Kumquats are a rather cold hardy variety of citrus, and because of their cold hardiness they are late blooming cultivars. One attribute of cold hardiness, is the ability not to readily lose dormancy and start growth with the first warm spell as do oranges, but to remain dormant until sufficient warm weather finally breaks the Kumquat's dormancy. Therefore Kumquat, and trifoliate oranges, bloom much later in the season than do other citrus. - Millet