Omnia SanaPlant Comparison
Peppermint vs Willow Bark
A side-by-side comparison of two medicinal plants — every documented constituent, action, use, safety note and cited source, assembled automatically from the Omnia Sana database.
At a glance
Peppermint and Willow Bark: they share 6 indicated uses (arthritis / joint pain, back pain, headache, …); 2 pharmacological actions in common.
Evidence face-off — shared uses
| Condition | Peppermint | Willow Bark | Verdict |
|---|---|---|---|
| Arthritis / joint pain | 5/10 | 7/10 | Stronger for Willow Bark |
| Back pain | 5/10 | 9/10 | Stronger for Willow Bark |
| Headache | 8/10 | 1/10 | Stronger for Peppermint |
| Inflammation (general) | 5/10 | 8/10 | Stronger for Willow Bark |
| Pain (general) | 5/10 | 9/10 | Stronger for Willow Bark |
| Skin irritation | 5/10 | 8/10 | Stronger for Willow Bark |
Evidence scores (1–10) are computed from the tier of each cited source. “Comparable” means the two scores are within one point. Follow a score to its detailed sources.
Key Constituents
Menthol is the dominant constituent of the leaf oil, responsible for the cooling sensation and much of the antispasmodic and analgesic activity.
Phenolic antioxidants of the leaf.
Metabolised in the body to salicylic acid - the 'natural aspirin' that gives the analgesic, anti-inflammatory and antipyretic effects.
Pharmacological Actions
Analgesic and anti-inflammatory for low back pain (moderate evidence; dose-dependent, around 240 mg salicin/day) - in an RCT, 240 mg salicin/day left 39% pain-free vs 6% on placebo within 4 weeks
Analgesic and anti-inflammatory for low back pain (moderate evidence; dose-dependent, around 240 mg salicin/day) - in an RCT, 240 mg salicin/day left 39% pain-free vs 6% on placebo within 4 weeks
Antipyretic (reduces fever)
Traditional & Indicated Uses
inferred from anti-inflammatory action
inferred from antimicrobial action
inferred from anti-inflammatory action
inferred from antispasmodic action
inferred from antispasmodic action
inferred from anti-inflammatory action
Relief of joint pain, osteoarthritis and rheumatic complaints
Analgesic and anti-inflammatory for low back pain (moderate evidence; dose-dependent, around 240 mg salicin/day) - in an RCT, 240 mg salicin/day left 39% pain-free vs 6% on placebo within 4 weeks
inferred from anti-inflammatory action
Analgesic and anti-inflammatory for low back pain (moderate evidence; dose-dependent, around 240 mg salicin/day) - in an RCT, 240 mg salicin/day left 39% pain-free vs 6% on placebo within 4 weeks; Relief of joint pain, osteoarthritis and rheumatic complaints
Safety, Cautions & Contraindications
Generally very safe. Essential oil should not be applied to the face or chest of infants or children — menthol can cause respiratory depression. Avoid enteric-coated capsules if taking antacids or acid-suppressing drugs. May worsen GERD by relaxing the lower oesophageal sphincter. Avoid in bile duct obstruction and gallstones.
Duke (2002) rates peppermint as +++ with clinical evidence (score 2) for antispasmodic activity, consistent with Commission E approval for IBS (irritable bowel syndrome) using enteric-coated peppermint oil capsules. Enteric-coated peppermint oil is one of the most clinically validated herbal treatments for IBS, reducing abdominal pain and spasm. Dose: 0.6 ml enteric-coated oil two to three times daily between meals (for IBS); 1.5–3 g dried leaf as tea three times daily for digestive complaints. Peppermint should not be applied near the face or nostrils of infants and small children (risk of laryngospasm from menthol). Contraindicated in cholelithiasis (gallstones) (Duke, 2002).
Because it works like aspirin, avoid willow bark if you are allergic to aspirin or salicylates, and do NOT give it to children or teenagers with a viral illness (risk of Reye's syndrome). Use caution in asthma (salicylate sensitivity).
Avoid with anticoagulant/antiplatelet medicines (bleeding risk) and in active peptic ulcer; avoid in pregnancy (especially the third trimester) and breastfeeding.
External Ids
Botanical Description
Perennial herb, 30-90 cm tall, a sterile natural hybrid (Mentha aquatica x M. spicata) that spreads by rhizomes and surface stolons rather than viable seed. Stems are square, often purple-tinged. Leaves are opposite, lance-shaped to ovate with a sharply toothed margin, and release a strong menthol scent when crushed. Small, pale purple flowers are borne in dense, interrupted terminal spikes.[2]
Large deciduous tree (Salicaceae), 10-25 m tall (occasionally taller), fast-growing with a broad crown. Leaves are narrow and lance-shaped, silvery-white and silky-hairy beneath, giving the tree a shimmering appearance in the wind. Tiny flowers are borne in catkins appearing with the leaves in spring; the species is dioecious. The fruit is a small capsule releasing cottony-tufted seeds.[12]
Habitat
A cultivated hybrid grown worldwide as a crop and garden herb, propagated vegetatively since it rarely sets viable seed; naturalised in damp ground - streambanks, ditches and waste places - in temperate regions.[2]
Native to Europe, western and central Asia and North Africa, growing on damp ground along riverbanks, floodplains and wet meadows; widely planted and naturalised elsewhere.[12]
Harvesting
Aerial parts are cut at or just before full flowering (mid- to late summer), when the essential-oil (menthol) content peaks, then dried quickly out of direct sun, or distilled fresh for essential oil.[3]
Bark is stripped from young branches (2-3-year-old growth is preferred, as salicin content is highest in younger bark) in spring, when the rising sap makes the bark peel most easily, then dried.[12]
Traditional Uses
Peppermint has one of the best-documented traditional uses of any herb - as a carminative and antispasmodic for indigestion, bloating and colic. Enteric-coated peppermint oil capsules are among the most clinically validated herbal treatments for irritable bowel syndrome, and topical or inhaled peppermint oil is traditionally and clinically used for tension-type headache and muscular aches.[1, 2, 4, 5]
Willow bark has one of the longest documented histories of any medicinal plant, used since antiquity (recorded by Hippocrates) as a remedy for pain and fever. Its salicin content, chemically related to aspirin, gives it official European herbal-monograph recognition for mild joint pain, headache and feverish colds, with modern clinical trials supporting benefit for low back pain.[11, 12]
Preparations
Dried leaf steeped in hot water, the classic digestive tea.
Standardised peppermint oil in enteric-coated capsules, the clinically studied form for irritable bowel syndrome, releasing the oil in the intestine rather than the stomach.
Diluted essential oil applied to the temples and neck for tension-type headache.
Dosage
Duke (2002) and Commission E guidance: about 0.6 mL enteric-coated oil two to three times daily between meals for IBS-type digestive complaints. Educational reference only, not a prescription.
Clinical trials for back pain have used around 240 mg salicin/day of standardised extract. Educational reference only, not a prescription; avoid if allergic to aspirin/salicylates, in children/teenagers with a viral illness (Reye's syndrome risk), or alongside anticoagulants.
References
Lookalikes Review
References & Sources
- McKay, D.L. and Blumberg, J.B (2006) 'A review of the bioactivity and potential health benefits of peppermint tea (Mentha piperita L.)', Phytotherapy Research, 20(8), pp. 619-633. doi:10.1002/ptr.1936 Meta-analysis / review
https://doi.org/10.1002/ptr.1936 - Mahendran, G. and Rahman, L.U (2020) 'Ethnomedicinal, phytochemical and pharmacological updates on Peppermint (Mentha x piperita L.)-A review', Phytotherapy Research, 34(9), pp. 2088-2139. doi:10.1002/ptr.6664 Meta-analysis / review
https://doi.org/10.1002/ptr.6664 - Zhao, H., Ren, S., Yang, H., Tang, S. and others (2022) 'Peppermint essential oil: its phytochemistry, biological activity, pharmacological effect and application', Biomedicine & Pharmacotherapy, 154, pp. 113559. doi:10.1016/j.biopha.2022.113559 Meta-analysis / review
https://doi.org/10.1016/j.biopha.2022.113559 - Keifer, D., Ulbricht, C., Abrams, T.R., Basch, E. and others (2007) 'Peppermint (Mentha piperita): an evidence-based systematic review by the Natural Standard Research Collaboration', Journal of Herbal Pharmacotherapy, 7(2), pp. 91-143. doi:10.1300/j157v07n02_07 Meta-analysis / review
https://doi.org/10.1300/j157v07n02_07 - Gobel, H., Heinze, A., Heinze-Kuhn, K., Gobel, A. and Gobel, C (2016) 'Peppermint oil in the acute treatment of tension-type headache', Schmerz, 30(3), pp. 295-310. doi:10.1007/s00482-016-0109-6 Meta-analysis / review
https://doi.org/10.1007/s00482-016-0109-6 - Nair, B (2001) 'Final report on the safety assessment of Mentha Piperita (Peppermint) Oil, Mentha Piperita (Peppermint) Leaf Extract, Mentha Piperita (Peppermint) Leaf, and Mentha Piperita (Peppermint) Leaf Water', International Journal of Toxicology, 20(Suppl 3), pp. 61-73. doi:10.1080/10915810152902592 Meta-analysis / review
https://doi.org/10.1080/10915810152902592 - Kobayashi, T., Sugaya, K., Onose, J. and Abe, N (2019) 'Peppermint (Mentha piperita) extract effectively inhibits cytochrome P450 3A4 (CYP3A4) mRNA induction in rifampicin-treated HepG2 cells', Bioscience, Biotechnology, and Biochemistry, 83(7), pp. 1181-1192. doi:10.1080/09168451.2019.1608802 Preclinical
https://doi.org/10.1080/09168451.2019.1608802 - Romero, M.C., Navarro, M.C., Martin-Sanchez, J. and Valero, A (2014) 'Peppermint (Mentha piperita) and albendazole against anisakiasis in an animal model', Tropical Medicine & International Health, 19(12), pp. 1430-1436. doi:10.1111/tmi.12399 Preclinical
https://doi.org/10.1111/tmi.12399 - Riachi, L.G. and De Maria, C.A.B (2015) 'Peppermint antioxidants revisited', Food Chemistry, 176, pp. 72-81. doi:10.1016/j.foodchem.2014.12.028 Meta-analysis / review
https://doi.org/10.1016/j.foodchem.2014.12.028 - Herro, E. and Jacob, S.E (2010) 'Mentha piperita (peppermint)', Dermatitis, 21(6), pp. 327-329. doi:10.2310/6620.2011.10080 Preclinical
https://doi.org/10.2310/6620.2011.10080 - Sun, Z. and Wang, H. and Wang, J. and Zhou, L. and Yang, P (2014) 'Chemical Composition and Anti-Inflammatory, Cytotoxic and Antioxidant Activities of Essential Oil from Leaves of Mentha piperita Grown in China', PLoS ONE. doi:10.1371/journal.pone.0114767 Preclinical
https://doi.org/10.1371/journal.pone.0114767 - Farco, J.A. and Grundmann, O (2012) 'Menthol - Pharmacology of an Important Naturally Medicinal “Cool”', Mini-Reviews in Medicinal Chemistry. doi:10.2174/138955713804484686 Preclinical
https://doi.org/10.2174/138955713804484686 - Geuenich, S. and Goffinet, C. and Venzke, S. and Nolkemper, S. and Baumann, I. and Plinkert, P.K. and Reichling, J. and Keppler, O.T (2008) 'Aqueous extracts from peppermint, sage and lemon balm leaves display potent anti-HIV-1 activity by increasing the virion density', Retrovirology. doi:10.1186/1742-4690-5-27 Preclinical
https://doi.org/10.1186/1742-4690-5-27 - Nolkemper, S. and Reichling, J. and Stintzing, F.C. and Carle, R. and Schnitzler, P (2006) 'Antiviral Effect of Aqueous Extracts from Species of the Lamiaceae Family against Herpes simplex Virus Type 1 and Type 2 in vitro', Planta Medica. doi:10.1055/s-2006-951719 Preclinical
https://doi.org/10.1055/s-2006-951719 - Mahady, G.B. and Pendland, S.L. and Stoia, A. and Hamill, F.A. and Fabricant, D.G. and Dietz, B.M. and Chadwick, L.R (2005) 'In Vitro susceptibility ofHelicobacter pylori to botanical extracts used traditionally for the treatment of gastrointestinal disorders', Phytotherapy Research. doi:10.1002/ptr.1776 Preclinical
https://doi.org/10.1002/ptr.1776 - Tullio, V.C. and Roana, J. and Scalas, D. and Mandras, N (2019) 'Evaluation of the Antifungal Activity of Mentha x piperita (Lamiaceae) of Pancalieri (Turin, Italy) Essential Oil and Its Synergistic Interaction with Azoles', Molecules. doi:10.3390/molecules24173148 Preclinical
https://doi.org/10.3390/molecules24173148 - Neves, A. and Rosa, S. and Gonçalves, J. and Rufino, A.T. and Judas, F. and Salgueiro, L. and Lopes, M.C. and Cavaleiro, C. and Mendes, A (2009) 'Screening of Five Essential Oils for Identification of Potential Inhibitors of IL-1-induced Nf-κB Activation and NO Production in Human Chondrocytes: Characterization of the Inhibitory Activity ofα-Pinene', Planta Medica. doi:10.1055/s-0029-1186085 Preclinical
https://doi.org/10.1055/s-0029-1186085 - Wu, Z. and Tan, B. and Liu, Y. and Dunn, J.L. and Guerola, P.M. and Tortajada, M. and Cao, Z. and Ji, P (2019) 'Chemical Composition and Antioxidant Properties of Essential Oils from Peppermint, Native Spearmint and Scotch Spearmint', Molecules. doi:10.3390/molecules24152825 Preclinical
https://doi.org/10.3390/molecules24152825 - Bojić, M. and Maleš, Ž. and Antolić, A. and Babić, I. and Tomičić, M (2019) 'Antithrombotic activity of flavonoids and polyphenols rich plant species', Acta Pharmaceutica. doi:10.2478/acph-2019-0050 Preclinical
https://doi.org/10.2478/acph-2019-0050 - Dorman, H.J.D. and Koşar, M. and Kahlos, K. and Holm, Y. and Hiltunen, R (2003) 'Antioxidant Properties and Composition of Aqueous Extracts from Mentha Species, Hybrids, Varieties, and Cultivars', Journal of Agricultural and Food Chemistry. doi:10.1021/jf034108k Preclinical
https://doi.org/10.1021/jf034108k - Benabdallah, A. and Boumendjel, M. and Aissi, O. and Rahmoune, C. and Boussaïd, M. and Messaoud, C (2018) 'Chemical composition, antioxidant activity and acetylcholinesterase inhibitory of wild Mentha species from northeastern Algeria', South African Journal of Botany. doi:10.1016/j.sajb.2018.03.002 Preclinical
https://doi.org/10.1016/j.sajb.2018.03.002 - Ayaz, M. and Sadiq, A. and Junaid, M. and Ullah, F. and Subhan, F. and Ahmed, J (2017) 'Neuroprotective and Anti-Aging Potentials of Essential Oils from Aromatic and Medicinal Plants', Frontiers in Aging Neuroscience. doi:10.3389/fnagi.2017.00168 Clinical study
https://doi.org/10.3389/fnagi.2017.00168 - Vladimir‐Knežević, S. and Blažeković, B. and Kindl, M. and Vladić, J. and Lower-Nedza, A.D. and Brantner, A (2014) 'Acetylcholinesterase Inhibitory, Antioxidant and Phytochemical Properties of Selected Medicinal Plants of the Lamiaceae Family', Molecules. doi:10.3390/molecules19010767 Preclinical
https://doi.org/10.3390/molecules19010767 - López, V. and Martin, S.D. and Gómez‐Serranillos, M.P. and Carretero, M. and Jäger, A.K. and Calvo, M.I (2009) 'Neuroprotective and neurochemical properties of mint extracts', Phytotherapy Research. doi:10.1002/ptr.3037 Preclinical
https://doi.org/10.1002/ptr.3037 - Orhan, İ.E. and Kartal, M. and Kan, Y. and Şener, B (2008) 'Activity of Essential Oils and Individual Components against Acetyland Butyrylcholinesterase', Zeitschrift für Naturforschung C. doi:10.1515/znc-2008-7-813 Preclinical
https://doi.org/10.1515/znc-2008-7-813 - Zeljkovıć, S.Ć. and Šišková, J. and Komzáková, K. and Diego, N.D. and Kaffková, K. and Tarkowski, P (2021) 'Phenolic Compounds and Biological Activity of Selected Mentha Species', Plants. doi:10.3390/plants10030550 Preclinical
https://doi.org/10.3390/plants10030550 - Desam, N.R. and Al-Rajab, A.J. and Sharma, M. and Mylabathula, M.M. and Gowkanapalli, R.R. and Albratty, M (2017) 'Chemical constituents, in vitro antibacterial and antifungal activity of Mentha×Piperita L. (peppermint) essential oils', Journal of King Saud University - Science. doi:10.1016/j.jksus.2017.07.013 Preclinical
https://doi.org/10.1016/j.jksus.2017.07.013 - Husain, F.M. and Ahmad, I. and Khan, M.S. and Ahmad, E. and Tahseen, Q. and Khan, M.S. and Al‐Shabib, N.A (2015) 'Sub-MICs of Mentha piperita essential oil and menthol inhibits AHL mediated quorum sensing and biofilm of Gram-negative bacteria', Frontiers in Microbiology. doi:10.3389/fmicb.2015.00420 Preclinical
https://doi.org/10.3389/fmicb.2015.00420 - Khayyal, M.T. and El‐Ghazaly, M.A. and Kenawy, S.A. and Seif-El-Nasr, M. and Mahran, L. and Kafafi, Y. and Okpanyi, S (2011) 'Antiulcerogenic Effect of Some Gastrointestinally Acting Plant Extracts and their Combination', Arzneimittelforschung. doi:10.1055/s-0031-1300078 Preclinical
https://doi.org/10.1055/s-0031-1300078 - Singh, R. and Shushni, M.A.M. and Belkheir, A.K (2011) 'Antibacterial and antioxidant activities of Mentha piperita L', Arabian Journal of Chemistry. doi:10.1016/j.arabjc.2011.01.019 Preclinical
https://doi.org/10.1016/j.arabjc.2011.01.019 - Dorman, H.J.D. and Koşar, M. and Başer, K.H.C. and Hiltunen, R (2009) 'Phenolic Profile and Antioxidant Evaluation of Mentha x Piperita L. (Peppermint) Extracts', Natural Product Communications. doi:10.1177/1934578x0900400419 Preclinical
https://doi.org/10.1177/1934578x0900400419 - İşcan, G. and Kırımer, N. and Kürkçüoğlu, M. and Başer, H.C. and Demi̇rci̇, F (2002) 'Antimicrobial Screening of Mentha piperita Essential Oils', Journal of Agricultural and Food Chemistry. doi:10.1021/jf011476k Preclinical
https://doi.org/10.1021/jf011476k - Akdogan, M. et al (2004) 'Investigation of biochemical and histopathological effects of Mentha piperita labiatae and Mentha spicata labiatae on kidney tissue in rats', 23(7), pp. 321--327. Preclinical
https://scholar.google.com/scholar?q=Investigation%20of%20biochemical%20and%20histopathological%20effects%20of%20Mentha%20piperita%20labiatae%20and%20Mentha%20spicata%20labiatae%20on%20kidney%20tissue%20in%20rats - Grigoleit, H.G. and Grigoleit, P (2005) 'Peppermint oil in irritable bowel syndrome', 12(8), pp. 601--606. Randomized trial
https://scholar.google.com/scholar?q=Peppermint%20oil%20in%20irritable%20bowel%20syndrome - Mas-Coma, S (2004) 'Fasciolosis in humans'. Traditional / reference
https://scholar.google.com/scholar?q=Fasciolosis%20in%20humans - Duke, J.A (2002) 'Handbook of Medicinal Herbs, Second Edition'. Traditional / reference
https://scholar.google.com/scholar?q=Handbook%20of%20Medicinal%20Herbs%2C%20Second%20Edition
- Shara, M. and Stohs, S.J (2015) 'Efficacy and Safety of White Willow Bark (Salix alba) Extracts', Phytotherapy Research, 29(8), pp. 1112-1116. doi:10.1002/ptr.5377 Meta-analysis / review
https://doi.org/10.1002/ptr.5377 - Maistro, E.L., Terrazzas, P.M., Perazzo, F.F., Gaivao, I.O.M. and others (2020) 'Salix alba (white willow) medicinal plant presents genotoxic effects in human cultured leukocytes', Journal of Toxicology and Environmental Health, Part A, 82(23-24), pp. 1223-1234. doi:10.1080/15287394.2019.1711476 Preclinical
https://doi.org/10.1080/15287394.2019.1711476 - Matyjaszczyk, E. and Schumann, R. (EU-FORA) (2018) 'Risk assessment of white willow (Salix alba) in food', EFSA Journal, 16(Suppl 1), pp. e16081. doi:10.2903/j.efsa.2018.e16081 Meta-analysis / review
https://doi.org/10.2903/j.efsa.2018.e16081 - Phillips, H.N., Sharpe, K.T., Endres, M.I. and Heins, B.J (2021) 'Effects of oral white willow bark (Salix alba) and intravenous flunixin meglumine on prostaglandin E2 in healthy dairy calves', JDS Communications, 3(1), pp. 49-54. doi:10.3168/jdsc.2021-0138 Preclinical
https://doi.org/10.3168/jdsc.2021-0138 - Kong, C.S., Kim, K.H., Choi, J.S., Kim, J.E. and others (2014) 'Salicin, an extract from white willow bark, inhibits angiogenesis by blocking the ROS-ERK pathways', Phytotherapy Research, 28(8), pp. 1246-1251. doi:10.1002/ptr.5126 Preclinical
https://doi.org/10.1002/ptr.5126 - Noleto-Dias, C., Ward, J.L., Bellisai, A., Lomax, C. and Beale, M.H (2018) 'Salicin-7-sulfate: A new salicinoid from willow and implications for herbal medicine', Fitoterapia, 127, pp. 166-172. doi:10.1016/j.fitote.2018.02.009 Preclinical
https://doi.org/10.1016/j.fitote.2018.02.009 - Wolfle, U., Haarhaus, B., Kersten, A., Fiebich, B. and others (2015) 'Salicin from Willow Bark can Modulate Neurite Outgrowth in Human Neuroblastoma SH-SY5Y Cells', Phytotherapy Research, 29(10), pp. 1494-1500. doi:10.1002/ptr.5400 Preclinical
https://doi.org/10.1002/ptr.5400 - Gagnier, J.J., van Tulder, M., Berman, B. and Bombardier, C (2006) 'Herbal medicine for low back pain (Cochrane review)', Cochrane Database of Systematic Reviews, (2), pp. CD004504. doi:10.1002/14651858.CD004504.pub3 Meta-analysis / review
https://doi.org/10.1002/14651858.CD004504.pub3 - Oltean, H., Robbins, C., van Tulder, M.W., Berman, B.M. and others (2014) 'Herbal medicine for low-back pain (Cochrane review update)', Cochrane Database of Systematic Reviews, 2014(12), pp. CD004504. doi:10.1002/14651858.CD004504.pub4 Meta-analysis / review
https://doi.org/10.1002/14651858.CD004504.pub4 - Amel Zabihi, N., Mahmoudabady, M., Soukhtanloo, M., Hayatdavoudi, P. and others (2018) 'Salix alba attenuated oxidative stress in the heart and kidney of hypercholesterolemic rabbits', Avicenna Journal of Phytomedicine, 8(1), pp. 63-72. Preclinical
https://scholar.google.com/scholar?q=Salix%20alba%20attenuated%20oxidative%20stress%20in%20the%20heart%20and%20kidney%20of%20hypercholesterolemic%20rabbits - Vlachojannis, J.E., Cameron, M. and Chrubasik, S (2009) 'A systematic review on the effectiveness of willow bark for musculoskeletal pain', Phytotherapy Research. doi:10.1002/ptr.2747 Meta-analysis / review
https://doi.org/10.1002/ptr.2747 - European Medicines Agency (HMPC) (n.d.) 'European Union herbal monograph on Salix [various species], cortex (Salicis cortex)'. Available at: https://www.ema.europa.eu/en/medicines/herbal/salicis-cortex Traditional / reference
https://www.ema.europa.eu/en/medicines/herbal/salicis-cortex - Chrubasik, S., Eisenberg, E., Balan, E., Weinberger, T., Luzzati, R. and Conradt, C (2000) 'Treatment of low back pain exacerbations with willow bark extract: a randomized double-blind study', The American Journal of Medicine, 109(1), pp. 9--14. doi:10.1016/S0002-9343(00)00442-3 Randomized trial
https://doi.org/10.1016/S0002-9343(00)00442-3
Generated automatically from the Omnia Sana plant database and its cited sources. For educational purposes only — not medical advice. Always consult a qualified practitioner before using medicinal plants.