| 
Adapted and translated from CETIOM (1995) by P.D.Hutley-Bull.
The lifecycle of the sunflower is divided into 6 numbered phases, each associated with a particular kind of activity. Each phase is divided by a decimal point into numbered steps marking the progress of development within each phase. These together constitute the growth stage.
The first phase is designated 0 and covers activities taking place before the emergence of the crop; the remaining phases are designated 1 to 5 and cover the rest of the lifecycle.
In the binary system, GS 5.1 is further divided into three smaller steps, allowing the progress of the crop to a harvestable condition to be estimated in the field.
Phase 0 Germination
Phase 1 Emergence and expansion
 |
1.0 Emergence; the crook of the seed stem (hypocotyl) appears above the soil |
 |
1.1 The seed stem straightens and the two seed leaves (cotyledons) and first pair of true leaves unfold |
Phase 2 Vegetative growth
| |
2.1/2 Each of the first pair of leaves reaches 4 cm (1.5") in length and the leafstalks (petioles) can be identified. A further pair of leaves is visible to these and at right angles to these. |
 |
2.3-2.4 The next two leaves reach 4 cm (1.5") in length and their leaf stalks (petioles) also become visible, while further leaves appear within these, creating the apical rosette. |
| |
2.5 The fifth leaf reaches 4 cm long and its leafstalks become visible
|
| |
2.n The nth leaf reaches 4 cm long, and its leafstalk becomes visible. |
Phase 3 Growth of the flowerbud
 |
3.1 The flowerbud (inflorescence) can just be seen in the middle of the apical rosette of leaves. |
 |
3.2 The flowerbud becomes separated from the apical rosette and its bud-scales (involucral bracts) are readily distinguishable from the juvenile leaves. Its diameter, including bracts, is not more than 2 cm (just under an inch). |
| |
3.3 The flowerbud becomes fatter and grows clear of the final leaf. Its diameter now falls within the range 5 - 8 cm (1 - 2"). |
 |
3.4 The flower bud is still vertical but standing quite free of the leaf rosette and with a diameter of 5 to 8 cm (2 - 3"). The centre is still closed and the outermost budscales are beginning to fold back. |
| |
3.5 With the spreading back of more bud-scales, the yellow ray florets are now visible within, though initially quite pale in colour. |
Phase 4 Flowering, pollination and seed production
 |
4.1 The ray florets are now beginning to unfold and are soon perpendicular to the plane of the disk (capitulum); at the same time, the neck (the to of the flower stalk) begin to grow unevenly, causing the flowerhead to incline. |
| |
4.2 The neck becomes more curved and the flowerhead continues to expand until its ray florets are fully spread. At the same time, the anthers of the three outermost rings of disk florets start to release pollen, though the stigmata are not yet visible. |
 |
4.3. The three outermost rings of disk florets now become functionally female with the loss of anthers and the emergence of the receptive stigmata. More pollen is released by the anthers of the next three rings of disk florets. |
| |
4.4 Seed production is now underway in the three outermost rings of florets, with stigmata visible in the three next inwards and active anthers in the three rings lying within these. The most mature seeds are light grey and still quite soft.
|
| |
4.5 The remaining disk florets are now active and the ray florets are beginning to fade. The seeds in the outermost circle have become darker and their skins harder. |
Phase 5 Seed maturation
|
5.0 The ray florets have been shed, but the back of the disk is still green. |
| |
5.1 a) The back of the disk begins to change through lime-green to lemon, though the bud-scales stay green. Seed moisture drops to 50 per cent.
b) The back of the disk has faded to pale yellow, as have the bud-scales. By now, senesence has overtaken around half the foliage leaves. Seed moisture is typically about 40 per cent.
c) The back of the disk has become a rich yellow and the bud-scales are mottled with brown. The disk itself has begun to dry out and its moisture content is now less than 80 per cent. Seed moisture is down to 30 per cent. |
 |
5.2 The back of the disk is deep yellow and the bud-scales are brown almost to their bases. Drying of the disk tissues is well advanced and two thirds of the leaves have senesced. Seed moisture content has fallen to 20-25%. |
|
5.3 The back of the disk is now marbled with brown, the stem tissues are drying out and the budscales are totally brown. Seed moisture is around 15%. |
 |
5.4 The whole plant is dark brown and seed moisture no more than 10%. |
| |
A Summary of Sunflower Binary Growth Stages for UK Use.