52 
Newsletter of the Hawaiian Botanical Society 
Breaking Seed Dormancy in Hawaiian 
Santalum Species with Gibberellic Acid 
Bruce P. Koebele 
84-688 Ala Mahiku drive #157B,Wai'anae, HI 96792 
It started as a rather straightforward project for 
the Nature Conservancy of Hawai'i - develop a 
reliable means of germinating Santalum 
freycinetianum var. lanaiense seeds. I had 
repeatedly germinated S. ellipticum seeds in a tray 
of clean vermiculite after first scarifying the apex 
of the fruit's endocarp and then soaking the 
endocarp (containing the seed) in tap water for one 
to two days. These seeds usually took five to eight 
weeds to sprout and germination percentages were 
nearly always 80% or better. However, after more 
than 200 seeds and seven months with a variety of 
pretreatments including scarifying the endocarp, 
cracking the endocarp, removing the endocarp and 
soaking from one day to two weeks in tap water, I 
still had less than a handful of S. freycinetianum 
var. lanaiense seeds that had germinated. Of these 
few, none had survived and grown into healthy 
seedlings. Frustrated, I turned to the literature for 
help. In the USDA Forest Service General 
Technical Report PSW-122. 1990 (Sandalwood in 
the Pacific: A State of Knowledge Synthesis and 
Summary from the April 1990 Symposium), the 
Centre Technique Forestier Tropical (CTFT) in 
New Caledonia reported a "very efficient 
technique" they developed "which involves pre- 
soaking with GA..." The report did not state 
which Santalum species the CTFT tested with this 
technique. However, the non-Hawaiian species, S. 
album, S. austrocaledonicum and S. spicatum are 
referred to in connection with other research 
conducted by the CTFT. 
The gibberellic acid worked. Not only did 
gibberellic acid prompt the germination of S. 
freycinetianum var. lanaiense seeds but it 
dramatically sped up the germination of S. 
ellipticum seeds as well. (I have not tested S. 
paniculatum). Gibberellic acid can be purchased 
from a biological supply company such as 
Carolina Biological Supply, Inc. Unfortunately, 
the small amounts needed require a sensitive scale 
for weighing but resourceful growers should be 
able to overcome this inconvenience. 
Begin by extracting the endocarp (containing a 
seed) from a ripe fruit and cleaning it by hand 
underwater. Let the endocarp-seed air dry for 
approximately one week. Then, using forceps or 
medium sandpaper, remove a small portion of the 
endocarp at its pointed end (apex) so that the 
embryo inside is visible; do not damage the 
embryo. Soak the endocarp-seed in a shallow 
container of 0.05% gibberellic acid for five days, 
changing the solution daily. Afterward, remove 
the endocarp-seed from the gibberellic acid 
solution and dust it with a 1 : 1 mixture of powdered 
sulfur and captan®. This will inhibit fungus from 
infecting the seed. Sow the endocarp-seed in a 
covered tray on new moist vermiculite. 
Seeds begin sprouting in about one week and 
continue to germinate for another two to three 
weeks. Watch for a crack to develop in the thick 
endocarp. The crack's interior, the embryo, looks 
white against the dark endocarp. As the crack 
widens, the root emerges from the embryo's apex. 
After good root development (an additional one to 
two weeks), transfer the seedlings to individual 
containers containing a 1 : 1 mix of fine cinder (not 
black sand) and vermiculite. Using a peat-based 
medium caused some seed and seedling death by 
fungal infection. Germination using this method is 
over 90% successful for the two species tested. 
Even endocarp-seeds as old as seven months 
responded to the above treatment and sprouted at a 
high percentage. 
