Zinc deficiency in plants: check the new leaves

By Joe Barrington, founder of Dr Forest

Quick answer. Zinc deficiency in plants shows on the newest growth first: small, narrow leaves bunched on short stems, pale yellow between the veins, older leaves still green. It's uncommon in UK gardens and turns up mainly on sandy, alkaline soil high in phosphate, and in fruit trees. Check the pH and rule out iron and manganese, then use a chelated trace-element feed such as Liquid Micronutrients (Micro-7) at the label rate, no higher.

I got interested in zinc after reading studies showing it really increased the essential oils in herbs, the terpenes that carry their smell and taste. After correcting a zinc shortage, I did notice a difference in flavour and aroma in herbs myself. So the link between zinc and herb flavour shows up when you correct a real shortage.

How to spot zinc deficiency in plants

Zinc doesn't move easily around the plant, so look at the tips. A plant short of zinc has small, narrow young leaves with pale yellow between the veins, bunched on short stems so the tip looks stunted, while the old leaves stay green. If the yellowing starts on the older leaves, it's probably not zinc: the usual causes are the same as for yellowing tomato leaves.

RB209, the UK fertiliser guide, says the few UK cases of zinc deficiency in plants have been on sandy soils with a high pH and high phosphate, and that top fruit is the most likely to show it [1]. In a garden, watch:

• sandy soil low in organic matter
• alkaline soil above about pH 7, where zinc gets locked up
• ground with years of heavy phosphate feeding, which gets in the way of zinc uptake
• apple, pear and plum trees
• cold, wet springs, when roots take up all the trace elements slowly

How to fix zinc deficiency

1. Check where the yellowing is. Pale new leaves of normal size usually mean iron or manganese, and yellowing that starts on old leaves is usually nitrogen or magnesium.
2. Test the pH. An alkaline reading on sandy or phosphate-rich ground is the best hint you'll get without a lab. My guide on how to test and change soil pH shows how to read it.
3. For a veg bed or a fruit tree, get a soil or leaf test. For one pot of basil, a measured feed costs less than the test.
4. Spray or drench with a chelated trace-element feed at the label rate, no higher. A spray reaches the new leaves fastest. Stop once new growth comes through green and full-sized.
5. Fix the soil over time. Add organic matter such as garden compost to sandy ground, cut back on high-phosphate feeds where a test shows phosphate is already high, and on limy soil feed the plant and leave the pH alone.

Zinc in the Dr Forest range

For zinc, use Liquid Micronutrients (Micro-7), a liquid trace element feed. It carries chelated zinc, iron, manganese and copper, plus boron, molybdenum and cobalt, with zinc the largest share at 0.75%. The garden rate is 7.5 ml in a 9-litre can as a spray or drench, no more than six times a year. You'll find it in the liquid fertilisers collection.

Each 7.5 ml dose carries about 56 mg of zinc. At 1 litre of mix per square metre a can covers 9 m², so each square metre gets about 6 mg. That's a small, measured top-up, which is what you want with a nutrient this easy to overdo.

What zinc does for plants

Zinc is one of the trace elements plants need in tiny amounts. That is why trace element feeds supply zinc for plants at very low rates, since too much is toxic. It is part of thousands of plant proteins, and it's toxic in excess [2]. It drives carbonic anhydrase, which helps feed carbon dioxide into photosynthesis, and plants need it to switch on the genes that help them cope with stress [3]. They need very little. RB209 says under 15 mg per kg of dry matter may mean a deficiency in susceptible crops [1]. Getting it in is the hard part on alkaline soil, which is why trace-element feeds use chelates, small molecules that hold the metal in solution. Some amino acids for plants do the same job.

Zinc, terpenes and the flavour of what you grow

The flavour link is clearest in herbs grown for their oil. Most of the trials come from India, Iran and the Mediterranean, where those herbs are a farm crop.

The route from zinc to terpenes

A herb's smell and taste come mostly from terpenes such as menthol, linalool and carvacrol, made from the sugars of photosynthesis and stored in oil glands on the leaf. Zinc plays its part through photosynthesis and the stress genes, so oil production should run best when the plant has enough. Overdoing it backfires: on a Cypriot oregano grown without soil, a high-dose zinc spray cut oil content, while a lower dose pushed the oil towards carvacrol [4].

Where the herb trials show real gains

• Menthol mint in India: 25 kg per hectare of zinc sulphate on top of the usual NPK raised oil yield by 55% on the CIMAP research farm (Kosi variety) and 37% across 42 farmers' fields. Almost all of it came from more leaf, as oil content rose only 3.5% [5].
• Moldavian balm under moderate salt stress made more oil with a zinc oxide nanoparticle spray plus a mycorrhizal inoculant, and the oil stayed rich in lemony geranyl acetate and geranial [6].
• Chamomile in Iran: an iron plus zinc spray raised oil yield by about 82% and oil content by about 25% over unsprayed plants [7].

Why tomatoes are different

Tomatoes give off over 400 volatiles, and the ones that matter most for smell come from carotenoids, fats and amino acids rather than terpenes [8] [9]. In an Italian greenhouse trial, zinc sprays raised fruit zinc by 66% without changing yield, and in one variety total sugars fell 13% and lycopene 8% [10]. In a two-season trial on processing tomatoes, zinc gave the best yields in two of three varieties but didn't improve acidity or lycopene [11].

Zinc still earns its place in the veg patch, because a plant badly short of it flowers and fruits poorly [3]. For tomatoes, think of zinc as part of growing a full crop. For basil, mint, sage and oregano, putting a shortage right is where a change in aroma has the best chance of showing.

Frequently asked questions

What are the signs of zinc deficiency in plants?

Small, narrow new leaves bunched on short stems, with pale yellow between the veins while older leaves stay green. Only a leaf or soil test is certain, because iron and manganese shortages look much the same on alkaline soils.

Is zinc deficiency common in UK gardens?

No, RB209 says it is rarely found in UK field crops. The exceptions are sandy, alkaline soils high in phosphate, and fruit trees.

Does zinc actually make plants taste better?

Only where the plant was short of it. Herb trials found more oil per hectare when zinc was added, mostly because the plants grew more leaf, and if your herbs aren't short of zinc, adding more won't make them smell stronger. Tomato aroma is built mostly from compounds other than terpenes, so expect less there.

How much zinc do plants actually need?

Very little. RB209 says under 15 mg of zinc per kg of dry matter may mean a deficiency in susceptible crops.

Can you use too much zinc?

Yes, and the gap between enough and too much is narrow, so stick to the label rate of any trace-element feed.

Sources

1. AHDB (2026). Nutrient Management Guide (RB209), Section 1: Principles of nutrient management and fertiliser use, Micronutrients, p. 30. https://ahdb.org.uk/knowledge-library/rb209-section-1-principles-of-nutrient-management-and-fertiliser-use
2. Broadley, M. R. et al. (2007). Zinc in plants. New Phytologist, 173(4): 677 to 702. https://doi.org/10.1111/j.1469-8137.2007.01996.x
3. Hafeez, B., Khanif, Y. M. and Saleem, M. (2013). Role of zinc in plant nutrition: a review. American Journal of Experimental Agriculture, 3(2): 374 to 391. https://doi.org/10.9734/AJEA/2013/2746
4. Chrysargyris, A. and Tzortzakis, N. (2025). Foliar application of iron and zinc affected growth, mineral content and essential oil profile in Origanum dubium Boiss. Journal of Soil Science and Plant Nutrition, 25(4): 10952 to 10966. https://doi.org/10.1007/s42729-025-02847-5
5. Lothe, N. B. et al. (2021). Maximizing yields and economics by supplementing additional nutrients for commercially grown menthol mint (Mentha arvensis L.) cultivars. Industrial Crops and Products, 160: 113110. https://doi.org/10.1016/j.indcrop.2020.113110
6. Ghaffari Yaichi, Z. et al. (2025). Zinc oxide nanoparticles foliar use and arbuscular mycorrhiza inoculation retrieved salinity tolerance in Dracocephalum moldavica L. by modulating growth responses and essential oil constituents. Scientific Reports, 15: 492. https://doi.org/10.1038/s41598-024-84198-2
7. Nasiri, Y. et al. (2010). Effects of foliar application of micronutrients (Fe and Zn) on flower yield and essential oil of chamomile (Matricaria chamomilla L.). Journal of Medicinal Plants Research, 4(17): 1733 to 1737. https://academicjournals.org/journal/JMPR/article-abstract/8AFCCB322605
8. Zhang, Z. et al. (2024). Volatilomics-based discovery of key volatiles affecting flavor quality in tomato. Foods, 13(6): 879. https://doi.org/10.3390/foods13060879
9. Klee, H. J. and Tieman, D. M. (2018). The genetics of fruit flavour preferences. Nature Reviews Genetics, 19(6): 347 to 356. https://doi.org/10.1038/s41576-018-0002-5
10. Cannata, C. et al. (2025). Effects of foliar applications of zinc on fruit biofortification and quality traits of greenhouse mini plum tomato cultivars. Journal of Agriculture and Food Research, 21: 101978. https://doi.org/10.1016/j.jafr.2025.101978
11. Nas, Y. and Duman, I. (2024). The effect of zinc fertilization on yield and quality of commercial processing tomato (Solanum lycopersicum L.) cultivars. Ege Üniversitesi Ziraat Fakültesi Dergisi, 61(3): 285 to 296. https://doi.org/10.20289/zfdergi.1460963