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Barret, R.; Daudon, M. An efficient synthesis of juglone. Synth. Commun. 1990, 20, 2907–2912. [ Google Scholar] [ CrossRef]The English walnut tree has smooth olive-colored bark when young that becomes deeply fissured and gray as it matures. English walnuts grow to around 65 ft. (20 m) with a crown of pinnate leaves just as wide. English walnut trees are the primary source of walnuts sold in stores today.

Duke, S.O.; Lydon, J. Natural Phytotoxins as Herbicides. In Pest Control with Enhanced Environmental Safety; Duke, S.O., Menn, J.J., Plimmer, J.R., Eds.; American Chemical Society: Washington, DC, USA, 1993; pp. 110–124. ISBN 780841213807. [ Google Scholar]Willis, R.J. The History of Allelopathy; Springer: Dordrecht, The Netherlands, 2007; ISBN 9781402040931. [ Google Scholar] The Manchurian walnut tree is native to East Asia and is one of the cold hardiest walnut trees. The fast-growing tall walnut trees are sometimes grown as ornamental trees because their nuts are small and difficult to extract. Manchurian walnuts are cold hardy in zones 2 – 8 and can withstand temperatures as low as -49°F (-45°C). Gopi, R.; Avasthe, R.K.; Kalita, H.; Yadav, A.; Das, S.K.; Dinisha, R.A.I. Eco-friendly management of tomato late blight using botanicals, bio-control agents, compost tea and copper fungicides. Indian J. Agric. Sci. 2020, 90, 35–39. [ Google Scholar] Babula, P.; Adam, V.; Havel, L.; Kizek, R. Noteworthy secondary metabolites naphthoquinones—Their occurrence, pharmacological properties and analysis. Curr. Pharm. Anal. 2009, 5, 47–68. [ Google Scholar] [ CrossRef] Durán, A.G.; Chinchilla, N.; Molinillo, J.M.G.; Macías, F.A. Influence of lipophilicity in O-acyl and O-alkyl derivatives of juglone and lawsone: A structure–activity relationship study in the search for natural herbicide models. Pest Manag. Sci. 2018, 74, 682–694. [ Google Scholar] [ CrossRef] [ PubMed]

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