The Bulb
What is a bulb ?
The bulb is an underground plant-like organ formed by a bud and surrounded by closely-knit, fleshy leaves. These leaves are filled with nutritive reserves which allow it to reform its visible side every year.
To be more precise, the bulb has a short, thick stem and scale-like leaves which protect the flower's embryonic roots. The scales which surround the bud may be tight (amarillis, tulips) or loose (lilly). They contain all the necessary nutritive reserves of the plant.
Their features and reproduction methods diifer according to the type of bulb.
The bulb's hibernating period
Before the blossoming period the bulb is in hibernation, at rest. All signs of life either slow down or almost stop, and the plant becomes more resistant to its surroundings. This may be caused by a decrease in temperature or less exposure to light linked to internal factors of the bulb. Interruption or "waking up" from sleep is caused by temperature, light, chemical substances, etc..
Planting bulbs in Spring or Summer
Bulbs which bloom in Spring like crocii, tulips, jacinthas, narcissii, are planted between September and November, or even in December. Other bulbs like frittulers prefer to be planted from September on. These Spring bulbs like sunny or half-shady conditions.
Summer blooming bulbs like dahlias, begonias, lillies, cannas, gladioli, are planted in Spring, after the last frost. These bulbs are planted in sunny conditions, apart from a few exceptions like the ranunculus and tuberous begonia.
Generally speaking, whether Spring or Summer bulbs, they are planted at a depth equal to twice their height.