Flowers have meaning, and you can telegraph to someone what you're thinking just by handing them a specific flower. If you want to tell someone you have faith in them, or that they should keep faith, there are at least four different flowers you can use for the message.
Texas A&M University notes that the iris means faith, hope and wisdom, among several other inspirational meanings. The genus name is simply Iris, containing nearly 280 species. Floppy petals in a multitude of colors and patterns attract bees for pollination. The U.S. Forest Service notes that native irises live in every state except Hawaii. A word of warning: Should you decide to present someone with a bouquet of irises and want to gather those healthy wildflowers you see as you walk, ensure you are not on federal land. Irises in national forests are protected, and picking them is illegal.
Both Rose Floral and Victorian Bazaar list huckleberry flowers as another sign of faith. Huckleberry bushes (of which there are several species in the genera Vaccinium and Gaylussacia) are best known for their berries cooked into pies, but prior to developing fruit, the plant produces clusters of blossoms that are white, pink, red or any combination of these colors. Bees love the nectar in the tube-shaped flowers, which hang facing downward.
Note that there is a plant called the garden huckleberry (Solanum melanocerasum) that is not a true huckleberry; this plant has white flowers and small black berries that are toxic when unripe. As the Latin name indicates, the plant is part of the nightshade family and grows in conditions similar to those for the tomato. If you want to give someone a huckleberry bush with white flowers, ensure you know which type of plant you're really giving them.
According to Victorian Bazaar, the compass flower (Silphium laciniatum) also symbolizes faith. The compass flower is a yellow, daisylike flower that grows on a tall stalk that reaches up to 12 feet tall. Each stalk has several flowers. The blooms are about three to four inches in diameter and don't have much of a fragrance. Illinois Wildflowers notes that this American perennial may live to 100 years and quickly bounces back from fires.
The passion flower (Passiflora spp.) is a tropical perennial with purple and white blooms. It is native to the Americas. According to Indiana University, missionaries named the passion flower after the crucifixion of Christ, matching each part of the plant to an aspect of Christ's last days. For example, the flower's corona was the crown of thorns; the vines were the whips used on Christ; and the petals and sepals were 10 of the disciples.