Growing giant sunflowers is a fascinating and rewarding gardening adventure. If you do it right, you can get huge plants with gigantic heads full of luscious seeds.

Here’s how to choose them, grow them, and harvest their seeds.

Giant Sunflowers

Choose the Right Variety

The variety certainly matters when it comes to growing giants. Look for a seed variety that uses words that mean “giant.” The name may actually be “giant” or it may use words like the mammoth, Kong, skyscraper, or titan.

Check the expected plant height and flower width on the package to be sure you’re getting seeds that can grow a plant as big as you want.

Site and Soil Preparation

Choose the site carefully. Your giant sunflowers will need full, direct sunlight. The more space you allow for each plant the better – preferably place them at least three feet apart. They need to have enough room for their root systems to spread out several feet. They also need a well-drained spot.

If you can, plant them next to a windbreak like a fence or a wall. They’ll need very rich, loamy soil, so add lots of compost before you get ready to plant.

One way to ensure rich soil is to dig a three-foot hole and add layers of compost, soil, and manure.

Plant Sunflowers

The Right Way to Sow and Thin

  • Wait until the danger of frost is past and the soil is at least 55 degrees F.
  • To sow your seeds, start by making your rows at least 30 inches apart.
  • Place the seeds into the rows about three feet apart.
  • Fertilize them lightly at planting time to help them develop strong root systems.
  • You can also place a screen or netting over the area to make sure birds and squirrels don’t steal your seeds.

Feeding and Care

  • Water your giant sunflowers around the root, about 4 inches from the plant.
  • After it’s established, water it deeply once a week. Feed it diluted fertilizer, but be sure not to over-fertilize.
  • If you want the biggest flower heads, use high phosphorus formula fertilizer as the head begins to form. And, don’t let the fertilizer get too close to the base of the plant.
  • Add bamboo stakes to keep them from falling over.
Sunflowers Care

Harvesting Giant Seed Heads

Soon, your giant sunflower will be ready to harvest. When the back of the flower head turns brown – about 30 to 45 days after it blooms – check the seeds to see if they’re ripe. Squeeze them.

If they’re hard and full, they’re ready to harvest. Then, cut off the head of the plant. Remove the seeds with a fork or your fingers. Or, you can cut the flower head before the seeds are ripe, hang it upside down, and then let the seeds ripen.

Once you’ve grown giant sunflowers once, it’s fun to challenge yourself or a neighbor to see if you can get larger and larger sunflowers. The more you practice the better you’ll do.

And, if you save the seeds of your best plants, you can work towards producing the tallest sunflowers yet.

What could be more interesting than that?

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