Are the sunflowers in your garden bed growing multiple heads? Should you leave them be or should you remove them straight away?
Sunflowers (Helianthus) can grow single flower heads or several flower heads depending on the species, variety, and cultivar. The best example, the wild sunflower, can grow as much as 20 flower heads per plant. Sunflowers can also grow multiple heads due to genetics or as an adaptation response to their external surroundings.
Having a lovely row of sunflowers for aesthetics, food, or industry is a worthwhile endeavor for any gardener looking to add a plant that combines form and function in one package.
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Sunflowers can grow multiple heads due to genetics or environmental adaptation. Specifically, wild sunflowers and its different varieties and cultivars grow more than one flower head per plant.
On the other hand, the domesticated sunflower varieties and cultivars such as the American Giant, the Skyscraper, the Russian Mammoth, among others, which only grow one (1) flower head.
Sometimes even single-headed sunflowers can grow multiple heads as an adaptation response to injury, environmental conditions, nutrients, and other factors.
There has been anecdotal evidence by gardeners that their single-headed variety or cultivar of sunflowers have suddenly become multi-headed. This is normal and nature working her way through adaptation and natural selection.
The first scenario is when sunflowers wilt and die during the first frost of the fall season. The dead sunflowers will drop their seed-filled heads and this will grow into a new sunflower. The next generation may have a chance to diverge from being single-headed to multi-headed.
This is most likely a result of genetic variation brought about by cross-pollination from the pollen of other sunflowers carried by wind or other pollen carriers.
The second scenario is when the sunflower suffers some sort of trauma or injury (i.e. pests, rabbits, or vermin attacking the sunflower), the sunflower, if it survives, would grow multiple heads even if it is from the single-headed variety.
The third scenario is that sunflowers will grow multiple heads due to favorable growing conditions. Sunflowers themselves only have modest fertility needs but they do respond well to a higher level of nitrogen in the soil. Hence, making sure a sunflower gets more nutrients without succumbing to nutrient burn will produce multiple heads.
We also have an in-depth guide on fertilizers so that you can better understand what you are feeding your plants. The below are good fertilizers.
All in all, these scenarios are natural occurrences in nature. The sunflower will appropriately respond to its external surroundings to better its chances of survival and reproduction.
We can break down sunflowers into two groups: 1) Single-headed and 2) Multi-headed sunflowers.
The most iconic sunflowers belong to the domesticated sunflower groups which are the ones most commonly produced. These sunflowers only have one large flower head.
These sunflowers are often those seen in popular media with their bright colors and distinct presence. There are many sunflowers varieties and cultivars which exhibit this trait, namely:
- American Giant
- Russian Mammoth
- Mongolian Giant
- Giant Sungold
- Pikes Peaks
- Giant Single
This is just to name a few. There are more species, varieties, and cultivars which are too many to enumerate but keep in mind that sunflowers come in all shapes and sizes despite having been analyzed to have come from a limited gene pool.
Multi-headed sunflowers grow multiple heads per plant and come from different species, varieties, and cultivars and are a result of natural genetic variation. The best example of a multi-headed sunflower is the wild sunflower which can produce as much as 20 heads per plant.
Multiple-headed sunflowers can produce significant yield due to having more seeds sources to harvest from. Examples of sunflowers that grow multiple heads are numerous
- Wild Sunflowers
- King Kong Sunflowers
- Maximilian Prairie
- Choco Sun
- Suntastic Yellow Sunflowers
There is a distinct mutation reported by some gardeners where two flowers grow on a single head. These mutations often look like conjoined twins wherein two flowers share the same receptacle.
The first variation comes with the head having two adjacent flowers facing different directions on a single receptacle. The second variation looks like a Venn diagram where the head has two flowers that share the same disc florets while still having separate sets of ray florets.
These mutations do not have any reported or documented hazardous origins such as harmful chemicals or radiation. Though rare, it seems to be a natural genetic mutation not out of the ordinary course of nature.
For gardeners who like this trait in their sunflowers for personal or academic purposes, it is recommended that the seeds be harvested and stored for the next growing season. This ensures this genetic trait will be perpetuated through successive plantings.
Breeding sunflowers is a very simple process which can be done with no tools or complicated devices. One only has to rub the pollen of one sunflower to the head of another sunflower.
Sunflowers have perfect flowers, this means that they have both male and female reproductive organs. They can self-pollinate or be cross-pollinated by other sunflowers.
The simplest method would be through hand pollination which involves nothing more than our fingers to complete. One may also use cotton buds, a feather, or a brush to do the procedure. It’s a completely safe, natural, and proven way to breed plants.
When finding a sunflower with desirable traits to the gardener, a gardener may simply rub their finger on the disc florets (the reproductive organ) on the flower to gather pollen. The gathered pollen should be applied to the flower head of the recipient sunflower.
This procedure is best done during the summer when the sunflower blooms. Thirty (30) days after pollination, the sunflower will produce seeds which should be secured. This will be the next generation of sunflowers which should be planted next season.
- Sunflowers can grow multiple heads due to genetics or as an adaptation response.
- Multiple flower heads are most commonly found in the non-domesticated sunflower species and varieties. The best example is the wild sunflower which can grow more than 20 flowers per plant.
- Sunflowers can be easily bred and hybridized because they have perfect flowers that have both male and female reproductive organs. Pollination can be done manually by hand.
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- “Breeding and Genetics” by Gerhardt Fick in Agronomy Monographs
- “Growing Sunflowers” by n/a in Teagasc – the Agriculture and Food Development Authority
- “Genetic, Genomics, and Breeding of Sunflower” by Hu et al in CRC Press
- “Inheritance of Branching in Sunflowers, Helianthus annuus L.” by E. A. Hockett and P. F. Knowles in Agronomy Department, University of California
- “Photos: Where the Sunflowers Shine” by Linda & Dr. Dick Buscher in LiveScience
- “Seed yield, head characteristics and oil content in sunflower varieties as influenced by seeds from single and multiple headed plants under humid tropical conditions” by Olowe et al in Annals of Applied Biology 163(3)
- “Sunflower” by n/a in Iowa State University
- “Sunflowers” by Kurt Nolte in College of Agriculture and Life Sciences – University of Arizona
- “Sunflower Hybrid Breeding: From Markers to Genomic Selection” by Aleksandra Dimitrijevic and Renate Horn in Front. Plant Sci., 17 January 2018
- “Wild Sunflower” by Godofredo Stuart in Philippine Medicinal Plants