Seeds can be harvested at any time, although often easier to harvest after the flower head is dried for several days. One of the largest-seeded varieties available to gardeners, seeds up to 1½” long. Plants can grow 12-14′ tall with gigantic yellow heads reaching 16-18″ across!” This Mongolian Giant Sunflower grew so big it need extra support. I mentioned that sunflowers do not like to dry out—or get waterlogged—and that means keeping the water nice and even, right through the growing season.

Sunflowers are pretty big compared to most flowers, but there’s one behemoth relative of the sunflowers we all know and love. Sunflower seeds should be planted outside in the ground as soon as the danger of a hard frost has passed to give them the longest possible growing season (and the tallest possible height. This is usually around March-May in most climates. Rouge Royale sunflower (formerly known as Moulin Rouge) is a multi-branch variety known for exotic color. Autumn Beauty’ sunflower grows to about seven feet tall. The blooms are slightly smaller (about six inches across), but the beautiful rusty hues make them the perfect plant for a fall garden. Even though it stays shorter than the rest of the varieties I mentioned above, I thought I’d add it to the list just in case you’re looking for a tall sunflower in a color other than yellow. ‘Autumn Beauty’ is a non-yellow sunflower variety that can grow up to seven feet tall. Bonus tip: Know your dwarf varieties Ring of Fire (1.2m): Heavily branching, bicoloured blooms, with petals dark red at their base surrounded by golden-yellow flames. Widely available. Blooming close to the sun…

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As the petals fall off, the center florets dry up and the seed kernels begin to swell in the disks, carefully climb a stepladder and cover your flower head with a mesh onion bag or loose burlap or paper bag. This keeps marauding birds from robbing your seeds so that the heads look perfect and complete when you are ready to show them off to friends or proudly display them on their long stalks at your local county fair. Cut the stalks at the base when the ripened seeds develop a hard shell. If you plan to eat your sunflower seeds or preserve them for your bird feeder, wait until the seeds are completely dry; then remove them by hand or by rubbing them over wire mesh into a basket. Store in tightly closed containers to keep rodents away. As per their delightful name, sunflowers not only look like the sun, they also love a sunny location. American Giant Sunflowers grow to reach about 16′ tall in good growing conditions. The flower head at the top can reach 12″ across. This variety takes about 80 days (2.6 months) to reach maturity after planting. 5. Titan sunflower Within the Genus Helianthus there are approximately 70 different species of sunflower, consisting of both annuals and perennials.

Each sunflower will need plenty of room to get as big as possible, so make sure you choose a spot that can accommodate them. They do best with around 1 to 2 feet between each flower.

Frequently asked question about growing sunflowers

When you’re planting a tall sunflower variety, you should take into account its expected maximum height and the expected size of the bloom. That’s because a lot of the tall varieties have been bred for height, but not necessarily for sturdiness. A crowded out sunflower reaching for the sun.

mammoth sunflowers will have improved growth with regular watering- these sunflowers were left to the elements Staking I’m holding a 10 foot 2×2 next to the stalk in the picture below. As you can see, the sunflower is more than ten feet tall. A plant that grows from seed to over ten feet tall in one year is very impressive. The 2×2 pictured is 10 feet tall. The Mongolian Giant Sunflower is taller. A closer view of the Mongolian Giant Sunflowers. The young buds of sunflowers move every day from east to west to face the sun, finally settling on facing east when the flowers open. This gives sunflower fields an astonishing regularity with all flowers pointing in the same eastwards direction. This growth movement of plants in response to the sun is called “heliotropism”, from the Greek helios for sun. I thought that planting the seeds in June, after our last frost date, would be much too late, so I started my sunflowers earlier indoors in cell trays.Mammoth sunflowers are included in these taller varieties, which can grow to impressive heights of 10 feet or more. The flowers are often very large as well, producing lots of seeds at the end of the season. I also found tips specifically for encouraging extraordinary growth saying to dig shallow trenches in circles around the plant—about 12 to 18-inches out, and add liquid fertilizer there, to reach more of the roots. I have not tried any of these things, but here’s what others say they use: compost, kelp, fish fertilizer, and a product like Osmocote. There are 70 different species of sunflowers around the world, with dozens, if not hundreds of cultivars, varieties, hybrids (i.e., types of sunflowers). They’re far from equal to each other in growing preferences, sizes, and colors, though, so you’ll want to study up on the selections before deciding to grow your own. We’ve categorized some of the most popular options to help you determine what you’re looking for. Read the minimal care instructions provided so you know what you’re getting yourself into with each. Tall, Giant, or Mammoth Sunflowers