Lewisias (Lewisia) of various species interbreed easily. This accounts for the multitude of magnificent hybrids, which have become so popular in the gardens all over the world. Their flowers come in a range of rainbow colours, decorated with brushstrokes of different hues or brightly outlined veins. The most popular lewisias are those with blooms of white, cream, pink, peach, salmon, yellow, orange and scarlet. Flowers come singly or in inflorescences of several blooms on long stalks. Flowers of some lewisias are sessile, growing straight from the basal rosette.
Lewisias are most comfortable growing in alpine gardens, on slopes, retaining walls or hillsides, where water drains freely after the rain or during a winter thaw. They prefer being given eastern or western exposure, since they scorch easily in full sun. If you intend to grow lewisia on a heavy and waterlogged soil, dig a planting hole about 0.5 metre deep, spread a layer of well-draining material and top up with porous and fertile soil (e.g. a mixture of well-rotted compost, peat and sand at the ratio of 3:1:1). Mulch with gravel, since the leaf rosette is very prone to rotting, especially when water gets inside the rosette and stays there for a period of time (after a long rain, etc.). Mature lewisias dislike transplanting, so plant them in a position, where they are to flower. In winter lewisias tolerate cold, but not winter thaws. Use conifer branches or clean, dry leaves to insulate them, and cover up with a pot or some other kind of shelter.
Most species of lewisias, especially the Siskiyou lewisia (Lewisia cotyledon) hybridize easily and tend to mutate, therefore a seedlings of a pink flowered plants can easily burst into white or pink flowers. If you are after a ‘carbon copy’ of the parent plant, propagate lewisias by offsets, which are cut off and rooted. Sometimes all offset rosettes are in flower, and therefore unsuitable for propagating. In such case, remove all flowering stems as soon as possible, so that the rosette puts a spurt of growth, until it can be divided and rooted. Plants are best divided in late June, and within 4 to 6 weeks they will be rooted.
Lewisia brachycalyx cultivars do not produce any side shoots, but they grow several replacement leaf rosettes from the underground rhizome. These lewisias are easily propagated by rhizome divisions, provided each piece has at least one bud. Divisions should be dipped into rooting hormone and potted. Sometimes these particular lewisias are very slow to produce any replacement rosettes. In such event, the professional growers nip off the top of the main plant, and wound or pierce the thick root in several places. It might take a whole year for the new offsets to grow, but they are usually numerous.
Although lewisias prefer moist soil and warmth during the period of active growth and flowering, they will tolerate drought and heat. During an extended dry spell plants may go dormant, bursting into new growth only the following spring. Do not try to revive them by watering or transplanting – they will most likely rot. With the onset of cooler weather, lewisias might break dormancy and start growing again. If plants are container-grown, they can be simply moved into a shadier position.
Lewisias grow well in pots or miniature portable rockeries, since this way they can be moved under the roof and kept dry during winter. Pots have to have drainage holes. A planting mixture of fertile compost and sharp sand (4:1) is ideal. Container-grown lewisias should be transplanted every year, replacing potting soil each time, and given liquid feed a couple of times during the growing season.
Saw-toothed lewisia (Lewisia serrata) grows best in a permanently moist situation, but it dislikes winter thaws. Its seeds germinate easily, and seedlings are low-maintenance. Leaves are deeply serrated, and leaf rosettes are beautiful even when out of flower.
Lewisia brachycalyx leaf rosettes and flowers dislike wind and water, so they tend to rot when grown outside and hardly ever flower. Therefore they are best grown in pots, where they can be overwintered inside, somewhere cool and light. Leaf rosettes disintegrate (leaves roll up and turn jelly-like) after plants have finished flowering, and new growth appears only next year. They need some moisture in autumn and winter, when they produce underground buds. Once a month a pot should be submerged into water for half an hour, and left to drain afterwards.
© Mygarden.lt, 2011