Tutorials/Flower farming

To grow flowers, you can apply bone meal on a grass block. The block must either have no block above it (obstructing sun/moonlight), or be lit with at least a light level of 8. Flowers and tall grass will spread over grass blocks up to 7 blocks radius around, i.e. 13×13 maximal area of growth. However, approximately 95% of growth occurs within a 9×9 area around the source grass block.

If the planting conditions are not met flowers will quickly pop out. This allows flowers to be used in the creation of light-sensitive mechanisms.

Flowers are useful for decoration, dyes, or breeding rabbits.

Another way to farm poppies is to kill iron golems using a sophisticated mob grinder, but that will only make sense if you want to have an infinite iron supply, it would be an extremely expensive way to farm poppies.

Poppies seem to be in "high demand" since they spawn much less than dandelion, so you may be able to sell them for high prices in Economy plugin servers. If you're having a hard time finding poppies, they tend to be most abundant in Extreme Hills biomes, but are also passably common in Taiga and Tundra.

As of 1.7.2, which adds many new flowers, different flowers can spawn depending on the biome you are in: Two-high flowers cannot be grown this way at all, instead they drop their copy when applying Bone Meal at a growing flower.

Flower farm design using water dispensers
On this design a redstone clock will trigger dispensers with water buckets, making water to harvest seed and flowers and taking them to you. As seen on the following video you stand at a central spot where you plant the bone meal, and water coming out from 4 dispensers take flowers and seeds to that central point.

Fully automatic design
This design adds an additional clock to power a dispenser full of bonemeal and a hopper to collect the drops, removing the need for manually placing and collecting the flowers.

Earthquake design
Another design, to make up for the absence of block updates caused by lighting, is to shift the ground with pistons.

Set up the design so that from the power source:

A dispenser dispenses bonemeal into the ground to produce flowers

A set of pistons pushes the ground one block in one direction

A set of pistons pushes the ground one block in the other direction, back to the original position.

Flower farm design using redstone lamp
(This design does not currently work as of 1.5.1).

On this design a redstone lamp will be triggered by a redstone clock, that will make the farm to go lit and fully dark on intervals. When the farmable grass blocks are lit you can farm them and when they are fully dark flowers and tall grass will pop out after a few seconds.

To speed up things there is a floor under the farm covered with redstone wire, that will force the game to update the farm blocks status when the wires get ON and OFF, if the redstone clock is set fast enough and the wire are connected to it flowers and tall grass will instantly pop out when planted.

On the following video also the redstone clock is set so the cycles are so fast the redstone lamp seems to be constantly ON, but is does actually get ON and OFF, so you can apply the bone meal anytime on the farm and everything will instantly pop out.