Calandrinia are half hardy perennials and annuals. As the perennials have a short life span they are usually grown as half hardy annuals in the garden.
They are low growing, reaching heights of about 6 to 18 inches (15 to 45 cm) and bloom with hundreds of bright pink and purple flowers from middle to late summer.
Names for Calandrinia include Rock Purslane, Parakeelya and Redmaids. They are ideal, ground cover and edging plants, they can also be used in rockeries.
Plants are able to grow in very hot conditions.
This genus of herbs contains around 150 species and is a member of the Portulacaceae family. Plants are natives of the Americas and Australasia. Some of the commonly grown species of this genus and the countries to which they are native are given below:
As a member of the 20 genus containing Portulacaceae family of plants, Calandrinia are closely related to species such as Pussypaws (Cistanthe), Bitteroot (Lewisia), Purslane (Portulaca) and Fameflower (Talinum).
Common Names: Rock Purslane, Parakeelya, Redmaids, Felton's Flower, Calandrinia.
Life Cycle: Half hardy perennial commonly grown as a half hardy annual by gardeners.
Height: 6 to 10 Inches (15 to 25 cm).
Native: Australasia, Americas.
Growing Region: Zones 3 to 10. As a perennial in zones 8 to 10.
Flower Details: Pink, purple, red, white. Small. Clustered. Raceme.
Foliage: Linear to obovate. Lanceolate. Fleshy/succulent.
Sow Outside: 1/8 inch (3 mm). Following the last frost. Spacing 6 to 12 inches (15 to 30 cm).
Sow Inside: Use peat pots. Germination time: one to two weeks. Temperature 60°F (16°C). Seven or eight weeks in advance. Transplant outdoors following the last frost.
Requirements: Full sunlight. Sandy soil. Gritty soil. Can survive in dry soils. Propagate: leaf or stem cuttings.
If you plan to grow outdoors from seed then Calandrinia species such as Rock Purslane should be sown at a depth of 3 mm after the last frost of spring. If you prefer to start off Calandrinia as seeds indoors then they should be started off about eight weeks before they are due to be put out.
They should be grown at a temperature of 13 to 15°C, and take from one to two weeks to germinate. The seedlings of Calandrinia should be planted out with a spacing of about 20 cm following the last possible frost of spring into an area that receives plenty of sun, and into a gritty or sandy soil.
These plants are very easy to care for as they can tolerate prolonged dry periods. They do not like to much water, especially in the winter. Plants are able to grow as a short lived perennial in warm regions (e.g. Zones 9 and 10 in the USA; Australia) but should be grown as annuals elsewhere. Propagate by taking cuttings or allow plants to self seed in situ.
Calandrinia ciliata – Redmaids
These perennials are short lived and should be treated as an annual in all but the warmest of areas. In the USA they are able to grow successfully in zones 7 through 10. They make idea plants for a rockery and flower in the from the middle of summer through to the start of Autumn with bright magenta colored flowers. They should be spaced at about 6 to 8 inches (15 to 20 cm) apart and reach heights of around one to one and a half feet (30 to 45 cm). These plants are an ideal low maintenance plant as they are drought tolerant and do not require an application of fertilizer; ideally they should be grown in an area of the garden that requires exposure to full sunlight.
Calandrinia umbellata - Rock Purslane
For best results grow in sandy or gritty soils that are of pH 5 to 6; though will survive in other conditions. Plants are drought tolerant and like to grow in full sunlight; it is able to grow at very high temperatures. Plants are low growing (6 inches / 15 cm) and have a prostrate nature; space plants about 6 inches (15 cm apart). They carry pink or purple flowers from the middle of summer.
Amazon USA PDF - Guide to Annual Plants