In article ,
ellieland wrote:

Hi i am not a gardener but i am a film maker making a film about leeks.
I know that leeks can also produce clones as well as seeds, but can
someone tell me if other plants do this? and why do some and not
others?

Innumerable other plants do this, by many different methods. Some,
like garlic, never produce seeds -- it's all asexual reproduction.
Many plants can be propagated asexually even if they seldom or never do
so on their own.

You can find out a lot of this in any introductory biology textbook.
As for why, every plant has its own strategy. Asexual methods are
often more reliable, but only sexual methods (seeding) provide the
genetic diversity necessary to withstand disease and changing
conditions in the long term. Of course, in domesticated plants, the
strategy is often modified to promote the gardener's rather than the
plant's agenda.

A factlet for your film: elephant garlic is actually a leek, not a
garlic.