Water is a crucial part of plant development, as too much or too little will cause problems, possibly killing the plant. Water is especially important in a greenhouse because it is completely under your control. Since different plants have different watering needs, you must maintain different watering cycle for the different varieties of plants in your greenhouse. A common way of watering plants in a greenhouse is to provide small amounts of water to the plants frequently.
Group plants that have similar watering needs together, so that those needing lots of moisture are together and plants that need to dry out between waterings are separated.
Secure the water wand to the hose and test it to make sure the water comes out like a gentle rain. You don't want the water to rush out too quickly, as splashing among plants makes them more susceptible to disease.
Water all the plants in your greenhouse with the wand when the soil in all the pots feels dry to the touch. Keep in mind that plants such as cacti will need water sparingly, so it is important to take the plant varieties into consideration.
Pass the wand over the plants quickly to water them. This will make the soil damp.
Return to water all the plants a couple minutes later, moving more slowly with the wand so the soil is saturated and the water is running from the drainage holes in each pot.
Check on your plants two days later. Touch the soil of each group to see which ones are still moist and which are completely dry. For the plants that are dry in the top one inch of the soil, establish a watering plan to water every couple days. For plants with moist soil, establish a watering plan to water these plants one to two times per week. Continue this cycle so all greenhouse plants have a regular watering system.