Time to plant the tulip bulbs? Temperature matters more than the date
You ask exactly when tulip bulbs should go into the ground. In Norrmalm in late September, the time is close. What matters is not the calendar, but whether the soil has actually cooled.
The best time for tulip bulbs is in autumn, when the soil is cool but not yet frozen. This reduces the risk of them starting into growth too early or rotting in warm, wet soil.
Getting the timing right
In your part of Sweden, tulip bulbs are usually planted from late September through October. If it is still unusually mild, you can wait a little, but not so long that the ground freezes. A simple rule of thumb is to plant when nights have become noticeably cooler and the soil feels autumnal rather than summer-warm.
Plant bulbs at a depth of roughly two to three times their height, pointed end upwards, in well-drained soil. If the spot easily becomes wet over winter, improving drainage matters more than planting especially early.
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