As Elis says. Change the water for clean each day and cut the end of the stem so that it lasts the longest. (Do not put any acylpyrin in the water or in the bag sold preparations to prolong the life of cut flowers) Chrysanthemums have an exception, in which the end of the stem must break and, for example, in the case of lilac, it is good to knock the end of the stem with a hammer. For roses, make the longest possible oblique cut and especially when you come with it, for example, on a date :) make a new cut just before you put it in the water at home. If the rose already has a bent head (the rose can wither soon), you can save it by immersing it in water for several hours. (for example in the bath) Roses also cannot be in the same water as any other flower, they must be in a vase separately. If you buy a tied bouquet of a combination of roses + other flowers, it will not be pretty soon, because the roses will wither in it. Chrysanthemums (November) also do not belong in mixed bouquets. They will last a very long time, but the other flowers, which will be in the same water with them, will wither again. Well, for example, meadow flowers (with the exception of daisies) unfortunately do not have a long shelf life. And that's a shame, I like you the most: D