Coffee, Caffeine & Your Plants: Friend or Foe?

Dr. Russell Sharp examines the effects of coffee and tea on plants, explaining how caffeine and other compounds (tannins, organic acids, sugars) can act as low-dose biostimulants but become inhibitory or toxic at higher doses. He covers root drench vs foliar applications, allelopathy, impacts on microbes and pests, and how repeated use can harm photosynthesis, nutrient uptake and root health.

Practical takeaways: occasional small amounts may help rooting, but regularly pouring leftover caffeinated drinks on houseplants can cause overwatering, chemical stress, microbial shifts and long-term damage—so avoid routine use and be cautious if trying coffee grounds as pest deterrents.

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Joanne Chory — Salk Institute (USA)

Mark Estelle — University of California San Diego (USA)

Steve Kay — University of Southern California (USA)

Krishna K. Niyogi — University of California Berkeley (USA)

Bob B. Buchanan — University of California Berkeley (USA)

Chris R. Somerville — University of California Berkeley (USA)

Julin N. Maloof — University of California Davis (USA)

Pamela A. Ronald — University of California Davis (USA)

Daniel J. Kliebenstein — University of California Davis (USA)

Justin O. Borevitz — University of California Berkeley (USA)

Natasha Raikhel — University of California Riverside (USA)

Julia Bailey-Serres — University of California Riverside (USA)

Siobhan Brady — University of California Davis (USA)

Michael F. Thomashow — Michigan State University (USA)

Sheng Yang He — Michigan State University (USA)

Brad Day — Michigan State University (USA)

Federica Brandizzi — Michigan State University (USA)

Jian-Kang Zhu — Purdue University (USA)

Scott Poethig — University of Pennsylvania (USA)

Zhenbiao Yang — University of California Riverside (USA)

Dominique Bergmann — Stanford University (USA)

Sharon R. Long — Stanford University (USA)

Wolf B. Frommer — Heinrich Heine University Düsseldorf (USA)

Martin Yanofsky — University of California San Diego (USA)

Joseph R. Ecker — Salk Institute (USA)

Detlef Weigel — Max Planck Institute for Biology Tübingen (USA)

Xuelin Wu — University of Maryland (USA)

Kent D. Chapman — University of North Texas (USA)

Donald R. Ort — University of Illinois Urbana-Champaign (USA)

Stephen P. Long — University of Illinois Urbana-Champaign (USA)

Elizabeth A. Ainsworth — USDA-ARS (USA)

Rebecca Bart — Donald Danforth Plant Science Center (USA)

Blake C. Meyers — Donald Danforth Plant Science Center (USA)

Jim Giovannoni — Cornell University (USA)

Tom Brutnell — Cornell University (USA)

Christine Foyer — University of Birmingham (UK)

Philip Poole — University of Oxford (UK)

Andrew Fleming — University of Sheffield (UK)

Alistair M. Hetherington — University of Bristol (UK)

Carolin Müller — University of Freiburg (UK)

Ian Graham — University of York (UK)

Philip Mullineaux — University of Essex (UK)

John P. Carr — University of Cambridge (UK)

Cathie Martin — John Innes Centre (UK)

Pernille Brodersen — University of Exeter (UK)

Jill Harrison — University of Bristol (UK)

Ottoline Leyser — University of Cambridge (UK)

Jim Haseloff — University of Cambridge (UK)

Dale Sanders — John Innes Centre (UK)

R. George Ratcliffe — University of Oxford (UK)

Charles Godfray — University of Oxford (UK)

Liam Dolan — University of Oxford (UK)

James U. U. (Jim) Whelan — University of Western Australia (Australia)

Barry J. Pogson — Australian National University (Australia)

Owen Atkin — Australian National University (Australia)

Susanne von Caemmerer — Australian National University (Australia)

Graham Farquhar — Australian National University (Australia)

Sally Aitken — University of British Columbia (Canada)

Carl J. Douglas — University of British Columbia (Canada)

Justin P. K. L. (Justin) Borevitz — Australian National University (Australia)

Marilyn Ball — Australian National University (Australia)

Rana Munns — CSIRO (Australia)

Mark Tester — King Abdullah University of Science and Technology (Australia)

James Whelan — La Trobe University (Australia)

Jeremy Timmis — University of Adelaide (Australia)

Peter Langridge — University of Adelaide (Australia)

Mathew A. Gilliham — University of Adelaide (Australia)

Ute Roessner — University of Melbourne (Australia)

Robert D. Furbank — CSIRO (Australia)

David J. Beerling — University of Sheffield (UK)

Howard Griffiths — University of Cambridge (UK)

Rowan F. Sage — University of Toronto (Canada)

Lewis Ziska — Columbia University (USA)

Lisa A. Donovan — University of Georgia (USA)

Robert A. Bressan — Purdue University (USA)

Erik H. Murchie — University of Nottingham (UK)

Tracy Lawson — University of Essex (UK)

Steven M. Driever — University of Illinois Urbana-Champaign (USA)

Yunde Zhao — University of California San Diego (USA)

Keiko Torii — University of Washington (USA)

Jen Sheen — Harvard Medical School (USA)

Xing Wang Deng — Yale University (USA)

Bonnie Bartel — Rice University (USA)

Jianhua Zhu — University of Maryland (USA)

José R. Dinneny — Stanford University (USA)

David W. Ehrhardt — Carnegie Institution for Science (USA)

Sabeeha S. Merchant — University of California Berkeley (USA)

Susan S. Golden — University of California San Diego (USA)

Shauna Somerville — University of California Berkeley (USA)

Dolf Weijers — Wageningen University (UK)

Anne Osbourn — John Innes Centre (UK)

Mike Roberts — Lancaster University (UK)

Robyn M. Gleadow — Monash University (Australia)

Brett Neilan — University of New South Wales (Australia)

Justin O’Sullivan — University of Auckland (New Zealand)

Richard Macknight — University of Otago (New Zealand)

Malcolm Hawkesford — Rothamsted Research (UK)

Marcel Salathé — University of British Columbia (Canada)

Stéphane Rolland — McGill University (Canada)

Owen K. Atkin — Australian National University (Australia)