The bee balm water needs are moderate but steady. Your plant wants soil that stays evenly moist. Aim for about 1 inch (2.5 centimeters) of water per week from rain or your hose combined. Bee balm doesn't need a swamp, but it hates drying out on you.
I watched this play out during a brutal dry spell two summers ago. We went three weeks without good rain, and I didn't water my bee balm in time. The leaves curled inward at the edges first. By week two, my plants wilted every afternoon and bounced back each morning. By week three, white mildew covered the lower foliage. The drought had weakened my plants enough for the fungus to move right in. That experience taught me to never let my bee balm go thirsty again.
My neighbor learned the same lesson the hard way in her garden too. She went on vacation for two weeks during a hot July stretch. Her bee balm looked awful when she got home. Half the foliage had mildew and the flowers had wilted off the stems. You can prevent this with a soaker hose on a timer if you travel during the hot months.
The link between dry soil and disease is clear. Illinois Extension found that drought makes your bee balm more prone to powdery mildew. The stress weakens your plant's defenses against the fungal spores. Keeping the soil moist doesn't just make things look better. It keeps your plant's immune system strong enough to fight off the mildew.
Good news for you: bee balm handles wet feet better than most flowers. NC State Extension lists it as tolerant of wet soil. That makes it a great pick for your rain garden or low spots where water collects after storms. You're far more likely to hurt your plant by underwatering than by giving it too much. That wet-soil tolerance gives you room to be generous with your hose.
Setting up a bee balm watering schedule depends on your soil. Sandy soil drains fast and may need water twice per week during hot weather. Clay holds moisture longer and might only need water once a week from you. Stick your finger 2 inches (5 centimeters) into the soil near your plant's base. If it feels dry at that depth, water now. If it still feels damp, check again the next day.
The bee balm moisture requirements shift with the seasons too. Spring growth doesn't demand much since cool air slows the drying process. Summer heat is when you need to watch. Plants in full sun during 90°F (32°C) days burn through your soil moisture fast. Container-grown bee balm needs water from you even more often since pot soil dries out quicker.
Water at the base of your plant in the morning. Wet leaves create the ideal setup for mildew spores. A soaker hose or drip line along your bed puts water right at the roots where it belongs. Add 2 to 3 inches (5 to 7.5 centimeters) of mulch around your plants to lock in moisture. This pair of ground-level watering and mulch makes the biggest difference in keeping your bee balm healthy all season long.
Read the full article: Bee Balm Plant: How to Grow and Care
