You need to water your sunflowers once per week with a deep soaking. That's how often water sunflowers need under normal conditions. Give them about 1 inch (2.5 cm) of water each time. This amount gets moisture down to the roots where your plants can use it. Light daily watering does more harm than good.
I've watched underwatered sunflowers droop with leaves hanging down like they've given up. But give them a good drink and they perk back up within hours. The first time I saw this happen I was amazed at how fast they bounced back. Now I know that wilting is just their way of asking for water.
Your sunflower watering schedule needs to change based on the weather and growth stage. Hot days above 90°F might mean watering twice a week instead of once. Cool rainy weeks might mean no watering at all. Pay attention to what the weather brings and adjust as needed. Your plants will tell you when they need more water.
UMN Extension research shows that the 20 days before and after flowering is the critical period for water. This is when sunflower water requirements peak. Your plants put massive energy into making that big flower head. Stress them with drought during this time and you'll get smaller blooms and fewer seeds.
The goal is to keep soil moist but not soggy. Sunflowers can handle some drought once they grow up. Their deep taproots reach moisture that other plants can't find. But that doesn't mean you can ignore them during dry spells. Water stress shows up fast in smaller flowers and stunted growth.
Check your soil moisture before watering sunflower plants. Stick your finger 2 inches into the ground near the base of the stem. If the soil feels dry at that depth, it's time to water. If it still feels moist, wait another day or two. This test stops you from both over and under watering.
I started using mulch around my sunflowers two years ago and it changed everything. A 3-inch layer of straw or wood chips keeps the soil cool and holds in moisture. I went from watering twice a week to once a week with better results. The mulch also keeps weeds down so your sunflowers don't have to compete for water.
Water in the morning when you can. This lets the leaves dry before nighttime and reduces disease risk. Wet leaves overnight can lead to fungal problems that weaken your plants. Point your hose or watering can at the base of the plant. Direct soil watering works better than spraying from above.
Container sunflowers need water more often than ground-planted ones. Pots dry out fast in summer heat. Check your containers every day and water when the top inch of soil feels dry. Your potted sunflowers might need water every other day during hot spells. Keep them happy and they'll reward you with beautiful blooms all summer long.
Read the full article: When to Plant Sunflowers: Full Guide
