Tulips can and should only be planted in the Fall, and more specifically from October to mid-December. In order to grow properly, it is important that Tulips have developed roots before winter arrives in full and the frost penetrates the soil. As soon as the roots have taken hold, the bulbs can withstand the frost.
Tulips go through the same cycle every year, and every year the only time that they can be planted is Autumn. Ideally, they should be planted after the soil has been warmed-up from the summer’s sun and then cooled down in the Fall to about 9⁰C / 50⁰F. This temperature is reached at a different time depending on you are, but in Holland (climate zone 7-8) this is from the end of October on. The bulbs should be planted 10 – 12cm (4-5 inches) deep, or twice as deep as the height of the bulb.
After planting, the bulbs should be watered to ensure that root development takes place quickly. As soon as the roots have been formed, the bulb is firmly fixed, and the next phase of growth can start.
The Tulip needs a cold period in order to stimulate later growth, and this process takes place over the winter months. Then, as the temperature starts to rise, the flower gets the signal that it is time to climb above ground. In early spring, the first new sprouts appear as the temperature increases, and they grow, one by one, into the queen of the spring flowers, the Tulip.