Even a native plant garden will occasionally benefit from supplemental watering, especially while new plants are establishing their roots, and during long, dry spells.
If you choose the right plant for the right place, you won’t have to water very often. Even during 2018’s intensely hot, and sometimes dry, summer, I only watered my pollinator garden a couple of times. Since I had added many new plants, I wanted to make sure their immature, shallow root systems had access to water.
Water when bees are not foraging
The easiest way to water to a garden is with a lawn sprinkler. It is usually recommended that you water in the morning so the sun will evaporate moisture off of leaves right away, and prevent fungal problems. If you water later in the day, water evaporates off of the ground before it soaks in, and you’re wasting water. If you water in the evening, moisture sits on the leaves overnight and may cause powdering mildew or other issues.
In a pollinator garden, you also need to consider the bees when you water. Do it when bees are not actively foraging — at dusk, at night, or at dawn. Bees can detect the drop in air pressure when it is going to rain. Bumblebees hide under flowers or leaves, and ground-nesting bees will return to their nests beforehand. Artificial watering has no early warning system. Watering during the day, while bees are out foraging, can destroy nest entrances, making it impossible for them to access their nests again.
For years, I have used soaker hoses to water dry areas of my gardens. I cut the ends off wire hangers to make pins for holding the hose in place. Since soaker hoses are on the ground, you avoid getting foliage wet and risking fungal problems. You can also weave a soaker hose around the most vulnerable plants, instead of watering everything whether it needs it or not. Since water seeps gradually and gently from a soaker hose, I doubt that it would destroy nest entrances.
Find your soaker hose before you dig. I have severed soaker hoses while shoveling.
Soaker hoses aren’t attractive. In a conventional garden, you would cover them with mulch to hold in moisture and to hide them. However, ground-nesting bees can’t dig through mulch, so mulch should be avoided in a pollinator garden. You can wait for vegetation to cover the hose, or remove the hose after the garden is a few years old and is established.
In my pollinator garden, I usually just hand-water with a watering can or hose to target only the plants that need it. I place a ring of mulch around new plants to prevent water from running off and to protect the roots.