The black tulip, also known as the "Queen of the Night" tulip, features deep purple petals that look black in low and indirect light, such as the light at dawn or dusk, in shadows, or on a heavily overcast day. Black tulips usually bloom later in the season than other tulips, so a bit of careful planning is required when incorporating black tulips into an existing tulip garden. Once black tulips are established, however, they require the same care as any other tulip or perennial that grows from a bulb.
Growing healthy black tulip plants starts with choosing healthy bulbs. Choose black tulip bulbs that are firm to the touch and feel slightly heavy. Avoid bulbs with obvious bruises, soft spots, or blemishes. Purchase black tulip bulbs in late September to early December, and plant them as soon as possible after purchase. Tulip bulbs should be planted in fall, but no later than first frost, for best results. However, avoid planting black tulip bulbs while the weather is still warm. Too-warm weather will encourage black tulips to flower as soon as they're planted, which puts the plant in danger of frost.
Plant black tulip bulbs in full sun to light shade, choosing an area with moderately well drained soil. Add sand, peat or vermiculite if needed to increase the drainage in clay or decrease it in sandy soil. Plant black tulip bulbs in individual holes or a common trench six to eight inches deep. Black tulip bulbs planted in extremely sandy soil may need to be planted slightly deeper, at eight to 12 inches deep. The bulbs do well in clusters of about 10 to 25 bulbs each, planted 4 to 6 inches apart.
After planting black tulip bulbs, cover the bulbs with soil and water thoroughly. Unless the weather is particularly dry, a single watering will sustain the bulbs until spring without encouraging them to flower in the wrong season. After the first light frost, cover the area in which the bulbs are planted with up to three inches of organic mulch. Peat moss, straw, and discarded evergreen branches all make good mulch to protect black tulip bulbs through the winter.
In the spring, remove the mulch when the black tulip bulb shoots are one to two inches high, and water thoroughly if spring rains are scarce. Black tulips typically flower in their first year after planting and need little care after the mulch is removed. When the petals begin to drop from the flowers, cut off the flower heads to prevent the plant from creating seeds. The energy needed to make seeds depletes the tulip's bulbs of necessary food, making it more difficult for the bulbs to survive the winter.
To transplant black tulip bulbs, dig them up when the plant's leaves turn yellow, usually in early fall. Gently remove loose soil and store the bulbs in a shady, protected area for one week to help them dry. Then, remove any remaining leaves and pack the bulbs in a shallow tray containing dried peat moss, vermiculite, or sand if transporting them. The packing medium helps prevent the plants from drying out. Plant the bulbs in their new location in late September to early December, as in the original planting.