Maine Wild Blueberry Phenology Guide – Detailed Summary
What is Phenology?
Phenology is the study of plant growth and development over time in response to environmental factors like temperature and sunlight. Monitoring the phenological stages of wild blueberries is essential for:
Effective pest management (e.g., timing pesticide applications).
Optimal fertilization schedules to promote growth.
Harvest planning to maximize yield and quality.
Assessing plant health and productivity.
Wild blueberries are genetically diverse, and their growth stages can vary between fields. However, over 70% of fields tend to follow a similar pattern, allowing farmers to use phenology as a guide.
Key Growth Stages of Wild Blueberries
Wild blueberries grow in a two-year cycle, alternating between a prune year (vegetative growth) and a crop year (flowering and fruiting). The guide divides plant development into two main sections:
Prune Stage (Vegetative Growth): Focuses on leaf and shoot development, preparing the plant for the following year’s fruiting cycle.
Crop Stage (Flowering & Fruiting): Involves bud development, bloom, and fruit maturation.
PRUNE STAGE (Vegetative Growth)
This stage occurs in the first year of the cycle when plants regenerate new shoots and leaves.
1. Leaf Emergence Stages
These stages mark the early vegetative development of the plant.
Early Green Tip: Small green tips (less than 2mm) emerge from overwintered buds.
Green Tip ½: Green tissue is visible on about 50% of stems, expanding to 2-5mm.
Shoot Expansion: Elongated shoots appear, growing in a whorled pattern along the stems.
2. Tip Die Back
The upper portions of last year’s stems dry out and wither.
This is a natural process as the plant reallocates resources toward new growth.
3. Bud Development
Bud development marks the preparation for flowering in the following season.
Bud Swell: Buds enlarge but remain enclosed.
Scale Separation: Bud scales begin to part, revealing the developing structures inside.
4. Leaf Drop & Bud Hardening
As temperatures drop, the plant enters dormancy.
Leaves turn red and eventually fall off.
Buds harden and turn brown as they prepare to overwinter.
CROP STAGE (Flowering & Fruiting)
This stage occurs in the second year of the cycle when plants produce flowers and develop fruit.
1. Leaf Emergence Stages (Same as Prune Year)
Leaves begin growing again as the plant prepares for fruit production.
2. Bud Stages
Flower buds undergo several stages before blooming.
Bud Swell (T1): Buds begin to enlarge but stay closed.
Early Bud Burst (T2): Outer scales separate slightly.
Bud Burst (T3): Flower clusters emerge from buds.
Tight Cluster (T4): Flowers remain tightly packed together.
3. Bloom (Flowering)
Bloom is a crucial stage for pollination and future fruit development.
Early Flower (T5): Some flower buds begin to open, revealing partially exposed petals.
Open Flowers: The majority of flowers are fully open, allowing for pollination by bees and other insects.
Petal Fall (Pin Head Stage): Petals drop off after pollination, leaving the small green pistil and stamens behind.
4. Fruit Development
Once pollinated, the flowers develop into fruit, passing through several growth stages.
Early Green Fruit: Small, firm, green berries begin to form.
Late Green Fruit: Berries enlarge but remain green.
Red Fruit: Some berries begin turning red as they ripen.
Blue Fruit: Fully ripe blueberries appear, ready for harvest.
Importance of These Growth Stages
Understanding these stages allows farmers to:
Apply fertilizers and pesticides at the right time.
Schedule bee pollination services to maximize fruit set.
Plan harvest timing based on fruit development.
Predict seasonal variations in crop yield.
Additional Notes
Leaf emergence often coincides with flower and bud stages.
The chart does not include dormant leaf and flower buds (T0, T1).
Some stages are adapted from studies on lowbush blueberries.
This guide helps wild blueberry farmers monitor plant health, optimize management practices, and improve yields by understanding the timing of each growth stage. Would you like any additional information on a specific section?