Why Do Onions Bolt Prematurely? Causes and Control Measures
After onion seedlings are planted in autumn or spring, through growth in spring and summer, the above-ground part grows 9~10 leaves, and the underground part forms a bulb, namely the onion head. However, some onion seedlings, after transplanting, can still produce a few leaves, and bolt prematurely before the bulb forms. This phenomenon is called premature bolting, and it can seriously affect yield and quality. So what causes premature bolting in onions? How should it be controlled? Let's take a look together.
I. Causes of Premature Bolting
Different varieties differ in their sensitivity to soil temperature. Excellent varieties show high yield and a low bolting rate, while varieties highly sensitive to low temperature are very prone to premature bolting. In addition, how much nutrition the overwintering seedlings accumulate is also a major factor affecting premature bolting in onions. If sown too early, the seedlings grow stout, and the bolting rate rises markedly after long exposure to a low-temperature environment. Also, early planting results in a higher bolting rate than late planting. If sown late, the seedlings are small, but planting too early can also raise the bolting rate.
II. Control Measures
1. Choose varieties with strong winter hardiness
Because varieties with weak winter hardiness are sensitive to low temperature and can accept low-temperature vernalization while the seedlings are still small, while varieties with strong winter hardiness are more sensitive in their response, they are less prone to premature bolting.
2. Sow at the right time
Sowing at the right time is also an effective measure to prevent premature bolting in onions. Sowing too late very easily causes premature bolting in spring, and sowing too late very easily leads to seedling death during overwintering, with extremely low yield.
3. Plant at the right time
If planted too early, although the seedlings are not large, they can still continue to grow when the temperature is relatively high after planting. When the seedlings reach the temperature required for vernalization, it will cause premature bolting in spring, so onions must be planted at the right time.
4. Select seedlings strictly
When planting, be sure to choose seedlings 12~15 cm tall, with a pseudostem 0.5~0.8 cm thick, free of pests and diseases, and 50~60 days old. If you choose stout-growing seedlings, you can set them aside for a few days to inhibit growth, and then plant them, which can reduce premature bolting.
5. Control excessive growth reasonably
During the onion seedling stage, control fertilizer and water to avoid excessive seedling growth; set them aside for a few days to inhibit growth, and then plant them, which can reduce premature bolting.
6. Remove the bolt in time
For plants that have bolted prematurely, the flower stalk should be removed promptly from the base of the flower stalk.
The above is an introduction to the causes of premature bolting in onions and the control measures. We hope it can help you. To learn more related knowledge, please stay tuned to us.