Nectar is used to turn Pikmin from leaf or bud stages to the flower stage. There are numerous places where nectar is found; Egg, Ujadani, Iridescent Flint Beetles, Iridescent Glint Beetles, Nectar Weed patches, piles of rocky Rubble, Mitites, Honeywisps, Nectarous Dandelflies, Yellow Spectralids, and yellow Unmarked Spectralids can all drop globs of nectar.
Nectar makes an appearance in Nintendo Land's attraction Pikmin Adventure. Nectar is a common item that can be found inside "?" blocks, and are leftovers from destroyed enemies. When a player collects 3, they will level up. It takes level 5 to get a bud, and level 10 to get a flower. As a Pikmin, you will drop a few drops of nectar when shaken off of an enemy. When your player is hit, they will drop a few drops of nectar, as well.
If you aren't doing very well on a specific stage, the game will eventually spawn a rainbow "!" block near your starting point. Once this block is broken, you will automatically receive level 50 in nectar.
"Nectar is a condensed, highly nutritional food source that has been scientifically proven to encourage a Pikmin's growth. Also, it looks delicious."
Nectar behaves differently in Pikmin 3. Nectar consumption is limited to 10 Pikmin per droplet. However, individual Pikmin will drink the droplet bit by bit, making it shrink in size, rather than a single Pikmin drinking all of the Nectar at once.
Pikmin 3 Prima Guide
"This golden liquid causes immature Pikmin to instantly blossom. Pikmin move much faster once they've matured, so try to make use of any nectar you find.
In Pikmin, the Pikmin can only drink nectar if the blob is at "full size".
There is glitch that occurs if a drop of nectar, such as one from a petrified enemy, falls on top of a pile of sticks used to build a bridge. If the sticks are removed from under the drop by building the bridge, the drop remains suspended in the air. Pikmin can be made to drink the nectar by throwing them at it, and they will fall back to the ground once the nectar is all used up.
Another glitch can occur if Olimar walks into a drop of nectar and starts throwing Pikmin. Sometimes the pikmin will hit the surface of the nectar from underneath and bounce right back in front of Olimar. Olimar then cannot collect the pikmin.
The best way to get a lot of Pikmin flowered is to use a few flower Pikmin to pull the grass/break the rocks to get the nectar, as flower Pikmin won't drink nectar. This will save the problem of a single Pikmin drinking an entire blob because it lands on top of it. Then, swarm as many leaf and/or bud Pikmin as you can to the nectar. This strategy does not apply to Pikmin 3 because nectar has been limited to ten individual uses only.
In Pikmin, there are only 3 ways to get nectar- Honeywisps, Nectar Weed and Stones. In Pikmin 2, there are 6 ways to get nectar- Unmarked Spectralids, Ujadani, Mitites, Honeywisps, Nectar Eggs and the usage of Ultra-bitter Spray. In Pikmin 3, Nectar Eggs, Nectarous Dandelflys & Yellow Spectralids are the only source of nectar in the game.