What is an anthocyanin-free Sarracenia?
The genetics behind the green color
From historical discovery to Mendelian inheritance: everything you need to know about AF plants and their offspring
Anyone who starts collecting Sarracenia more seriously will sooner or later encounter the abbreviation AF. "Anthocyanin free", "antho free", or simply "AF": it pops up in grower catalogs, Facebook groups, and auction descriptions. But what exactly does it mean, how rare are these plants, and what happens when you cross an AF plant with a regular colored one? This article explains the genetics of the green Sarracenia from A to Z, including the winding scientific history that preceded it.
What are anthocyanins, and why are they normally present?
Anthocyanins are water-soluble pigments found in plants that are responsible for red, purple, and blue colors. In Sarracenia, they are responsible for the characteristic red veins, spots, and hues we see in the pitchers, hood, and flowers of most species. They are not merely decorative: anthocyanins are thought to serve as UV protection and may play a role in attracting insects as prey.
An anthocyanin-free plant, or AF plant, simply does not produce these pigments. The result is a completely green plant, from the pitcher to the flower. Not to be confused with 'lightly colored' or 'light green' plants: a true AF plant has no trace of red or purple, even under strong light or stress.
A long road to recognition: the history of discovery
The scientific documentation of green Sarracenia spans over a century and a half and reflects how slowly botanical research sometimes progresses without coordinated record-keeping.
American botanist Eaton is the first to describe a completely green form of S. purpurea. It is an observation without explanation; genetics were completely unknown at that time.
Botanist Wherry renames the completely green form of S. purpurea to S. purpurea var. heterophylla (later f. heterophylla). He already suspects it is an anthocyanin mutation, a remarkable conclusion for his time.
In Alabama, Frederick Case finds a completely green Sarracenia leucophylla, a spectacular find, as S. leucophylla is known for its pronounced red veins and white hood. The plant survives in cultivation.
Phil Sheridan and Bill Scholl are the first to take a structured approach: they cross green forms of several species with regular colored plants and observe the offspring ratios. The foundation for genetic evidence is laid.
Sheridan confirms that the AF trait is recessively inherited and color is dominant, through seedlings of a completely green S. rubra ssp. gulfensis. Whether it is actually an anthocyanin mutation is not yet certain at that time.
Sheridan & Mills confirm through controlled self-pollinations and interspecific crosses that it is a single recessive gene that causes the mutation in all Sarracenia species. They also localize the blockage in the biosynthesis pathway: between leucocyanidin and the pseudobase, a late step in anthocyanin production.
The genetics: recessive versus dominant
To understand the inheritance of AF, you don't have to be a biologist. The principle is the same as the classic Mendelian genetics you might remember from school.
A gene consists of two copies (alleles), one from each parent. In Sarracenia and anthocyanins:
The allele that enables anthocyanin production is dominant (A). One copy is enough to produce a colored plant. Both plants with genotype AA and Aa are visibly colored.
The AF allele (a) is recessive. Only if a plant has two copies of this allele (genotype aa) is it completely anthocyanin-free. One copy is enough to "activate" the color.
What do you expect from which cross?
Now for the theory: what does this mean in practice for a grower? The ratios are predictable, provided you know the genotypes of the parents. Below are the three most relevant scenarios.
Scenario 1: AF × AF (100% green)
If you cross two completely green plants (both genotype aa), then all offspring will be anthocyanin-free.
| a | a | |
|---|---|---|
| a | aa — green | aa — green |
| a | aa — green= | aa — green |
Scenario 2: AF × regular (colored, not a carrier)
If you cross an AF plant (aa) with a regular plant without the recessive gene (AA), then all offspring will be colored, but all will be carriers of the AF allele.
| A | A | |
|---|---|---|
| a | Aa — colored (carrier) | Aa — colored (carrier) |
| a | Aa — colored (carrier) | Aa — colored (carrier) |
Scenario 3: Carrier × carrier (3:1 ratio)
If you cross two carriers (Aa × Aa), you get the classic Mendelian ratio: 3 colored plants to 1 green. On average, one in four seedlings is AF.
| A | a | |
|---|---|---|
| A | Aa — colored | Aa — carrier |
| a | Aa — carrier | aa— green ✓ |
Summary of expected ratios
Based on the genotype of the parents, with large numbers of seedlings:
(aa × aa)
(aa × AA), but carriers
(Aa × Aa)
Are AF plants rarer or harder to grow?
In nature, completely green Sarracenia are rare but not non-existent. They are protected by their remote habitat locations more than by genetic factors. In cultivation, AF plants are becoming increasingly available thanks to targeted selection and thoughtful cross-breeding, although they remain far less common than colored forms.
In terms of cultivation, AF plants behave identically to their colored counterparts. They have the same requirements for water, soil, light, and dormancy. The absence of anthocyanins has no effect on the vitality, growth, or trapping capacity of the plant.
Same needs as colored species: full sun. AF plants do not turn red with more light, but they do grow more vigorously and compactly.
Exclusively rainwater, distilled or reverse osmosis water. Identical to all other Sarracenia.
Necessary. AF plants are just as winter hardy as their colored counterparts of the same species or hybrid.
Seedlings from AF parents can only be definitively assessed as AF when they are mature and show no red pigment under strong light.
One gene, all species
One of the most elegant findings from Sheridan's cross-breeding research is that it is the same recessive gene that causes the AF trait in all studied Sarracenia species. This was demonstrated through interspecific crosses: if you cross a green S. leucophylla with a green S. purpurea, and the offspring are also all green, then you know it is the same genetic mutation. If there had been two different genes, all offspring would have been carriers and thus colored.
Looking for an AF plant for your collection?
We cultivate a selection of anthocyanin-free Sarracenia and hybrids ourselves. Check our offer or contact us for availability.
View our Sarracenia rangeReferences
- Sheridan, P., & Scholl, B. (1996). Noteworthy Sarracenia collections II. Carniv. Plant Newslett., 25, 19–23.
- Sheridan, P. M., & Mills, R. R. (1998). Genetics of anthocyanin deficiency in Sarracenia L. HortScience, 33(6), 1042–1045.
- Sheridan, P. M., & Mills, R. R. (1998). Presence of proanthocyanidins in mutant green Sarracenia indicate blockage in late anthocyanin biosynthesis between leucocyanidin and pseudobase. Plant Science, 135(1), 11–16.
- Sheridan, P. M., & Griesbach, R. J. (2001). Anthocyanidins of Sarracenia L. flowers and leaves. HortScience, 36(2), 384.
📸 AF plant in your collection?
Do you have a beautiful anthocyanin-free Sarracenia in your collection, or have you grown seedlings from an AF cross yourself? Send your photos to killian@dupontflora.com, and who knows, your plant might be featured in a future article!
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