Named for the highly textured maroon foliage, purple waffle plants (Hemigraphis "Exotica") add tropical flair as houseplants and can grow outdoors in U.S. Department of Agriculture plant hardiness zones 10 through 11. Once this relatively low-maintenance plant is established in a suitably bright, humid spot, regular care will help improve their appearance and increase their resistance to pest infestations.
Purple waffle plants require moderately moist soil year-round to keep their foliage lush and healthy. In summer, water whenever the soil feels barely damp 1/4 inch below the surface. Water deeply but infrequently, adding water until it trickles from the drainage holes at the base of the pot. In winter, the soil will take longer to dry out so water it less frequently. Monitor the soil moisture closely and water only when it has dried out 1/4 inch below the surface. Always use filtered or demineralized water when watering purple waffle plants to prevent the buildup of excess salts in the soil.
Overfertilizing purple waffle plants often causes weak, spindly growth that detracts from their naturally lush, vibrant appearance. Monthly feeding with a weak fertilizer solution during the growing season will help keep the plant growing vigorously -- especially if it is in a pot. Dilute 1 teaspoon of general purpose, 20-20-20 ratio fertilizer in 1 gallon of water. Replace one watering per month with the fertilizer solution, taking care not to splash any on the leaves. Purple waffle plants benefit from a rest period during the colder months, so stop feeding in fall to allow the plant to enter dormancy.
Pruning and Grooming
Purple waffle plants sometimes develop minor cosmetic issues. The most common issue is spindly or dead, damaged growth. Prune off the unwanted stems at the base whenever they appear. Before use, soak the pruning shears in undiluted household disinfectant for five minutes and rinse them thoroughly before you use them. Disinfecting the shears prevents the spread of disease. Purple waffle plants require high humidity and may develop leaves with crisp edges if the air is too dry. Daily misting will help correct the problem, as will regular watering. Use demineralized water to prevent white spots from showing up on the leaves.
Purple waffle plants suffer from few serious insect problems, although they may develop minor infestations of whiteflies and scale insects. The problems show on the undersides of the leaves, where cottony matter and honeydew sap often appear. Advanced infestations can cause leaf scorching and stem dieback. Treat scale or whitefly infestations with a ready-to-use insecticidal soap spray. Spray the solution on the tops and bottoms of the leaves every four to seven days until the bugs are gone. Rinse the leaves with clean water a few hours after each application to reduce the risk of injury. Follow the instructions on the label as they vary among brands.