Yellow oxalis (Oxalis corniculata) is frequently a serious pest in greenhouse rose production. When steam fumigation precedes planting, the oxalis seedlings and plants are killed. However, due to the three to five year interval between steam treatments, when the roses are producing, reinfestation occurs by seed from adjacent beds. The seed is ejected from the seed pod with sufficient force to carry for several feet into previously clean beds. The seeds cling to clothing and often to animals, enabling them to be spread throughout the greenhouse and even to be introduced from the outside.

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