Seed Germination and Seedling Growth of Guaiacum sanctum, L.

Alexander, Taylor

INTRODUCTION: The native lignumvitae, Guaiacum sanctum L., has many desirable features as a small ornamental tree or shrub and was listed by Ruehle ( 4) as a potential ornamental plant for south Florida. It has evergreen compact foliage, abundant blue flowers usually in the spring and fall, clusters of opened fruits displaying bright red arils against an orange ovary wall, and a good natural growth form that can be modified by pruning. It has drought resistance and a broad tolerance to light conditions. It is also in need of conservation as it is facing extinction in the wild. Several specimens on the Florida Keys and in Dade County yards have been under surveillance a number of years as a part of an ecology project. In spite of very large seed crops, seedlings were found to be scarce under natural conditions and in yards. Casual attempts to germinate seeds were failures. These were followed without much success using the common techniques for breaking dormancy, such as temperature extremes, water soaking, and mechanical and acid scarification. A literature search revealed that Marreo (3), working with Guaiacum officinale, found that freshly harvested seeds germinated 9% in about 20 days. After one month of storage the figure rose to 20%, but in three months fell to 10%. These data on a second species supported the suspicion that a dormancy problem exists in this tropical genus. Slow growth of seedlings under natural conditions also presents a horticultural problem. A series of experiments and tests were conducted over a two-year period to determine how to germinate a high percentage of the seeds and to increase the growth rate of seedlings.