Deadheading conserves resources that would otherwise sustain production of seed. For species that bloom more than once, it promotes continued bloom. For others, it promotes healthier vegetative growth. Also, it inhibits proliferation of potentially invasive seed. It is neater anyway. However, several species might forego deadheading for seed collection.

Flowers that bloom only once for a brief season generate all their seed at the same time. Flowers that bloom for an extensive season generate seed for a more extensive season. Some seed is obtainable from ripe fruit. Some is obtainable from unharvested vegetable plants that go to seed. Seed collection involves various sources during various seasons.

Regardless of its season and source, most seed is too abundant for complete collection. A single fruiting vegetable, such as a true to type chile, provides more than enough seed. A few stalks of naked lady might provide more seed than one garden can accommodate. Wildflowers are an exception. Their seed collection is rarely too excessive to broadcast.

Many species do not reliably generate viable seed though. Some require pollination by a very specific pollinator that does not live here. Yuccas that are from Central America rely on moths that live only in Central America. Some bamboos generate seed only once in a century or so. Most hybrids are too genetically dysfunctional to produce any viable seed.

Hybrids that can generate viable seed are very unlikely true to type. In other words, their progeny will be very different from them. Such progeny tend to revert to a simpler or more primitive form. The same applies to progeny of cultivars of extensive breeding within one species. Genetic aberration, such as variegation, is likewise unlikely inheritable by seed.

To complicate seed collection, some species begin life with juvenile growth. Some might take several years to mature. Avocado seedlings initially grow very fast, and tall, without blooming. By the time they mature, bloom and produce fruit, such fruit can be too high to harvest. Trees from nurseries are fruitful lower only because of grafting with adult growth.