May is a key phase for onion development, as it determines how much energy the plant can invest in the growth of the bulb and not in the green stem. A comprehensive supply of nutrients is essential for large and juicy onions.

Here are the most effective fertilizers for May:

Classic: NPK 10-20-30
In May, it is recommended to reduce the nitrogen content and focus on phosphorus and potassium.

Phosphorus: Supports the development of the root system and bulb structure.

Potassium: Regulates the water balance of the cells – this makes the onion particularly juicy and allows it to be stored well.

Home Miracle Remedy: Wood Ash and Table Salt
Many experienced gardeners swear by this natural combination that not only nourishes but also protects.

Wood Ash: It is rich in potassium and micronutrients. Simply sprinkle it between the rows and work it into the soil.

Table Salt (in moderation!): Dissolve 1–2 tablespoons of salt in a bucket of water. This is said to repel onion flies and supposedly makes the crop sweeter and juicier. Important: Use only once per season!

Ammonium Nitrate (only if the stems are yellowing): If the onion stem is light green or yellowish in early May, it still needs nitrogen. Water with a weak solution (1 tablespoon per 10 liters of water), but stop at the end of May, otherwise the onions will grow slowly and the bulbs will remain small.

What else should you look out for in May?

Task: Why is this important?

Thinning: If the bulbs are planted too close together, they don’t have enough room to grow.

Watering: Consistent moisture is important for a succulent texture. Don’t let the soil dry out completely!

Mulching helps retain moisture in the soil and suppresses weeds.

Tip: Always fertilize after rain or a thorough watering so that the active ingredients reach the roots and don’t harm the plant!