Grafted Corals: What They Are, How They Form, and Why They’re Rare

In the reef aquarium hobby, the term grafted coral is commonly used for corals that show two or more distinctly different color regions within a single, continuous-looking colony. These pieces can display sharp splits, streaks, or zones of contrasting color and are prized for their unusual appearance.

Despite the name, this is not plant-style grafting and it’s not cross-breeding between coral species. What you’re usually seeing is tissue compatibility in action: fusion, long-term coexistence at a stable boundary, or regrowth that creates a “split-color” look over time.

What “Grafted” Usually Means Biologically

Most grafted-looking corals fall into one of these categories:

Tissue fusion (chimerism)
In rare cases, tissues from genetically different corals can fuse and persist together as a single functional unit (a chimera). This is documented in stony corals and is more likely during early life stages, though persistence into later stages can occur under certain conditions.

Same-genotype fusion (clone fusion)
Fragments from the same parent colony can re-contact and fuse back together as they heal and grow. This is widely used in aquaculture and restoration (especially with micro-fragment methods) and can create a seamless colony. It’s impressive, but it isn’t a true “graft” in the hobby sense because it’s still one genotype.

Stable growth boundaries
Two colonies can grow into contact and establish a long-term border instead of fully fusing. If neither side overwhelms the other, the result can look “grafted” even though the tissues remain biologically separate.

Why Most “Grafts” Fail: Allorecognition

Corals use a biological recognition system known as allorecognition to distinguish self/kin from non-self. When two corals touch, that compatibility check determines the outcome: fusion, tolerance, a stable boundary, or rejection. Compatibility is influenced by species, genetic relatedness, health, and system stability—so true long-term split-color colonies are uncommon and unpredictable.

How This Looks Across Popular Coral Groups

Euphyllia (Torch, Hammer, Frogspawn)
Euphyllia are often aggressive at contact and can sting nearby corals. Because of that, true, stable tissue fusion between different morphs is unlikely. When you see a “split-color” Euphyllia, it’s more often a persistent boundary effect or a visual outcome of growth and healing rather than a confirmed fusion event.

Faviids (Favia/Favites and related LPS)
Massive and encrusting LPS are a better fit for long-term boundary stability and are also heavily represented in restoration work where fragments (especially same-genotype fragments) are encouraged to rejoin and expand. In aquariums, balanced growth and low stress can help preserve crisp pattern transitions that collectors associate with “grafted” looks.

Cyphastrea
Cyphastrea’s encrusting nature makes it a strong candidate for clean, persistent borders and visually stable multi-zone colonies. While true fusion is still not guaranteed, Cyphastrea can create some of the most convincing “split-color” appearances when conditions stay consistent.

Other interesting candidates
Encrusting SPS like Montipora (and some Acropora contexts) can show compelling boundary behavior and, in certain life-stage scenarios, documented potential for chimerism in the scientific literature. These are also the types of corals where stable growth lines can look dramatic over time.

How to Tell a True Long-Term Split from a Temporary Look

A legitimate graft-like piece typically shows a stable boundary that persists through growth, with both regions continuing to expand over time. If the “split” disappears under more neutral lighting, fades after healing, or shifts dramatically with stress, it’s often a temporary effect rather than a stable long-term trait.

Why Collectors Care

Beyond the visual appeal, these corals highlight how complex coral biology really is—especially tissue recognition and compatibility. Similar concepts are also being explored in aquaculture and reef restoration, where placing fragments strategically can accelerate tissue coverage and create larger, healthier colonies.

In the hobby, “grafted” is a convenient label for a striking visual outcome. The most stable examples tend to come from mature systems where corals are healthy, undisturbed, and allowed to grow naturally over time.

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References

Forsman, Z. H., Page, C. A., Toonen, R. J., & Vaughan, D. (2015). Growing coral larger and faster: micro-colony fusion as a strategy for accelerating coral cover. PeerJ.

Page, C. A., Muller, E. M., & Vaughan, D. E. (2018). Microfragmenting for the successful restoration of slow growing massive corals. Ecological Engineering.

Puill-Stephan, E., Willis, B. L., van Herwerden, L., & van Oppen, M. J. H. (2011). High potential for formation and persistence of chimeras following aggregated larval settlement in the broadcast spawning coral Acropora millepora. Proceedings of the Royal Society B.

Puill-Stephan, E., et al. (2009). Chimerism in wild adult populations of the coral Acropora millepora. PLOS ONE.

Nozawa, Y., & Loya, Y. (2005). Rejection and fusion in juvenile scleractinian corals: role of allorecognition. Marine Ecology Progress Series.

Amar, K. O., Chadwick-Furman, N. E., & Rinkevich, B. (2008). Kin aggregations in reef corals: mixed allogeneic reactions and fusion. Marine Biology.

Jokiel, P. L., et al. (1994). Histocompatibility and regeneration in corals. Biological Bulletin.

Blanco-Pimentel, M., et al. (2024). Field-based grafting methods for coral restoration. Restoration Ecology.