The optimal harvest time is reached when you can collect large amounts of viable and germinable seeds. In this case, few seeds or fruits have been lost to predation, dispersal, or deterioration. You can monitor your species, create a field form, and group your species into 3 categories:
- Species with more or less continuous reproduction throughout the year, but often with 1 or 2 peaks. These species, typical of non-seasonal climates, have the advantage that some seeds are usually available at any time of the year, but the disadvantage is that only a small number of seeds can be collected at each harvest. They may remain viable on the tree for some time, but are often continually removed by dispersal. Often, you may find optimal quantity and quality during the peak seasons.
- Species with a defined fruit or seed ripening season, which typically have a short, early dispersal, frequent predation, and/or a short physiological viability. These are common in seasonal climates, especially in temperate zones. The seed collection must be very well planned since the seeds are easily and quickly lost, in a matter of hours or days. Premature harvesting of these species produces poor quality seed, while late harvesting produces little and aged seed collection. Both scenarios could threaten the seeds’ viability and storage potential or longevity. The timing of how fruits mature and disperse their seeds is generally influenced by local climatic conditions during the fruit maturation period. For instance, relatively cool, wet weather can delay ripening and dispersal for several weeks. Conversely, a sudden hot, dry spell can prompt fruits to open up and disperse their seeds. Such events can be extremely crucial in species where seeds disperse quickly after fruits become mature, such as those of many species of the Fabaceae family (please click here for further details).
In seasonal equatorial climates, where recalcitrant species are more common, collection timing is crucial. Because recalcitrant seeds’ embryos tend to continue developing until full seed maturity, early harvesting may threaten embryo and seed viability. Because recalcitrant seeds do not tolerate desiccation, and therefore do not stay viable for very long, late harvesting is also usually unsuitable.
- Species with a defined fruit or seed ripening season, but which remain on the plant for a long time before dispersal. These are also common in seasonal and temperate climates. Due to their characteristics, these species facilitate seed handling because the collection time is not as critical. However, it is still important to monitor them since they often suffer from predation and damage by weevils and other insects, and if left too long on the mother plant, they will age, losing viability and potential longevity in storage. In species with dehiscent fruits (those that open naturally to release seeds), delayed seed collection can result in poor seed harvest, as most seeds might be already dispersed, and only empty fruits remain on the trees.