True poppies belong to the genus Papaver, which encompasses many species and cultivars. These include some of the most beautiful flowering ornamentals for a garden. Some, notably Oriental poppies and Iceland poppies, make good cut flowers for indoor display. The tall varieties are useful for sunny borders where the soil drains freely. The dainty alpine poppy (P. alpinum) responds to conditions similar to rock gardens.
There are annual, biennial, and perennial poppies. They come in many colorful shades of pink, salmon, carmine, scarlet, crimson and white. Many have black at their centers, but some, such as the Shirley poppy, lack the black markings and so appear more delicate.
Among the numerous poppy species and cultivars on show at the 2016 Impressionism exhibit were the Shirley poppies, a horticultural strain of Papaver rhoeas, the poppy of Flanders fields, which grow 1 foot - 2 feet tall, with blooms 3 inches or more in diameter. They were developed by an English amateur gardener, the Reverend W. Wilks, from a single plant of P. rhoeas that he chanced upon in a field. Shirley poppies do not like to be transplanted, so sow seeds in early spring, Cover to a depth of 1/8 inch, and keep them there to grow undisturbed. If they become crowded, thin seedlings from 9 inches to 1 foot apart. Cultivate the surface soil between them shallowly to admit air and discourage weed growth. If plants need support, place branches inconspicuously inserted into the soil near them. Deadhead to prolong the blooms through the season. With the onset of hot, humid weather flowering is reduced and blooms soon fade.
Oriental poppies (Papaver orientale) were also on display in the conservatory. They are stately, hardy, herbaceous perennials and are very showy. They can grow to 2 feet - 3 feet from the ground and feature bright, crepe paper-like blooms. Although admired for their gorgeous blooms and foliage, they can fade in high summer and need neighboring plants that sprawl or cascade to hide unsightly plants. Oriental poppies flower in June, along with bearded irises and early perennials, such as lupines. Orientals come in deep blood red to mahogany red, claret red, orange red and exquisite pinks (salmon) to white. Flowers range in size from 5 inches to 8 inches in diameter. Some have double blooms.
Grow these poppies in well-amended soil, incorporating compost or well-rotted manure and some bone meal at least 1 foot down. Transplant poppies in summer when they are young, without foliage, spacing plants about 1 1/2 feet apart. Newly planted oriental poppies take hold rather slowly and usually bloom better the second summer. Stake plants to withstand windy conditions. Plant singly or in groups of three a little distant from the border. In cold climates, provide a protective winter cover of salt hay or evergreen boughs.
Iceland poppies (Papaver nudicaule) are among the daintiest of the group, lovely for garden and cut flower arrangements. A few of these were featured in the exhibit. They are popular for their many colors, including yellow, orange, apricot, pinks and white. Some are double-flowered. The flowers, growing on wiry stems, can be 4 inches - 5 inches in diameter. They are considered perennials but are best treated as biennial plants, with superior flower display in the second summer. In late spring or early summer, plant seeds thinly in a sandy mixture, protect, and grow in a cold frame or outdoors. Transplant strong good-sized seedlings 6 inches apart, in sunny, well drained soil.
The alpine poppy (Papaver alpinum) was not represented in the Impressionism exhibit but is in a class by itself. These miniature poppies belong in a rock garden, where the environment meets their needs. They can also be planted atop a planted wall or between the crevices of flagstone paving where roots can reach the porous stratum beneath. This species likes limestone soils. Amend soil as needed. They do not like to be transplanted, so sow seeds where they will remain.