Review Allelopathic Effects of Moringa oleifera Lam. on Cultivated and Non-Cultivated Plants: Implications for Crop Productivity and Sustainable Agriculture Blair Moses Kamanga , Donita L. Cartmill , Craig McGill and Andrea Clavijo McCormick * Academic Editor: Rosilda Mara Mussury Received: 23 May 2025 Revised: 11 July 2025 Accepted: 14 July 2025 Published: 23 July 2025 Citation: Kamanga, B.M.; Cartmill, D.L.; McGill, C.; Clavijo McCormick, A. Allelopathic Effects of Moringa School of Agriculture and Environment, Massey University, Tennent Drive, Palmerston North 4410, New Zealand; b.m.kamanga@massey.ac.nz (B.M.K.); d.cartmill@massey.ac.nz (D.L.C.); c.r.mcgill@massey.ac.nz (C.M.) * Correspondence: a.c.mccormick@massey.ac.nz Abstract Moringa (Moringa oleifera Lam.) is widely recognised as a multipurpose crop suitable for human and animal consumption, medicinal, and industrial purposes, making it attractive for introduction into new ranges. Its extracts have been found to have beneficial impacts on various crop species and biological activity against multiple weeds, making their use in agriculture promising. However, concerns have also been raised about moringa’s potential to negatively impact the growth and development of other cultivated and non-cultivated plant species, especially in areas where it has been introduced outside its native range. To understand the positive and negative interactions between moringa and other plants, it is essential to investigate its allelopathic potential. Allelopathy is a biological activity by which one plant species produces and releases chemical compounds that influence the reproduction, growth, survival, or behaviour of other plants with either beneficial or detrimental effects on the receiver. Plants produce and release allelochemicals by leaching, volatilisation, or through root exudation. These biochemical compounds can affect critical biological processes such as seed germination, root and shoot elongation, photosynthesis, enzymatic activities, and hormonal balance in neighboring plants. Therefore, allelopathy is an important driver of plant composition and ecological interactions in an ecosystem. This review explores the positive and negative allelopathic effects of moringa extracts on other plant species, which may help to inform decisions regarding its introduction into new biogeographical regions and incorporation into existing farming systems, as well as the use of moringa plant extracts in agriculture. Keywords: allelochemicals; biostimulants; hormesis; inhibition; plant competition; productivity oleifera Lam. on Cultivated and Non-Cultivated Plants: Implications for Crop Productivity and Sustainable Agriculture. Agronomy 2025, 15, 1766. https://doi.org/10.3390/ agronomy15081766 Copyright: © 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/ licenses/by/4.0/). 1. Introduction Moringa oleifera Lam., “moringa”, is an introduced plant species in most parts of the world and currently cultivated in various tropical and sub-tropical countries due to its health and nutritional benefits [1]. Moringa can grow in and adapt to different climatic conditions, making it convenient for cultivation in various biogeographical regions, supporting its worldwide expansion and distribution. Nevertheless, there are concerns about the species becoming invasive when introduced in other areas outside its natural range [2–5]. Of particular interest is its allelopathic potential on native and other cultivated species, i.e., its ability to emit allelochemicals that can promote or inhibit the germination, growth, and establishment of other plants in proximity [ 6,7]. Agronomy 2025, 15, 1766 https://doi.org/10.3390/agronomy15081766