Fragrant stock flower spikes growing in a cool-season South African cutting garden

How to Grow Stocks in South Africa

Stocks (Matthiola incana) are fragrant cool-season flowers usually grown as annuals. Gardening.co.za sells compact bedding types and tall single-stem cut-flower series. Use the linked section for your variety; one generic depth, temperature and height does not fit every series.

Quick Grow Facts

Sow one seed per cell in clean, free-draining mix and cover lightly with fine vermiculite.
Keep evenly moist, never saturated, and move emerged seedlings into bright, cool airflow.
Transplant before plugs become root-bound.
Do not pinch single-stem cut-flower series. Support tall rows with horizontal netting.
Harvest most cut stems when three to five lower florets are open.

Beauty Reddish Purple

Beauty Reddish Purple is a selectable cut-flower stock. Cover lightly, aim for 20–22 C and expect the first germination stage in about 3–4 days under controlled conditions. Space 12–15 cm in a supported cut row or 20–25 cm in a home border. It produces large reddish-purple florets on strong, uniform stems.

Iron colours

Iron Apricot, Blue, Pink, Purple, Rose, White and Yellow are cut-flower stocks. Cover lightly with vermiculite and germinate at 18–20 C. Plant approximately 12.5–15 cm apart in cut rows and provide netting as stems extend. Plants produce strong stems about 60 cm long and approximately 55% double flowers without seedling selection.

Do not advise home gardeners to discard seedlings by cotyledon colour or shape. Selection is a professional technique that can waste viable plants.

Katz

For Katz, cover the seed, keep at 20–22 C and expect about 3–4 days under controlled conditions. Plants produce approximately 81 cm cut stems and flower roughly 8–13 weeks after transplanting. Use 10–15 cm spacing in an intensive supported cut row, or 15–25 cm in a home border. Standard Katz produces about 50% double plants; Katz High Double White can produce approximately 90% double plants.

New Kabuki

New Kabuki Dark Lavender and Lavender are selectable cut-flower stocks with large florets, dense spikes, dark foliage and a relatively fast flowering response. Cover lightly and aim for 20–22 C; initial emergence is expected in about 3–4 days under controlled conditions. Space 12–15 cm in a supported cut row or 20–25 cm in a home border.

Noble White

Noble White is M. incana. Cover very lightly so the seed is dark, germinate at 18–21 C and expect about 4–6 days. Plants reach approximately 80–100 cm. Use 12–15 cm supported cut-row spacing or 20–25 cm in a home border.

Vintage Mixed

Back to growing instructions

For Vintage Mixed, cover the seed and germinate at a cooler 17–20 C; emergence is usually 3–5 days. Plants grow about 38–50 cm high and 30–35 cm wide. Space 20–30 cm apart for compact fragrant bedding and cutting.

Regional South African timing

Winter-rainfall Western Cape: sow in late summer or autumn. Shelter trays from heavy rain and transplant into raised, freely draining beds.
Frost-prone interior: start in late winter under cover and transplant as severe frost eases; autumn sowing is only for protected sites.
Humid coast and KZN Midlands: use the coolest workable window, wider spacing, support and morning soil-level watering.
Hot-dry or subtropical interior: treat stocks as a short winter crop and schedule flowering before spring heat. Shade cloth cannot rescue a crop started too late.

Care, cutting and troubleshooting

Provide full sun, fertile free-draining soil and steady moisture. Avoid late transplanting and high heat, which shorten stems. Support tall rows. Cut into clean water when three to five lower florets open.

Slow emergence often means excessive heat or saturation. Damping-off, Botrytis and downy mildew require sanitation, drainage and airflow. Short stems indicate heat or late sowing; lodging indicates missing support or soft growth. Inspect for aphids and thrips and use only locally labelled controls.

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