Essential and Beneficial Elements: What Do Plants Actually Need?

Plants require 17 recognised essential elements to complete their life cycle. That does not mean these are the only elements they absorb, or that every other element is biologically irrelevant. Some additional elements can improve particular plant responses under defined conditions. Others are present without a demonstrated benefit, and some can be harmful.

The practical question is therefore not how many elements a fertilizer contains. It is whether a particular element is needed, available in a suitable form and concentration, and supported by evidence for the crop and conditions involved.

In cultivation discussions, I regularly see growers offer different nutritional explanations for the same photograph. That uncertainty is a reason to investigate plant condition and growing history, rather than assume that another element must be missing.

What the 17 essential elements include

The familiar list combines three elements obtained mainly from air and water with 14 mineral elements generally supplied through the root environment. The distinction matters: a product containing mineral nutrients does not supply all of the building materials or environmental conditions a plant needs.

Macronutrients and micronutrients are distinguished by the quantities required, not by whether they are important. A small requirement does not make an element optional, while a large supply of one nutrient cannot replace a different nutrient with another physiological role.

These categories provide a starting point for nutrition, not a universal fertilizer recipe. Requirements and appropriate tissue concentrations vary with species, cultivar, plant organ, developmental stage and growing conditions.

Essentiality requires more than detecting an element

The classical essentiality criteria ask whether a plant can complete its life cycle without an element, whether another element can replace its function, and whether the element has a direct role in plant metabolism. Establishing essentiality therefore requires more than finding an element in a leaf or observing a response after applying it.

Omission experiments are useful, but technically demanding. Seeds can contain reserves, water and chemicals can introduce traces, and removing an element from a nominal nutrient recipe does not necessarily remove it from the experimental system. Short experiments can also miss requirements that become apparent during reproduction.

Nickel provides a historical example. Brown, Welch and Cary (1987) investigated severely nickel-deficient barley, including the cultivar ‘Onda’. Their observations included impaired production of viable grain and alleviation of deficiency when nickel was supplied. The reproductive outcome was central to the essentiality argument; measuring leaf growth alone would have described only part of the response.

What a database of 52 elements does and does not show

Coker and colleagues (2026) compiled a global database covering concentrations of 52 elements in plant tissues, using 5,474 samples from 73 countries. The work demonstrates how much broader plant elemental composition is than a conventional essential-nutrient list.

It does not establish that every sampled plant contained all 52 elements, that all were measured in each sample, or that every detected element improved growth. Plant tissues can contain elements acquired from their surroundings without those elements fulfilling an essential nutritional function.

Three questions need to remain separate: was the element detected, does it have an established biological role, and does supplying more improve a relevant outcome? A compositional survey helps answer the first question. The others require different evidence.

Some benefits depend on the plant and its environment

An element can be beneficial without meeting the criteria for universal essentiality. Its effect may depend on species, exposure to a particular stress, background nutrition or interactions with other elements.

In a 2026 opinion paper, Gerendás and colleagues propose the term “conditionally beneficial elements” for elements that improve growth, development or reproduction in a given species under specified conditions. This is a proposed way to make the terminology more precise, not an experimental demonstration that every proposed beneficial element should be added to every crop.

The qualification matters in cultivation. An effect measured under nutrient deficiency or another challenging treatment does not automatically predict an improvement in an adequately supplied crop. A change in colour or metabolite concentration is also not, by itself, evidence of greater growth or total harvested production.

Silicon illustrates both potential and limits

Silicon is not part of the conventional list of 17 universally recognised essential elements. Its uptake and effects differ among plants, and it has been investigated for structural roles and responses to environmental and biological challenges.

Direct Cannabis research helps distinguish uptake from broader claims. Wise and colleagues tested a formulation containing silicate and phosphite and reported increased silicon in hemp leaves. However, the experiment evaluated a combined formulation, not silicon alone.

The reported increase in inflorescence yield had a p-value of 0.087, which does not meet a conventional 0.05 significance threshold. It should not be presented as a firmly established yield benefit, much less a universal recommendation for different cultivars or silicon products.

The study supports silicon availability from the tested treatment under its experimental conditions. It does not show that a plant without that supplement was deficient in an essential nutrient. The wider question is examined in Silicon in Plants: Food, Biostimulant or Structural Tool?

Iodine research raises a nutritional question without settling it

Kiferle and colleagues (2021) investigated iodine in hydroponically grown Arabidopsis thaliana, including growth and flowering responses, gene expression and incorporation of iodine into proteins. The phenotype experiments used the Columbia-0 background and compared a control solution with additions of potassium iodate.

In the reported experiments, iodate supply was associated with earlier flowering and changes in biomass and reproductive traits. The protein work also provided evidence that iodine can become part of plant proteins. These findings make iodine a serious subject for plant nutrition research, rather than merely an element detected incidentally in tissue.

They do not establish a universal iodine requirement for all crops. Nascimento and colleagues (2022) explicitly discuss this distinction and the need to demonstrate relevant effects across more plant species. They also emphasize toxicity at higher exposure.

Earlier flowering in Arabidopsis is not a direct prediction for flowering time or yield in Cannabis, pepper or another crop. Chemical form, concentration, exposure route and background conditions also affect interpretation. The crop-specific evidence and remaining questions deserve separate consideration in Do Plants Need Iodine Too?

A visible symptom does not identify a missing element

Yellowing, poor growth and damaged leaf margins can be associated with nutritional problems, but they can also arise from impaired water supply, unsuitable root-zone conditions, pests, disease or environmental injury. Even a genuine nutrient limitation does not necessarily mean that too little of the element was applied.

A nutrient can be present yet poorly available or insufficiently acquired. Interpretation depends on root condition, substrate chemistry, moisture, temperature and the interactions among nutrients. Increasing the fertilizer concentration without resolving the underlying limitation may leave uptake unchanged or add to salt stress.

The distinction between supply and acquisition is explained further in More Fertilizer, Less Uptake? The Roots Decide. It is a more useful starting point than treating each visible symptom as evidence that the nutrient list needs another entry.

Root-zone context matters more than a longer ingredient list

In a relatively inert substrate, such as rockwool, nutrition depends strongly on the irrigation solution and on how the root environment is managed. That calls for a complete, appropriate base programme and consistent delivery, not indiscriminate addition of trace elements.

Soils, composts, organic feeds and irrigation water can contribute nutrients and other elements, but their composition and availability vary. “Natural” does not guarantee an appropriate concentration, and the presence of a wide elemental range is not evidence of superior nutrition.

EC can help monitor dissolved ionic content, but it does not identify each element or establish that the nutrient balance is suitable. Water, substrate and tissue analyses answer different questions. Results need suitable sampling methods and interpretation for the crop and growth stage.

How to investigate whether something is actually missing

Begin with the crop’s condition and recent history, then check what is already supplied through fertilizer, water and substrate. Confirm actual irrigation delivery and examine root-zone moisture and other relevant measurements before introducing another input.

When an additional element is being considered, look for evidence that matches the crop, formulation, application route and growing conditions. A controlled trial should also distinguish a benefit from the effects of other ingredients in the same treatment.

For a home grower, consistent observations can help: dated photographs, new growth, pot-weight changes, water use and records of recent interventions. Where a nutrient question could materially change management, appropriate laboratory analysis may be more useful than another speculative supplement.

The broader inspection process is set out in Before You Add Anything, Learn to Read the Plant. A protective or growth response should be evaluated alongside possible costs and toxicity, rather than assumed from the word “beneficial”.

What this means for a feeding programme

The list of 17 essential elements remains a useful foundation. Research on additional elements expands our understanding of plant biology, but it does not make every detected element a missing fertilizer ingredient.

A defensible feeding decision combines an appropriate essential-nutrient supply, a functioning root environment and evidence for any additional treatment. Conditional benefits are worth investigating precisely because the conditions matter.

Product information

For the composition and application guidance of the products already discussed alongside these topics, see Ortho Origin and Iodine Insight. The studies discussed here do not establish the efficacy of either finished product. Product selection should follow the actual crop need and label instructions, not the assumption that additional elements are always beneficial.

References

Brown, P. H., Welch, R. M., & Cary, E. E. (1987). Nickel: A Micronutrient Essential for Higher Plants. Plant Physiology, 85(3), 801–803. https://doi.org/10.1104/pp.85.3.801

Coker, H. R., et al. (2026). The Elemental Composition of Land Plants: A Global Database and Meta-analysis. ACS Environmental Au, 6(5), 814–828. https://doi.org/10.1021/acsenvironau.6c00028

Gerendás, J., et al. (2026). Plant nutrient elements defined from the plant’s perspective. Plant and Soil, 526(2), 1049–1060. https://doi.org/10.1007/s11104-026-08946-1

Kiferle, C., Martinelli, M., Salzano, A. M., Gonzali, S., Beltrami, S., Salvadori, P. A., Hora, K., Holwerda, H. T., Scaloni, A., & Perata, P. (2021). Evidences for a Nutritional Role of Iodine in Plants. Frontiers in Plant Science, 12, 616868. https://doi.org/10.3389/fpls.2021.616868

Nascimento, V. L., Souza, B. C. O. Q., Lopes, G., & Guilherme, L. R. G. (2022). On the Role of Iodine in Plants: A Commentary on Benefits of This Element. Frontiers in Plant Science, 13, 836835. https://doi.org/10.3389/fpls.2022.836835

Wise, K., Simovich, T., Gill, H., & Selby-Pham, J. (2025; first published online 2024). Bioaccumulation of silicon and enhancement of cannabis inflorescence yield from fertiliser supplementation with the biostimulants silicate and phosphite. New Zealand Journal of Crop and Horticultural Science, 53(4), 1261–1273. https://doi.org/10.1080/01140671.2024.2339494

Montana State University Extension. Module 2: Plant Nutrition and Soil Fertility. https://landresources.montana.edu/soilfertility/html/modules/4449-2/index.html

Washington State University Extension. Chapter 4: Plant Mineral Nutrition and Fertilizers. The Pacific Northwest Gardener’s Handbook: Growing for the Future. https://extension.wsu.edu/pnw-gardeners-handbook/chapter-4-plant-mineral-nutrition-and-fertilizers/