Osteospermum
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Overview:
Osteospermum asteraceae is a bushy half hardy perennial with daisy-like flowers originating from South Africa, and is often grown as an annual in the UK.
They grows to around 600mm (24") high and flowers from July onwards, and require sunny, well drained conditions and protection during winter.
Cultivars with the dark blue centers will stand some frost.
They come in a wide range of colors with new cultivars being bred and introduced all of the time.
Pinks and purples tend to be the most common, however breeding has also produced hybrids in white and shades of yellow/orange.
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The flowers open fully in direct sun, and close each evening.
During dull overcast weather and subject to the strength of the available light, they tend to only partially open if at all.
They are also affected by ambient temperatures, for example, they bloom at their best when the nights are cool, on warm nights flowering will be somewhat reduced.
Cultivation:
Week 8:
Sow seeds under glass at a temperature of 18°-20°C (65°-68°F) on a good free draining compost
Sow seeds on the surface of the compost, then cover them with a fine sprinkling of vermiculite, do not exclude light, and this will assist the germination process.
Germination should take around 4-5 days.
Week 8-9:
Prick out the seedlings into boxes or 75mm (3") pots, and grow on at a temperature of 14°- 16°C (57°- 60°F)
Propagation:
Most Osteospermums are hybrids, so saving seed is not recommended, resulting seedlings will not necessarily come true to the parent plant.
However, if this is not an issue many new colour shades may be produced by sowing saved seed from these hybrids.
Cuttings:
Taking cuttings is the best way to propagate named or specific varieties.
Week 2:
Encourage new growth (potential cutting material) from stored plants by increasing the ambient temperature to 10°-16°C(50°-60°F)
Week 6:
Take tip cuttings from established potted plants.
Ensure that the compost is not too wet as this may cause the cuttings to rot off before they root!
When Selecting side shoots it is best to select non flowering rather than budded or flowering shoots.
If the only shoots available are budded remove the buds and treat them like non budded shoots, but avoid flowering shoots!
Cuttings need to have at least two sets of leaf axils and be 50-75mm (2"-3") long.
Sever the shoots with a sharp knife or scissors just below the leaf node, and strip the lower pair of leaves off.
Dip in rooting hormone to promote the growth of new roots(optional).
Most rooting hormone have an anti-fungal agent in them to prevent damping off.
Hormone powders have a short shelf life so it is recommended that they are replaced each season.
Carefully push the cutting into the compost this will ensure the entire stem is in contact with the compost.
Some people prefer to form a suitable diameter hole with a dibber and firm the cutting in, the choice is up to the grower.
The cuttings will root best with temperatures of 16°-18°(60°-68°F)
Place them in a well lit place, but out of direct sunlight to root.
The cuttings should roots in 3 to 4 weeks.
Once rooted gradually harden them off until planting out time.
Once the plants start putting on growth remove the growing tip to encourage side shoots which will ultimately produce more flowers.
Week 14:
To further increase stock divide potted plants and or established plants in the border, pot them up into individual pots and grow them on in a coldframe until planting out time.
Week 35:
Take tip cuttings from established potted plants.
Planting out:
Week 22:
Plant out when all fear of frosts have passed.
Plant 300mm (12") apart in a warm, sunny location in light well drained soil.
Apply a general purpose fertilizer monthly when plants are in flower.
Dead head regularly to encourage repeat flowering.
To flower under glass from April to July, grow three plants in a 150mm (6") diameter pot of John lnnes No1 potting compost (or similar)
Maintain a winter temperature of 8°C (45°F) and water sparingly.
Week 43:
Cut old stems down to ground level in October.
Use cloches to protect the plants from excessive dampness in winter.