The optimum time for seed collection is as soon as the seed is mature. For most types of trees, seed pods turn brown when the seed inside is mature. Pods begin falling to the ground when seed is ripe.
Some types, however, must be collected when pods are still on the branches. Some, like Grevillea robusta, have light seed bearing fruits which will open on the tree and allow seed to blow away. In other cases, seed will over-ripen and not germinate well or be susceptible to insect attack if fruits or pods stay on the tree too long. Neem and Acacia sp. are examples of this. In these cases, collection must be done when pods or fruits are still on the tree.
Seed of some species, like Combretum and Terminalia, appear brown even when unripe. Careful observation must be done to ensure that the seed inside the pods is mature before harvesting. Mature seed is usually brown. If the seed coat is opened when ripe, the seed inside will usually be light in color, and only slightly moist. Most seed pods will crack open when seeds are mature. Your ability to know when a seed is perfectly ripe will develop through observation and experience.
