Tulips signal the arrival of spring with their bright colors and profuse blooms. Left to their own devices, they may spread to a wider area, but they may also become overcrowded and cease to bloom. Tulips must be divided on a regular basis to keep them bright and vibrant.
Transplant tulips in mid-summer or fall after the foliage has died back. Once tulips bloom, it is vital that you allow them to grow undisturbed until the leaves turn yellow and eventually die. This is the period of time when the plant is working hard to store enough energy to live through the winter and be ready to bloom again in the spring. Disturbing them before they have had adequate time to store energy may cause next year's blooms to suffer and may even kill tulips off altogether.
Dig deeply around the perimeter of your tulip bed to determine the depth of the bulbs and the extent of the roots. When you lift your bulbs from the soil, you want to do so without disturbing or damaging the root system and bulbs.
Lift bulbs with a spade and and gently shake loose soil from the roots. Be careful not to damage the roots in the process.
Prepare a bed of loose soil for your tulips that is at least 10 to 12 inches deep. Add compost or other organic matter to the existing soil and work it in well.
Dig a hole at least 8 inches deep for each tulip bulb. Add plenty of peat moss to improve drainage and to retain moisture.
Add a low nitrogen bulb food and work it into the soil. Some tulip growers prefer to add the bulb food to the top of the soil after planting the bulbs and working it into the top two inches of soil.
Plant your tulip bulbs to a depth of 8 inches and cover with soil. Firm the soil down with your hands and water throughly.
Consider planting some of your tulip bulbs in the original bed when you transplant them. If they do not do well in the new location, you will still have some tulips that will produce well until the others grow accustomed to their new location.
Keep the bed moist for the next few weeks to give your new bulbs a good start.