It is always best to collect fruits at the point of natural dispersal to ensure high viability and longevity (see Section 4.1 of the Seed Collection textbook). However, sometimes it is possible to collect fruits slightly unripe, if it is not possible to return to the population at the right time or if the seeds are likely to be dispersed or predated by then.
Always perform a cut test on a few seeds to assess the ripening stage before collecting. If the seed’s final size is reached, the seed coat is hard, and the embryo and endosperm are well formed and distinguishable, you might want to try and collect the seeds.
Collect branches with fruits attached, and keep them in a ventilated warm and humid environment, both in the field and at the seed bank. For some species, it is possible to place the branches on a tray in a designated area in your seed bank or in the nursery, or even place the lower parts of the branches in a glass or container of water, to allow water uptake to the fruits. Monitor the ripening process daily, and make sure they do not develop any mold. When the fruits look mature, it is best to repeat the cut test on a few seeds to assess their ripening too.
If some fruits mature before others, it is recommended to process them first, leaving the others to mature further.
Not all species will be able to mature after being detached from the mother plant, so it is recommended to use these methods on a small quantity of seeds first. You will learn the best procedures for your species with experience. Always take notes during all steps, and keep the information together with the seed accession data. They will be useful in case of low viability or low desiccation tolerance.
If a species’ seeds cannot be ripened after removal from the mother plant, in some cases you can collect slightly immature seeds and sow them right away. At this stage they may be ripe enough to germinate and grow into plants, but keep in mind that immature seeds have not developed a full tolerance to desiccation, and therefore they may not be good candidates for storage.