Tigridias, also called tiger flowers and Mexican shell flowers, have solid root structures that resemble bulbs. However, they are corms, which are tender and should be planted in the spring after the last frost. Tigridias prefer full sun and, while each flower only blooms for one day, each plant has several flowers that generally bloom on different days.
Turn over the top 12 inches of soil with a garden fork or tiller and mix in about 3 or 4 inches of organic matter such as compost, peat moss or sand. The soil is now more suitable for tigridias. Tigridias like a moist, well-draining soil. Keep the soil moist, no soggy.
Dig a hole 3 inches deep and twice as wide as the tigridia corms. If planting the tigridia in rows, dig a long trench to make planting easier.
Set the tigridia corms in the holes or trenches, spacing them about 6 inches apart with the tips facing up and the fleshy roots on the bottom. If you can't figure out which side is up, lay the corms on their sides and they will adjust to the proper position as they grow.
Backfill with soil and tamp it down so that it is firm and has no air pockets.
Water the tigridias well and cover them with about 2 inches of mulch, such as bark or wood chips, to help the soil retain water.