With its beautiful silvery leaves and showy blossoms, purple sage makes a superb addition to drought tolerant plantings.
Under quasi-desert conditions, purple sage is a dense rounded 3-5 ft (0.9-1.5 m) semi-evergreen shrub. In an irrigated garden, it is inclined to be a more open 5-8 ft (1.5-20.3 m) plant. It has 0.5-1 in (1.3-2.5 cm) felty wavy-looking ovalish alternate leaves with silvery pubescence. The five-lobed tubular 0.5-1 in (1.3-2.5 cm) flowers are borne singly in the leaf axils. They have spotted throats and a typical foxglove family character. The flowers appear after summer rains, sometimes covering the plants with white, pink, lavender, purple, or blue blossoms for a spectacular week long display. Two-valved capsules filled with small wrinkled seeds follow. 'Alba' has white flowers, whereas 'Rain Cloud' has violet-blue. 'Green Cloud' produces green foliage and pinkish flowers. 'Sierra Bouquet' bears lavender-blue blossoms on plants with very silvery leaves. Pink flowered 'Compacta' is a smaller variety used for low hedges and foundation plantings. Relatively evergreen 'Bertstar Dwarf', which is sold under the name "Silverado Sage", has a rounded 4x4 ft (1.2x1.2 m) form and is exceptionally full and dense even at the base.
There are several similar Leucophyllum species , but the literature is confusing as to just how many and which varieties represent which species. Here is a reasonable guess at how they sort out: Barometer bush (L. minus) is a small twiggy shrub with violet flowers from the Trans-Pecos region; the variety 'Silver Cloud' has silvery white leaves and dark blue flowers. L. violaceum is a purple-flowered species from the Chisos Mountains. Violet silverleaf (L. candidum) is a very dense shrub represented by two noteworthy varieties: 'White Cloud' has pale gray leaves and light blue flowers and 'Thunder Cloud' has intense purple flowers and a more compact shape. 'Lynn's Everblooming', a cultivar of L. langmanae, is a low growing dense gray-green shrub that produces lilac pink flowers most of the summer. Chihuahuan rain sage (L. laevigatum) is a more open shrub with up-turned branches and small flowers. Blue rain sage (L. zygophyllum) is a small, dense, very slow growing plant that takes shearing well.
Purple sage comes from shrublands on limestone slopes in the Chihuahuan Desert of Texas, New Mexico, and northern Mexico. It is now widely cultivated in Florida and Southeast Asia, where it flowers magnificently in steamy tropical weather.
Purple sage grows best in gravelly limerock soils, but it isn't picky about pH. This species does not like fertilizer or compost and will be reluctant to bloom in rich soil. The plants tend to sprawl and get leggy as they age. To prevent this, keep the soil dry and lean and tip prune to encourage dense foliage and compact branching. Purple sage grows slowly, so hedges of this species do not require very frequent pruning.
Light: Purple sage prefers full sun, but can get by on 4-6 hours of direct sun per day. Moisture: Purple sage must have exceptionally well drained soil. Water it conscientiously until it is well established, then treat it like the desert plant it is. Overwatered plants will get floppy and resist blooming. Hardiness: USDA Zones 7 - 10. This species is hardy to 10ºF (-12ºC). Plants may survive temperatures down to 5ºF (-15ºC) or lower, but they will drop their leaves. They bloom best in hot, humid weather. Propagation: To grow purple sage from seed, press the seeds into moist soil, but do not cover them. They will germinate in about a month. To propagate this species vegetatively, take 4 in (10.2 cm) cuttings of new growth in the summer after the plant has flowered and insert them in a rooting medium composed of half perlite and half sphagnum moss. Keep them moist (but not wet!) and they will root in a few weeks.
In its native Texas, purple sage is often grown in big pots flanking the entrance to a driveway. It is also a good choice for foundation plantings, hedges, barriers, windbreaks, or screens. The dried leaves and flowers can be brewed into a pleasant herbal tea that is said to be mildly sedative and good as a bedtime drink or for treating colds and flus.
Purple sage is one tough plant! It can face droughts, freezes, high winds, salt spray, hungry deer, and blazing heat and keep right on performing beautifully.