AFRICAN HEMP/Sparmannia africana
From Southern Africa, Sparmannia africana is an evergreen, multi-stemmed shrub which can grow to 6m (19ft) in its native habitat; as a houseplant, however, the restrictions of tub culture and the annual pruning regime keep it at a more manageable 2m (6ft) or so. The genus has a general common name of Indoor Linden, a name which indicates its family relationship to the Lime. This plant is grown for its striking, apple-green foliage, which has an almost translucent quality, and for the delightful white flowers that dot the plant in Spring and early Summer. Each petal is about 2cm (3/4in) long, and the flowers have red and yellow stamens. These pretty blooms appear in great hanging clusters that are spaced intermittently over the plant. This is an excellent cool conservatory plant, or one for a spacious and well-lit hallway; given the space, the leaves may grow to measure 23cm (9in) across.
Grow the African Hemp at a minimum Winter temperature of no less than 7°C (45°F); cooler conditions are preferred, especially in Winter, although some central heating is tolerated. Provide good, draught-free ventilation in periods of hot weather. During the rest period (April to June), keep the plant cool – it can be placed outside during a warm Summer, but bring it indoors before any frosts threaten.
Grow this plant in full light from Autumn through to the end of the flowering period; for the rest period, keep it in the shade.
The African Hemp needs plenty of water when in full growth; reduce the water given to a minimum during the rest period, then gradually increase it again as the plant begins to grow. Use tepid water.
For much of the year, and if grown in cool conditions, the African Hemp has no need of any additional humidity; the difficult period is when the plant is moved from the fairly moist outdoor air to the dry air of the living room in late Summer. Place the plant on a tray of moisture-retentive pellets; do not mist the hairy leaves.
Feed this plant every week from June through to August; if space is limited, try giving it a half-strength feed, changing to a full-strength feed if the leaves turn pale green.
Grow the statuesque African Hemp in a free-draining, loam-based, which will also provide the plant with stability. Repot it in June – at the end of the rest period – and prune it back to around 20cm (8in); by September, it will have grown about 1.5m (5ft) and be ready to resume life as a houseplant.
After flowering, cut back the flower stems to en-courage a more compact growth habit. The African Hemp is easily propagated fromtaken in late Spring.
Pests: Whitefly love the African Hemp: watch for the clouds of tiny white moths and treat any infestations with a suitable insecticide. Aphids and Thrips can also cause leaf distortion and mottling.
Pollution: The leaves of this plant are sensitive to air pollutants: carbon monoxide, gas fumes and smoke will all cause damage to the leaves.
Yellow leaves may be caused by over- or under-watering, by using cold water, or by a lack of food.