evergreen subshrub features small, bright green leaves and a continuous display of tiny flowers. Gardeners frequently use Mexican Heather as a groundcover, for borders, or as an attractive addition to containers and hanging baskets.
Understanding Mexican Heather’s Temperature Needs
Mexican Heather thrives in warm, tropical climates, with an ideal temperature range between 75-85°F (24-29°C). It is perennial in USDA Hardiness Zones 9 through 11. However, in areas with cooler winters, Mexican Heather is cultivated as an annual. It prefers temperatures above 55°F (13°C) for optimal growth.
Protecting Against Cold Temperatures
Mexican Heather is sensitive to cold, and even a light frost can cause significant damage. Temperatures at or below 32°F (0°C) can lead to wilting, browning of leaves, and dieback. If the soil freezes, the plant may not survive.
To protect Mexican Heather from cold snaps, consider applying a layer of mulch around the plant’s base. This helps insulate the soil and protect the roots from freezing. For container-grown plants, bringing them indoors to a warm, bright location before temperatures drop below 50°F (10°C) is an effective strategy.
If a brief frost is expected, covering outdoor plants with cardboard boxes or a plastic tub overnight can offer temporary protection, but remember to remove covers during the day. Watering plants before a frost can also help warm the soil. If some dieback occurs after cold exposure, pruning the plant back by about half in late winter or early spring can encourage dense, new growth.
Managing High Temperatures
Mexican Heather exhibits good tolerance for high summer heat. It prefers full sun, receiving six to eight hours of direct sunlight daily. However, in regions with intense afternoon heat, providing some partial shade can prevent the foliage from turning a lighter green or experiencing scorch. Signs of heat stress include wilting, yellowing foliage, and leaf scorch.
Adequate watering helps Mexican Heather manage high temperatures. While established plants can tolerate some drought, they perform best with regular moisture, especially during hot and dry periods. Water deeply at least once a week, or more frequently if the soil surface dries quickly, particularly for container plants. Watering in the morning allows the plant to absorb moisture before the day’s heat causes rapid evaporation. Ensuring good air circulation around the plants also helps dissipate heat and reduce stress.