Crown Imperials (Fritillaria imperialis) are impressive plants. These spring flowering bulbs have been cultivated since the 16th century. They produce a stalk in mid-spring that quickly grows to a height of three to four feet. At the top of the stalk is a crown of nodding, bell-shaped flowers topped with a pineapple like tuft of bright, glossy green leaves. These flower clusters last for about two to three weeks. The downside of crown imperials is that the bulbs smell like a skunk. The upside is that the skunk smell tends to repel bulb eating critters from your flower bed.
Crown imperials are hardy to zones five to nine. In the north, they should be grown in full sun. In the south, or in hot regions, they require partial shade.
Crown imperials need moist, fairly rich sandy soil that drains fast. You can assure this by tilling up your flower bed to a depth of six inches, then covering it with three inches of compost. Till in the compost until it is well mixed into the soil. This adds rich organic matter that helps the soil drain and makes it rich enough for the crown imperial.
Crown imperials tend to start producing roots while still in their package, so should be purchased and planted early in the fall. To plant the crown imperial, prepare the flower bed as mentioned above. Then add a two inch layer of fine gravel at the bottom of the hole to prevent root rot. You should also add some bone meal to the hole. Place the bulb on its side, on the gravel, so that the bottom of the bulb is eight inches deep. Then fill in the hole.
Water in well, and water regularly throughout the growing season. Reduce watering when the Crown Imperial goes dormant. After the flowers stop and the leaves die off in mid summer, cut the plat back to just above ground level. Mark the area with a stake or you will lose your bulb. Mulch heavily for winter to protect the bulb from the cold. In the spring, remove the mulch and top dress with an inch of compost.
New growth must be protected from slugs and snails. This can be done by using an iron phosphate based bait such as Sluggo or Escar-go. These are not as toxic as the older, copper based baits.
Propagating crown imperials can be done by division or by seed. Crown imperial plants resent being disturbed, but they can be propagated by digging them up and dividing the babies from the parent bulbs in the summer, after the foliage has finished.
Pot up the smaller bulbs immediately and hold them in a bright, protected area for the first year to allow them to develop. They can then be planted in the fall in the flower bed.
Crown imperials can also be propagated by seed. Strew the ripe sides into flats and cover the seeds lightly with soil. Place the flats in a cold location such as a refrigerator or unheated garage for at least three weeks to stratify so they will germinate. They will germinate in the spring but should be allowed to grow in the flat the first year before being planted in the garden. It can take up to five years to get the first blooms using this method of propagation.