A few months ago I planted tulip bulbs and they already had a small green peg. I planted them and for fear that they would freeze over the earth I put a bit of bark from the flowerbed. But I see that there is still no nineteen coming out of the earth and now they should be out of the earth a few centimeters ... the doubt is: did I hurt to put the barks ??? Is this why I haven't come out? Will they go out now that I've removed the barks ??
generally the tulips are buried at a depth equal to about their diameter, so that the buds that form must travel at most 7-10 cm before being able to emerge from the earth; if we bury the bulbs more in depth, we will cause a delay in the development of the shoots, because the warmth of spring will take longer to reach the bulbs placed very deep.
If you noticed that the weather was very harsh and the bulbs were already partially developed, you were right to cover them further; they will only take a little longer than usual to sprout; you have done just as well to discover your bulbs now that the climate has returned mild, since they do not need further coverage if the climate is not cold and freezing.
If you feel that your bulbs have been damaged anyway, and that for this reason they are not yet sprouting, then you can try to dig them up gently, to check that they are healthy; after having seen in what conditions they are, without touching the roots in any way, cover them again and wait patiently. Consider that generally in northern Italy the tulips bloom in April, so if in March the sprouts do not yet emerge from the ground, it could only be a little excessive night-time cold.
In general, when the bulbs are planted, a depth equal to that of the bulb's diameter is considered as the level of burial, except in particular cases. For example, bulbous plants with very small underground organs, such as anemones, are still placed at a depth of about 5-7 cm.
Or very, large bulbous plants, such as the amaryllis, are buried with the tip of the bulb outside the ground, so with the upper eye completely in the air.
As you have understood, if the winter climate becomes particularly cold, if the frosts are very intense and prolonged, then the ground is further covered over the bulbs, so that the cold does not reach them.
The bark is an excellent material for this type of mulching, first of all because it is very easily found in the nursery, and then because it is light, and therefore in late winter it can be easily removed with a rake for leaves, but at the same time it plays very well its function of thermal insulation.
Guides often read advice that consists of covering the bulbs with dry leaves or straw, which would be the best materials, when even a single winter causes them to rot, and therefore in spring it is often not necessary to remove them from the ground, as they are becoming fertilizer for our bulbous plants; pity that in the city it is not so easy to find dry leaves in abundance, or straw, and therefore the barks play an excellent role as a substitute for these raw materials that are difficult to find.