Picking flowers, or deadheading, can make some flowering plants produce new blooms. In simplistic terms, picking the flowers sends chemical signals to the plant telling it that it needs more blooms.

Another possibility, on some plants (and especially on young, newly planted/unestablished plants), is that it can redirect the energy, that the plant would otherwise put into producing fruit, back into growth/establishment.

For some monocarpous plants it can keep the plant alive for another season.

Quite common to do, too, if you want the energy to go into the growing of the plant (instead of into flowering).

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As soon as that flower stalk of this Haworthia was long enough, I removed it - the flowers are insignificant - what's attractive (to me, anyway) is the body.

So now I know which goddess to make offerings to for fruitful growth on my plants. Thanks!

davidhoffmanmusic, "A plant behaves as if it is the last one of its kind on earth; and its sole mission is to reproduce and keep the species from extinction. For those plants which must flower and set fruit/seed to accomplish this, plucking the flowers before the fruit/seed stage causes the plant to "panic" and set even more flowers to compensate". That is the story they told me and I am sticking to it because I have found it to be credible from experience. Further, if flowers are allowed to mature the plant says to itself, 'Mission Accomplished' and is content to lie down and die; hence the practice of dead heading to forestall this event.
Growers of vegetables know that if they pick the produce often and at the earliest acceptable stage, the plant becomes a gift that keeps on giving. A very good example of this is the ochro - Abelmoschus esculentus.
Apparently the fruit stalk contains the life or death triggering mechanism. If these are left on the mother plant it will decline. My grandmother would meticulously remove any such stalks that we would leave after picking any fruits in her kitchen garden.
(http://www.agriculture.gov.gy/Farmers%20Manual/PDF/Ochro.pdf)

When I was a kid, I was told that picking flowers would keep the plants blooming longer. I tried it with violets, but they stopped flowering just the same. I didn't know then that the violets also produce cleistogamous (closed) flowers that are self-pollinating.

Years later I picked spent flowers from the beautiful, blue-flowered Phacelia campanulata. The plants kept right on growing and blooming until they became infested with leaf-eating caterpillars and I had to destroy them. Wild specimens of the species (I found some a few blocks from my home) grew only a 5-6 inches tall, produced a cluster of blooms then died. Mission accomplished indeed.

This old gardening trick won't always work, especially with perennials that are seasonal bloomers (e.g., sensitive to photoperiod).

Karl