Is it too late to thin out sunflowers after they begin to put on heads? I planted an acre of them but came up really small.
Certified GKH Gardening Expert
Yes, you can thin your plants as young seedlings, then again at 12 inches and a last thinning can be done when the plants are 2 feet tall.
This will help you develop the largest heads for seeds.
You can cut the plant down if pulling will disturb the other plants roots.