One of the most common plants found in our landscapes are Indian Hawthorn (Raphiolepis indica). These evergreen low growing shrubs are used extensively in groupings or as border plants. Listed as drought tolerant by most regulatory agencies, their use has intensified by designers needing to meet landscape codes requiring a certain percentage of plants be drought tolerant. Native to southern China, they are both salt and shade tolerant making them even more useful in our coastal areas. With the introduction of the variety "indica Alba," the low growing compact form used today, from California in the 1980's, they have become one of the most widely used landscape plants.
Like many other new plant varieties introduced from other parts of the country, Indian Hawthorn has several major problems when planted in Florida's wet humid climate. They are highly susceptible to fungal leaf spot diseases, root rot diseases and nematodes resulting in a shortened useful lifespan of only 5-10 years.
Leaf spots don't kill the plant but are aesthetically unpleasing. Leaf spot can be controlled with repeated fungicide applications, but most fungicide labels recommend 2 - 4 week application intervals making the cost exceed the value of the plants. Overhead irrigation and rainfall, both of which are plentiful in Florida, are the reason leaf spots are so severe on these plants.
The most damaging problems, root rot and nematodes, are virtually impossible to control. Symptoms include canopy thinning, decreased growth, loss of vigor and eventual death. Usually a few plants in a grouping will start to show these symptoms as seen in the photo below. The decline eventually spreads to the remaining plants and the entire bed must be replaced. As the first few plants decline, homeowners usually replace them only to have the rest die. This cycle is frustrating as the new plants then decline and that investment is lost.
Picture 1. Declining and Healthy Plants
Nematodes are microscopic worm like organisms found in soil all over the world. They feed and damage roots resulting in a loss of water and nutrient uptake and providing an entrance for soil borne pathogens. There are no proven effective materials registered for nematode control in landscapes. The best defense is to plant nematode resistant plants. For more information on nematodes, here is a University of Florida website: http://edis.ifas.ufl.edu/in469.
Root inspections of these week plants reveals rotted, stunted and decayed roots with little or no fine root hairs responsible for water and nutrient uptake. These plants pull up easily from the soil. The picture below shows how these roots appear.
Picture 2. Damaged Root Systems
Our recommendation is to replace the Indian Hawthorn with plants better adapted to our climate. There are several new plant varieties having the same low growing habit as Indian Hawthorn that don't appear to have the same problems. As with all new plants, actual long term field observations often reveal deficiencies not found in nursery production.