How to Grow Ornamental Sunflowers
We frequently are asked how to grow sunflowers. Of course, after so many years it is pretty automatic for us. However, we realize that it can be challenging for novice gardeners who want to plant and enjoy sunflowers.
Fortunately, sunflower is pretty easy to grow. The sunflower genus, Helianthus, evolved right here in North America and many species of sunflower are found throughout the United States. So, sunflower is adapted to most growing conditions. Most importantly are daylight, adequate water, and fertile soils.
The sunflowers that we sell at SunflowerSelections.com are grown for all purposes. The hobby flower grower can try any of our bouquet or short stature sunflower varieties for use in the garden. We advise professional growers to test our sunflowers under their own conditions before committing to expensive mass plantings intended to generate income.
There is no one way to grow sunflower, but there are facts about sunflower that we like to emphasize.
1. Poor growing conditions will affect the sunflower plant. Lack of fertility, lack of adequate moisture, and competition with weeds will all reduce the vigor of the plant.
2. Likewise, day length and daytime and nighttime temperatures affect the growth of the sunflower plant. If you live in south Texas or Florida, your sunflowers may be shorter or taller, or earlier or later than if grown in Maine, for example. So, if you like to read about sunflower experiences on an internet bulletin board, be sure to weigh the information carefully.
3. The sunflower plant responds to space. If you want a larger diameter of flower, grow sunflower at a wide spacing from competing plants. The stems will be thicker, too. Grow sunflower plants closer together to get thinner stems and smaller flowers. Generally, plants grown closer together will be taller, too, than when spaced apart. However, remember that thinner stems are more delicate and high winds might snap off the plants. And of course, branching sunflowers will make more branches when you space them apart.
4. Transplanting - Many growers like to start their plants early and transplant them to their gardens. It is very important to realize that sunflower plants make a central tap root that likes to grow straight down into the soil. Maximum growth is achieved when this process occurs without disturbance. Plant scientists know that growing conditions such as stress and day length as early as from three weeks after emergence can trigger the plants to flower earlier. So, if you like to germinate your plants in trays under lights be aware that transplanted plants will ALMOST ALWAYS be shorter in height when they flower than if they were planted directly into soil. And if your want to grow the REALLY GIANT plants like KONG and AMERICAN GIANT HYBRIDS, you will get the best growth by planting them directly into the soil in the garden so that their central tap roots are never disturbed.
Our dwarf sunflowers like Junior, Firecracker, Baby Bear, and Munchkin grow well in six pack trays and easily transplant. Just 5 weeks from sowing you will have a firm root ball that easily separates from the tray. Check out the product page photos for Junior to see transplant trays ready in five weeks!
5. Soil Fertility - Over the years we have heard comments from growers that when they first grew sunflowers, the plants were big and lush, and now after 10 years they are smaller, and not as vigorous. They wonder if we have changed the genetic composition of the variety. The reality is that the fertility of the soil has probably changed. Remember when you cut sunflowers for flowers, you are taking a lot of biomass from the field - the leaves, the stems, and the heads. You need to put a lot of organic material and fertilizer (natural or synthetic) back into the soil to compensate for what you take out. Sunflowers are deep feeders. Over time they will literally wear out the soil if you do not practice good stewardship of your land.
We found a great link that demonstrates nutrient deficiencies in sunflower. Bear in mind that many symptoms of soil deficiencies appear similar. And some even appear similar to symptoms of sunflower diseases. Use this link as a first stop, then see your local soil extension specialist.
Sunflower Nutrient Toxicities and Deficiencies:
There are number of publications on the internet where you can gain more knowledge about growing ornamental sunflower.
Weed Control Link:
Disease and Insect Problems
Being native to North America, the many species of sunflower have co-evolved with numerous insects and plant pathogens. Moreover, sunflower's introduction as a crop plant into Europe, Asia, South America, and Australia during the last century has resulted in even more pests being discovered.
Fortunately for sunflower growers, plant breeders have done a good job in the last 70 years by selecting strains that can withstand most sunflower pests. Wild species that have adapted to pressure from the onslaught of sunflower insects and pathogens have contributed greatly to the development of modern crop and ornamental sunflower varieties that also tolerate most challenges from Mother Nature.
Sunflowers that are grown for cut flowers escape at least half of the serious fungal diseases that can plague sunflower when the heads are left to mature for seed harvest.
Most common diseases that attack sunflower in the pre-flower stages are:
Nice links with photos of symptoms of diseases and pests sunflower pests are:
|Downy Mildew ||Enters seedlings during germination. Stunts the plants. Manifests itself by white spores on the under leaf of the plant usually concentrated near the veins and stems. |
|Verticillium Wilt || Usually seen after flowering but can occur before when conditions are hot. Easiest symptom are drying of half leaves following a leaf vein. Usually on one side of plant while other side of plant can appear healthy. |
|Red Rust ||Starts on lower leaves and spreads up the plant. Looks like black soot was sprinkled on the leaves. Easily seen on the underside of the leaf. |
|Sclerotinia Wilt ||Can cause wilt of the plants usually after they are 40 days old. Roots have black hard fungal bodies near the surface of the stem. Can also be found in the stem. |
|Powdery Mildew ||Common where there is high humidity and warm temperatures. Very common in dense plantings of ornamental sunflowers. |
|Alternaria spp. || Causes angular leaf spots on leaves and sometimes stems. |