Horticulture Digest #107
PALM SEED GERMINATION

• Seed Collection
• Preplant Treatments
• Postplant Treatments
• Transplanting
• Summary

The production of indoor tropical foliage plants in Hawaii has increased significantly over the past 20 years. This growth peaked in 1990 with a wholesale value of $14.6 million with about 30% of this production in palms.

Palms are generally slow growing, but the growing conditions found in Hawaii give our growers an advantage with year round growing conditions. Palms are generally propagated from seeds, but growers have reported that many palm species are slow to ge rminate or are irregular in their germination pattern. This is a summary of some of the observations and research findings relative to palm seed germination at the University of Hawaii.

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Seed Collection

It is generally recommended to collect mature seeds from the tree, as those collected from the ground are often infested with seed weevils. Maturity is indicated by a color change, usually from green to that appropriate for the species (red, yellow, black, etc.). Most palm seeds have a short storage life, so they should be planted when fresh.

We also recommend removal of the fleshy seed coat, as it often contains a germination inhibitor, unless you have had experience with the species. The seed coat effect is illustrated in Table 1 which shows a difference between 2 species of Pritcha rdia (Yoshii & Rauch, 1989a). T50 is a measure of how long it takes 50% of the seeds to germinate (Orchard, 1977).

Table 1.  The effect of seed coat removal on germination 
of palm seeds.

                                           Final
Treatment                     T50       germination
                             (wks)       (percent)

Pritchardia hildebrandi
     With                     7.6           90
     Without                  1.9           76

Pritchardia thurstonii
     With                     2.9           96
     Without                  2.1           96

We tried a simple bioassay of the seed coat of areca palm (Chrysalidocarpus lutescens) by removing the fleshy pericarp, macerating the pulp in a blender, and filtering through a cheesecloth and then filter paper (Rauch & Crivellone, 1989). This so lution was used to germinate lettuce seeds compared to seeds watered with deionized water (Table 2). Clearly, the solution derived from the palm fruit pericarp inhibited germination of the lettuce seed.

Table 2.  Bioassay test of areca palm seed pericarp 
solution.

Days     Lettuce seed germination percentage
           Water control  Pericarp solution

1              86.7               0
2              89.3               0
7              91.3               0

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Preplant Treatments

There have been a number of other preplant seed treatments proposed to improve the germination of palm seeds, such as soaking in water with or without chemicals. In earlier trials, we found that presoaking the seeds in water or gibberellic acid (GA) solu tions increased the germination percent of areca palms (Rauch, Schmidt & Murakami, 1982). However, with bamboo palm (Chamaedorea seifrizii), the water soak proved beneficial, but there was no response to the GA treatment (Table 3) (Yoshii, Rauch & Okazaki, 1989).

Our current recommendation is to soak the cleaned palm seeds in water for 3 days prior to planting, changing the water each day.

Table 3.  The effect of water and 48 hour GA pre-soak 
treatments on germination of Chamaedorea seifrizii 
seeds after 23 weeks.

                                           Final
Treatment                     T50       germination
                             (wks)       (percent)

Untreated control            11.1 ab       67 a

24 hr water pre-soak         11.4 ab       52 a
48 hr water pre-soak         12.0 a        57 a
72 hr water pre-soak          9.8 b        56 a

100 ppm GA pre-soak          11.6 ab       72 a
1000 ppm GA pre-soak         10.8 ab       59 a
2000 ppm GA pre-soak         11.1 ab       59 a

Mean separation in columns by Duncan's multiple 
range test, 5% level.

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Postplant Treatments

There is very little information on the best medium for germinating palms. To date the results are somewhat mixed as germination was better in the well-drained cinder or perlite than peat moss as shown in Table 4 for the germination of Ptychosperma mac arthuri seeds.

Table 4.  The effect of media on germination of 
Ptychosperma macarthuri seeds after 14 weeks.

                                           Final
Treatment                     T50       germination
                             (wks)       (percent)

Cinder                        8.5 a        60 ab
Peat:cinder (1:1)             8.2 ab       35 c
Peat                          7.3 bc       46 bc
Peat:perlite (1:1)            7.1 c        32 c
Vermiculite                   7.0 c        56 ab
Perlite                       6.7 c        63 a
Perlite:vermiculite (1:1)     6.5 c        60 ab

Mean separation in columns by Duncan's multiple
range test, 5% level.

However, there was no difference due to the medium in the germination percent of Pritchardia thurstonii seeds in Table 5 (Yoshii & Rauch, 1989a).

Table 5.  The effect of media on germination of 
Pritchardia thurstonii seeds after 14 weeks.

                                           Final
Treatment                      T50      germination
                              (wks)      (percent)

Perlite                       3.1 a        97 ab
Cinder                        2.5 b        93 c
Vermiculite                   2.4 bc       97 abc
Perlite:vermiculite (1:1)     2.4 bc       94 bc
Peat                          2.3 bcd      98 a
Peat:perlite (1:1)            2.1 cd       98 a
Peat:cinder (1:1)             2.1 cd       96 abc

Mean separation in columns by Duncan's multiple 
range test, 5% level.

One of the more beneficial treatments for enhancing the germination of palm seeds is bottom heat (Donselman, 1982). The suggested medium temperature is 95 to 105°F. This is especially beneficial for slow to germinated seeds such as bamboo palm (Table 6). Germination can be reduced from 8 months to 8 weeks (Yoshii, Rauch & Okazaki, 1989).

Table 6.  Effect of medium temperature on germination 
of Chamaedorea seifrizii seeds after 20 weeks.

                                           Final
Temperature                   T50       germination
(+/- 1°C)                    (wks)       (percent)

Unheated control             0.0 a          0 b
25                           0.0 a          0 b
30                          10.8 b         60 a
35                           9.0 c         62 a

Mean separation in columns by Duncan's multiple 
range test, 5% level.

Areca palm seeds were germinated using a combination of the better treatments (Table 7). While most of the treatments proved beneficial in improving the germination rate, the best was a combination of water presoak and bottom heat (Yoshii & Rauch, 1989b). It should be pointed out that for the most part we have only been able to improve the rate of germination and not the germination percent.

Table 7.  The effect of temperature, water and GA 
combinations on germination of areca palm seeds 
Chrysalidocarpus lutescens Wendl. after 20 weeks.

                                            Final
Treatment                      T50       germination
                              (wks)       (percent)

Control-no treatment          6.4 a         94 ab
100 pm GA pre-soak            6.2 ab        89 b
Water pre-soak                6.1 bc        95 ab
Bottom heat                   5.8 c         93 ab
100 ppm GA pre-soak
  + bottom heat               5.4 d         95 ab
Water pre-soak + bottom heat  5.1 e         97 a

Mean separation in columns by Duncan's multiple 
range test, 5% level.

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Transplanting

In trials to determine the best time to transplant palm seedlings, we found that the spike or 1st leaf stage was best (Murakami & Rauch, 1984). This resulted in less transplant shock and plant loss.
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Summary

• Use fresh seeds harvested from the tree
• Remove fleshy seed coat
• Use preplant water soak treatment
• Plant shallow in a well-drained mix
• Use 95°F bottom heat
• Transplant at spike or 1st leaf stage.

Fred D. Rauch, rauch@hawaii.edu
Specialist in Horticulture

LITERATURE CITED

Donselman, H. 1982. Palm seed germination studies. Proc. Florida State Hort. Soc. 95: 256-257.

Murakami, P. K. and F. D. Rauch. 1984. The effect of age and handling on the subsequent growth and development of Chrysalidocarpus lutescens seedling. Jour. Envir. Hort. 2(3): 91-93.

Orchard, T. J. 1977. Estimating the parameters of plant seedling emergence. Seed Sci. Tech. 5:61-69. Rauch, F. D., L. Schmidt & P. K'. Murakami. 1982. Seed propagation of palms. Inter. Plant Prop. Soc. Proc. 43:341-347.

Rauch, F. D. & C. F. Crivellone. 1989. Palm seed inhibitor study. Hawaii Nursery Research. Univ. of Hawai'i Res. Ext. Series 103:27.

Yoshii, C. M. & F. D. Rauch. 1989a. The effect of media and seed cleaning on the germination of selected palm seed. Hawaii Nursery Research. Univ. of Hawai'i Res. Ext. Series 103:25-26.

Yoshii, C. M. & F. D. Rauch. 1989b. The influence of treatment combinations on areca palm seed germination. Hawaii Nursery Research. Univ. of Hawai'i Res. Ext. Series 103:22-23.

Yoshii, C. M., F. D. Rauch & C. I. Okazaki. 1989. Treatments influencing the germination of bamboo palm seeds. Hawaii Nursery Research. Univ. of Hawai'i Pres. Ext. Series 103:23-24.
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