Rhubarb stems can be harvested in early spring by grabbing the stems from near ground level and twisting away from the plant so you remove the stem and petiole that attaches to the main stalk. If the large, tall stems you see support buds rather than foliage you should cut these out so that the rhubarb plant does not put energy into making flowers. Every five or six years you should cut your rhubarb plants into halves or thirds with a sharp shovel or ax to thin out the old plants. When you divide the old plants like this you will be renewing the foliage growth so the plants will be less likely to try and bloom. Keep growing, Marianne Binetti