Probably more than for any other vegetable, respecting the principles of crop rotation is fundamental in the case of yellow onions. It is better not to plant yellow onions on land that has just been smoked (with a high nitrogen accumulation); they will not like it at all!
It should not be planted after a green manure crop (clover, vetch…) or beans, peas, broad beans, plants which all have the capacity to fix nitrogen from the air and return it to the soil.
In which soil to grow yellow onions ?
Grow yellow onions in a loose, light, well-drained soil, without fresh manure. It fears clayey soils and heavy soils. It develops better in siliceous or silico-clay soil.
Before sowing, you can spread a fertilizer (100g/m²).
Under which exposure should yellow onions be grown ?
Yellow onions can be grown in all regions of France, even in mountain gardens. They are particularly well suited to a mild, low humidity climate.
Where to plant yellow onions ?
The onion does not like too rich a soil but this does not mean that only poor soil is suitable. No, it is simply that the onion likes to follow the crops of the vegetables known as “roots”: beets, carrots or turnips, when a part of the nutritive elements of the ground is already consumed. As it also likes loose soil, yellow onions can be planted just after potatoes, an excellent vegetable crop (by the way) to “work” the soil without getting tired.
What is planted in the onion?
There are 3 ways to introduce yellow onions to the vegetable garden.
Sowing the bulbs (seed)
Sowing yellow onions is very popular with lovers of delicate tastes. It allows the cultivation of old, uncommon or local varieties. Like all sowing, it is a more restrictive method than the others because it requires careful monitoring.
The plantation of the small bulbs is the most traditional method. From autumn in mild climates or at the end of winter elsewhere, garden centers put forward nets of 50 to 100 bulbs of common varieties of yellow onions but certified disease-free.
This method is practical, economical and often provides a better harvest. The yellow onions obtained at the end of the cycle are indeed bigger, especially in regions where the good days are too few for this long-cycle plant. On the other hand, the choice of varieties is much less vast with bulbils than with seeds.
Yellow onions in bunches
Finally, in the spring, onion plants in bunches can be found quite easily (on markets, at local horticulturists) and can be directly transplanted in the garden, as is also the case for leeks. This makes it possible to grow mostly local varieties without the constraints of sowing.
When, where and how to sow yellow onions?
It is during the month of February, in root day if you garden with the moon, that you begin to sow the small early white yellow onions.
Sow directly in dry soil, which is far from obvious at this time of year. Make shallow furrows 10 to 20 centimeters apart. Then cover the seeds lightly and finish with a light watering if the soil is dry.
When the plants are pencil-sized (1 to 2 months later), thin them out to leave only one onion every 3 to 5 centimeters. Recover the surplus to replant elsewhere or share.
How to plant bulbs?
Yellow onions bulbs can be planted in the fall in areas with mild winters. Push them in until the tips are flush with the soil surface and space them 5 cm apart in the row.
In cold regions, the planting period is from mid-February to the end of March.
Planting yellow onions on mounds
Yellow onions do not really like heavy and humid soil. The bulb tends to rot, the seedlings are sensitive to melting. In this case, put up mounds of about 10 cm high and sow or plant them on top. The bulbs will appreciate to have the feet in the dry.
Maintenance of its plantation
As the onion is a slow growing crop, it is necessary to weed and hoe the crop regularly. Otherwise they will quickly be invaded by weeds.
The use of a mulch is possible, but be careful for the plantations of autumn or at the time of very wet spring, the mulch can facilitate the rotting of the bulbs.
Its watering needs are rather low, but it still needs water during its growth. Water if rains are scarce.
Which plants to associate with yellow onions ?
The onion is a threadlike plant that takes up little space in the garden. It is therefore interesting to grow this bulb in the company of other vegetables. There is no shortage of judicious combinations: place yellow onions among carrots, lettuce, strawberry plants, parsley or at the foot of tomatoes.