Annual sunflowers spread through their seeds and, because of this, have many large seeds. But because of modern hybridization, there are now perennial sunflowers that have more seeds on their flower heads. … Perennial sunflowers grow in clumps with many stems coming out of the ground a tight clump.

Are sunflowers bad to grow?

You’ll find a few of the negatives of growing sunflowers here. Sunflowers can kill. Of all the issues with sunflowers, perhaps the most interesting and dire is their tendency to repress the growth of other plants. This is because sunflowers are allelopathic – they exude toxins that stop nearby plants from growing.

Do sunflowers come back every year?

Are sunflowers annuals or perennials? While most varieties of this bright beauty are annual sunflowers, meaning they will not come back the following growing season, they may self-germinate from dropped seeds if you leave the heads on the plants throughout the winter.