MSU Extension Blueberries

Growth Stages

Dormant or tight bud	Bud swell	Early green tip	Bud break or bud burst

Plant part: Flower bud. Description: No visible swelling of the fruit buds. Bud scales tightly closed. No visible signs of growth.	Plant part: Flower bud. Description: First sign of growth as plant growth begins in the spring. Visible swelling of the flower buds; outer bud scales begin to separate at the tip revealing paler interior bud scales. This bud stage can usually tolerate cold temperatures of 10 to 15⁰F (-12 to -9⁰C).	Plant part: Leaf bud. Description: Bud scales are separating at leaf bud tips. Green leaf tissue is emerging from the leaf bud tips. From 1/16 to 3/16 inch (2 to 5 mm) of green tissue is exposed. Leaves are tightly rolled.	Plant part: Flower bud. Description: Flower buds open and the individual flowers can be seen between the bud scales. Can tolerate cold temperatures of about 20⁰F (-7⁰C).
Late green tip	Tight cluster	Shoot expansion	Early pink bud

Plant part: Leaf bud. Description: Leaves are beginning to unfold. More green leaf tissue is visible, ¼ to ½ inch (6 – 13 mm). This stage generally occurs around flower bud burst.	Plant part: Flower. Description: Individual flowers are distinguishable in the flower cluster. This bud stage can tolerate 20 to 23⁰F (-7 to -5⁰C).	Plant part: Shoot expansion. Description: Multiple leaves have emerged from the vegetative buds and unfolded. Leaves are enlarging and shoot growth has begun.	Plant part: Flower. Description: Expanding flowers are readily visible and have separated. The pink corolla tubes (petals) are short and closed. This bud stage can tolerate 23 to 25⁰F (-5 to -4⁰C).
Late pink bud	Early bloom	Full bloom	Petal fall

Plant part: Flower. Description: Individual flowers fully developed. Expanded corollas are now white but still closed. This bud stage can tolerate 24 to 27⁰F (-4.4 to -2.8⁰C).	Plant part: Flower. Description: Some of the corollas are completely expanded and open. Many flowers are still closed. The bloom stages can tolerate 25 to 28⁰F (-4 to -2.2⁰C).	Plant part: Flower. Description: Most of the flowers on the bush have opened. The bloom stages can tolerate 28⁰ F (-2.2⁰C).	Plant part: Flower. Description: The corolla tubes are falling off the flowers, revealing small green fruit. This is the most vulnerable stage to freeze injury. Damage can occur at 32⁰F (0⁰C).
Early green fruit	Late green fruit	Shoot tip set; end of shoot growth	Fruit coloring

Plant part: Flower. Description: Small green berries are expanding. Fruit in the cluster varies from large to small pea-sized. Early fruit growth is by cell division.	Plant part: Fruit. Description: Growth of large fruit slows. Fruit becomes pale green. Exposed fruit may develop a red blush.	Plant part: Shoot. Description: Shoot tips die and shoot growth stops. No new small leaves can be seen emerging from the shoot tip. The dead shoot tip may be visible as a small dead leaf at the base of the last leaf on the shoot. In Michigan, there is typically one flush of growth in the spring, which ends before harvest. After harvest, some shoots will start growing again, for a second or third growth flush. These later growth flushes usually occur with moist soil conditions and moderate temperatures.	Plant part: Fruit. Description: Oldest, largest fruit in the cluster begin to change color from green to pink to blue. Fruit begins to soften. Cell division has stopped and fruit growth is by cell expansion.
10% Blue	25% Blue	75% Blue	Fruit bud set

Plant part: Fruit. Description: Single berries in the fruit clusters are ripe and ready to harvest. About ten percent of the fruits, on a bush or in the field, are ready to harvest. This stage is often used to begin the preharvest fungicides for fruit rots.	Plant part: Fruit. Description: 25 percent of the berries are ripe. 25% blue often coincides with first hand harvest of ripe berries.	Plant part: Fruit. Description: Blueberries are picked several times as the fruit ripens with 2 to 5 pickings. Often the first harvest is by hand and then later by machines that shake berries off the bush. 75% blue often coincides with the first of 2 machine harvests in the field.	Plant part: Shoot. Description: After harvest the blueberry bush stores reserves for next year’s growth. Shoot growth may begin again. Flower buds for next year’s crop form in September and October. These flower buds form first at the shoot tips. These large, clearly visible buds can be used to estimate next year’s crop potential.
Fall color

Plant part: Shoot. Description: At the end of the growing season, the leaves change color as nutrients are mobilized back into the shoots for growth next spring.

Horticulture