The average number of days and heat units required for various growth stages of cotton
Growth Stage
Days
Heat Units – DD60s (15.6 C)
Description
Planting to Emergence
4 to 9
50 to 60
Emergence: Hypocotyl with cotyledons breaking through soil surface (crook stage)
Emergence to First Square
27 to 38
425 to 475
First true leaf unfolded (counted from the cotyledon node = node 0). A square is a flower bud. The first square occurs on the first fruiting branch at approximately 5-7th nodal position above the cotyledons
Square to Flower
20 to 25
300 to 350
The first square will develop into the first flower within 15-20 days (~8-10 weeks after emergence).
Planting to First Flower
60 to 70
Beginning of flowering: (early bloom: 5-6 blooms per 25 ft (7.5 m) of row
Flower to Open Boll
45 to 65
850 to 950
Full flowering (mid bloom): 11 or more blooms per 25 ft (7.5 m) of row- 10% boll open
Planting to Harvest Ready
130 to 160
2200 to 2600
Harvest Ready: 60% leaves fall off; Above ground parts of plant dead; plant dormant; crop matured, Harvest seed cotton
BBCH developmental stages of cotton
BBCH
BBCH DESCRIPTION
09
10
Cotyledons completely unfolded
11
First true leaf unfolded (counted from the cotyledon node = node 0)
12
2nd true leaf unfolded (counted from the cotyledon node = node 0)
13
3rd true leaf unfolded (counted from the cotyledon node = node 0)
19
9 or more true leaf unfolded, no side shoots visible1
21
First vegetative side shoot (2nd order) visible (counted from the cotyledon node = node 0)
22
2nd vegetative side shoot (2nd order) visible (counted from the cotyledon node = node 0)
29
9 or more vegetative side shoots (2nd order) visible (counted from the cotyledon node = node 0)
31
Beginning of crop cover: 10% of plants meet between rows
32
20% of plants meet between rows
33
30% of plants meet between rows
39
Canopy closure: 90% of plants meet between rows
51
First floral buds detectable (pin-head square)2
52
First floral buds visible (match-head square)2
55
Floral buds distinctly enlarged
59
Petals visible: floral buds still closed
60
First flowers opened (sporadically within the population)
61
Beginning of flowering (early bloom: 5-6 blooms per 25 ft (7.5 m) of row
65
Full flowering (mid bloom): 11 or more blooms per 25 ft (7.5 m) of row
67
Flowering finishing (late bloom): majority of flowers faded
69
End of flowering
71
10% of bolls have attained their final size
72
20% of bolls have attained their final size
79
90% of bolls have attained their final size
80
First open bolls on the first fruiting branches
81
Beginning of boll opening; about 10% of bolls open (nodes above white flower NAWF)
82
20% of bolls open
83
30% of bolls open (nodes above cracked boll NACB)
89
90% of bolls open
91
10% of leaves discolored or fallen
92
20% of leaves discolored or fallen
96
60% of leaves discolored or fallen
97
Above ground parts of plant dead; plant dormant
99
Harvested product (bolls and seeds)
1 Side shoot development may occur earlier. If there is a vegetative side shoot, continue with principal growth stage
2. If there is a reproductive side shoot (fruiting branch), continue with the principal growth stage 5. 2 Pin-head square or match-head square ist he first square witch forms at the first fruiting position oft he first fruiting branch.
Reference: Munger P., Bleiholder H., Hack M., Hess R., Staub T., van den Boom and E. Weber 1998: Phenological Growth Stages of the Cotton Plant (Gossypium hirsutum L.) Codification and Description according to the BBCH Scale. Journal of Agronomy and Crop Sicence
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