Zoreah

1. In general, any action that initiates or promotes plant growth in any way is included in the prohibited Melacha called Zoreah (planting).
2. Planting of any amount is forbidden. The applications of this prohibition are planting, grafting, removal of obstacles to the plant, fertilizing, watering, spraying insecticide, putting seeds in water, and moving a plant in a bored pot.

Dropping seeds

1. One must be very careful not to drop or throw seeds, pits or cores of fruit or vegetables on the ground on Shabbat.
2. If one accidentally dropped a seed on Shabbat, if the seed is not muktzah (such as watermelon, apple, pear, or sunflower seeds, bird seeds) then it should be picked up right away (in order to violate Zoreah according to some opinions) and if the seed is muktzah (such as raw beans, raw peas, garden seeds, date pits, and date pits) it should not be picked up only after Shabbat.
3. Placing a seed on a well trodden path isn't a violation of Zoreah (because the seed won't sprout), however, this is inadvisable because one could misjudge the situation and many seeds are muktzeh. (for which seeds are muktzeh see last halacha).

Watering plants

1. It is forbidden to water a plant on Shabbat because of Zoreah.
2. Washing one’s hands over plants on Shabbat is forbidden because watering a plant helps it grow and is forbidden on Shabbat.
3. One should be careful not to spill any liquid or even to spit on plants on Shabbos.
4. Urinating on a plant isn't a violation of Zoreah (because the caustic fluid doesn't help the plant). See the halacha about urinating into dirt (Melachet Lash).

Putting flowers in a vase

1. One may not put tree branches in a vase with water on Shabbat; however, one may return them to water unless there are flowers on the branches. On Shabbat one may not add water to a vase with flowers or branches; however, on Yom Tov one may add water.