Black Velvet Rose Geranium seeds should be started indoors in early spring. Once the weather warms up in late spring to early summer, and night time temperatures are steadily above 10°C (50°F), the curious little seedlings can be transplanted outdoors.
When I Get My Seedling Home
Keep seedlings under very bright light to prevent legginess. Artificial lights are ideal, but a bright (ideally, south-facing) room will work for the short term. You may have to pot on seedlings more than once before they go out to allow for root growth. This is done by transplanting them into a slightly larger container with enough additional soil to keep the container mostly full. Keep the soil moist by daily watering and allow for free drainage so the plants are never sitting water.
Do not transplant outside until night time temperatures are steadily 10°C (50°F) or warmer. This may mean keeping seedlings indoors for up to a month. The plants should not require any fertilizer until transplant time.
Harden off seedlings gradually over 1 week, once night time temperatures are consistently above 10°C (50°F). Geraniums are fairly hungry feeders that benefit from rich garden soil and regular feeding with liquid fertilizer or compost tea. Grow in full sun to achieve the best foliar colour.