Avoid heat delay on garden mums

Temperature has a greater influence than day length on the flowering of garden mums. Univ. of Mass. floriculture specialist Tina Smith and Univ. of Conn. extension horticulture and greenhouse IPM specialist Leanne Pundt said the delay of flowering and failure of buds to develop properly (crown buds) are often caused by heat delay. Heat delay can occur when the night temperature exceeds 73°F. Garden mum cultivars vary in their sensitivity to heat delay.
Research at Kansas St. Univ. has shown that mums are more sensitive to heat delay when plants are exposed to high night temperatures during the first 2 weeks of short days when flower bud initiation is occurring. Exposure to high temperatures after 3 weeks of short days did not cause permanent damage and only resulted in delayed flowering.

Pictured: Garden mum cultivars vary in their sensitivity to heat delay, which occurs when night temperatures exceed 73°F during flower bud initiation.