Abstract
Burkea africana and Erythrophleum africanum are characterized by seed coat-imposed dormancy that prevents water entry and gaseous exchange, which are essential for the germination process. The objective of this study was to determine the best possible pre-sowing treatment method that maximizes seed germination of the two species. Seeds of both species were subjected to four experiments, containing 10 levels of presowing treatments: The control, mechanical scarification, soaking in concentrated sulphuric acid (for 15, 30, 45 and 60 min), immersion in boiling water (for 1, 3 and 5 min), and soaking in boiling water (and cooling down for 24 h). The germination data were subjected to ANOVA followed by Tukey’s HSD Test to separate significantly different treatment means. The most promising results showed that seeds treated with mechanical, sulphuric acid and boiling water scarification had significantly higher mean percent germination than the controls for B. africana; whereas for E. africanum, mechanical scarification, exposure to sulphuric acid, boiling water (1 min) and immersion in boiling water (and cooling down for 24 h) had higher percent germination than the controls. Key words: Burkea africana, Erythrophleum africanum, germination percentage, pre-sowing treatment, seed dormancy.  
Highlights
Over the past few years, Botswana has put considerable efforts into forest conservation and afforestation programmes, such as the annual national tree planting day
The results indicated that seeds treated with mechanical scarification, sulphuric acid and boiling water had significantly higher mean germination percentages than the control in B. africana [(One Way analysis of variance (ANOVA): (F (9, 39) = 15.86, P = 0.00001)]
The results showed that seeds of B. africana that were treated with sulphuric acid exhibited the fastest and uniform germination, reaching > 90% cumulative germination within five days after sowing, followed by mechanical scarification, reaching > 78% within 8 days and those treated with sulphuric acid, reaching > 71% and > 65% within seven days, respectively (Figure 1)
Summary
Over the past few years, Botswana has put considerable efforts into forest conservation and afforestation programmes, such as the annual national tree planting day. This day dates back to 1985 when the President Sir Ketumile Masire launched the first national tree planting day and has since been commemorated on the last Saturday of November each year (BOPA, 2013). At inception of the tree planting day, exotic tree species were planted in community woodlots and distributed for planting by individuals.
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