How do plants know when to flower?

Some flower to schedule.

Some plants are programmed to flower automatically, regardless of other factors. These species are typically annuals.

Some must grow up first.

Many species pass from a juvenile phase into a mature phase, after which time they are able to flower.

Floral genes are activated.

There are many genes that need to be activated to enable flowering in all angiosperms.

Some can tell the time.

Some species have internal clocks that mean they will only flower at certain times of day or night.

Some use a calendar.

Some species will only flower at a particular time of year, and use day length as a reliable calendar.

Plants become hormonal.

Plant hormones (or phytohormones) play a critical role in stimulating flowering.

Some need a cold burst.

Some plants require a burst of cold weather before they will flower. This is called vernalisation.

Some learn their ABC's.

The 'ABC' and 'ABC(E)' models explain how floral development is controlled in plants.

Read more: Why potassium won't make your plants flower, discover flowers that turn back into leaves, understand the parts of a flower, or check out the references. There's also a convenient five-minute summary and information about this site.