Chamomile in cereal systems
Chamomile in cereal systems: between competition, ecological compatibility and agroecosystem functionality
Images of a cereal field crisscrossed by chamomile often evoke two opposing interpretations.
For conventional agriculture, chamomile represents a “weed” to be eliminated.
According to an agroecological approach, however, its presence can be interpreted as a possible ecological signal of biological compatibility, the functionality of the soil microbiome, and an increase in ecosystem complexity.
The truly interesting question, therefore, is not:
“Why does chamomile invade wheat?”
But rather:
“Why do wheat and chamomile so frequently manage to coexist in the same agroecosystem?”
Observing the scientific literature of recent years, the answer seems to lie in at least five ecological levels:
1. Pedoclimatic compatibility;
2. Microbiological compatibility;
3. Possible metabolic compatibility;
4. Ecological complementarity;
5. Ecosystem and trophic function of chamomile in cereals.
Chamomile as an Archaeophyte
Chamomile (Matricaria chamomilla L., syn. Chamomilla recutita) is an archaeophyte historically associated with European cereal systems.
From a phytosociological perspective, it frequently appears in seed communities belonging to the classes Stellarietea mediae and Papaveretea rhoeadis, typical of Mediterranean and European winter cereal systems (Mucina et al., 2016; Pignatti, 2017).
This represents real geobotanical evidence: chamomile is not simply an occasional species, but a relatively stable component of plant communities associated with cereals.
Therefore, we can state with reasonable certainty that wheat and chamomile occupy compatible ecological niches.
Phenological and Spatial Compatibility
Another reason why chamomile manages to persist in cereals is their strong phenological synchrony.
In fact, chamomile:
• germinates in autumn or late winter;
• It grows with dynamics similar to winter cereals;
• It tolerates light competition moderately;
• It has a relatively shallow root system;
• It completes its cycle concurrently with the maturation of the wheat.
From an ecological perspective, this means that chamomile has limited direct interference with wheat.
In fact, chamomile rarely displays the competitive aggression typical of highly disruptive spontaneous plants such as Lolium rigidum or Avena fatua.
However, it should be noted that in many cases it tends to occupy intermediate ecological niches in the cereal canopy (Toju et al., 2018).
This does not mean that there is a total absence of competition between the two species; it can be said that in unbalanced agroecological systems, high chamomile densities can reduce the availability of water, nutrients, and space for cultivation.
Multilevel Ecological Compatibility between Chamomile and Cereals
It should be emphasized that an agroecological perspective allows us to view the frequent coexistence between chamomile and winter cereals not exclusively as the result of a simple, random spatial overlap, but rather as a multilevel ecological compatibility, assessable through pedoclimatic, microbiological, metabolic, and trophic interactions between the two species.
From a geobotanical and phytosociological perspective, Matricaria chamomilla has historically been associated with European and Mediterranean cereal systems, frequently appearing in the seed communities typical of winter crops belonging to the Stellarietea mediae and Papaveretea rhoeadis classes (Mucina et al., 2016; Pignatti, 2017).
This association suggests environmental compatibility linked to shared conditions such as moderate soil disturbance, good light availability, autumn-winter cycles, and intermediate nitrogen fertility.
Significant ecological overlaps also emerge at the phenological level.
Chamomile exhibits germination and development dynamics compatible with those of wheat, showing generally moderate competition and often occupying intermediate ecological niches within the cereal canopy (Toju et al., 2018).
From this perspective, coexistence may depend not only on reduced direct interference, but also on the ability of the species involved to integrate within the same ecological mosaic.
In recent years, scientific attention has progressively shifted toward the role of the rhizosphere microbiome as a key element of agroecosystem functionality.
It is known that plants select specific microbial communities through the release of root exudates, flavonoids, sugars, and phenolic metabolites (Philippot et al., 2013; Venturi & Keel, 2016).
The available microbiological literature allows us to state with good certainty that chamomile and wheat can host recurrent and functionally relevant bacterial genera in the rhizosphere, frequently associated with promoting plant growth and soil ecological stability. Among the taxa most frequently reported in the scientific literature on agricultural systems and plant-microbe interactions are:
• Pseudomonas spp.;
• Bacillus spp.;
• Paenibacillus spp.;
• Streptomyces spp.;
• Rhizobium spp.;
• Azospirillum spp.
Many of these microorganisms are involved in key processes of agroecosystem functionality, including:
• promotion of root growth;
• phosphorus mobilization;
• siderophore synthesis;
• phytohormone production;
• increased tolerance to abiotic stress;
• competition against soil-borne phytopathogens (Kumar et al., 2020).
In the case of chamomile, Schmidt et al. (2014) experimentally demonstrated that bacterial inocula can significantly alter both the plant’s microbiome and secondary metabolism, highlighting a strong ecological plasticity of plant-microbe interactions.
Based on current knowledge, the presence of ecologically recurrent and functionally compatible bacterial genera in the rhizosphere of chamomile and cereals is scientifically supported.
However, the actual functional and dynamic sharing of these microbial communities in chamomile-wheat systems grown in the same agroecosystem remains to be experimentally validated through metabarcoding, metagenomics, or comparative crop isolation approaches conducted in the same pedological and phenological context.
Potentially relevant elements of convergence also emerge on a biochemical level. Chamomile and wheat share the production of flavonoids, phenolic acids, and other metabolites derived from the phenylpropanoid pathway, a central pathway in the regulation of plant-microbe interactions, stress responses, and ecological communication processes (Stringlis et al., 2019).
Although there is no direct experimental evidence of a true functional “metabolic compatibility” between these species, the presence of biochemical families common to both species makes the hypothesis of partial semiobiochemical continuity within the cereal system plausible.
Further evidence emerges from the literature on plant volatile organic compounds (VOCs). VOCs emitted by chamomile, including α-bisabolol, β-farnesene, and numerous sesquiterpenes, participate in processes of ecological communication, indirect defense, and modulation of multitrophic interactions (Dudareva et al., 2006; Heil & Karban, 2010).
In general, plant VOCs are known to influence the behavior of beneficial and phytophagous insects, contributing to the structuring of the semiochemical landscape of the agroecosystem (Kessler & Baldwin, 2001; Loreto et al., 2014).
In this context, the moderate presence of chamomile could contribute to increasing functional biodiversity and maintaining more complex food webs in cereal systems.
Finally, the plant diversification introduced by the presence of chamomile could promote increased microbiological heterogeneity and ecosystem resilience.
Increased plant complexity is frequently associated with more stable microbiomes, lower pathogen dominance, and greater resilience to environmental stress (Toju et al., 2018; van der Heijden & Hartmann, 2016).
From this perspective, chamomile could be interpreted not only as a companion species for cereals, but as a potential functional component of agroecosystem ecological networks.
Francesco Di Lorenzo
Agronomist
Essential Bibliography
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