The present invention provides a plant growth control method, which utilizes a light source with photosynthetic photon flux density for R:G:B being 1.4-2.2:1.3-2.1:1 to provide the required lighting condition for the plant during the seedling period. Thus, the present invention may effectively inhibit the occurrence of over growth phenomenon during the seedling period and help the plant growing as healthy seedlings for enhancing plant productivity and quality by relatively more aggressive and reliable means.本發明之植物生長控制方法，主要係以光合作用光子通量密度R：G：B為1.4~2.2：1.3~2.1：1的光源提供植物在育苗期所需之光照條件。俾可有效抑制植物於育苗期發生徒長的現象，以及有助於植物成為健康的種苗，以相對更為積極、可靠之手段提升植物之產能及品質。
