This time of year children wonder if the winter will ever pass. You can create your own harbinger of spring. Just cut branches of forsythia and then set them in a large vase filled with room-temperature water. In a few short weeks spring will arrive when the branches green up and burst into bloom. To pull off a similar feat of an early spring, try forcing your own shrubs and trees into bloom between 1 and 2 months before actual flowering time. Good candidates include pussy willow, flowering quince, and ornamental cherries and pears.