Hi, these are now renamed Gomphocarpus physocarpus, this is a deciduous sub shrub in its native South Africa, but can be grown as an annual in uk, or grown in a cool greenhouse.
Seed should be sown February to april, on the surface of a slightly firmed, moist seed compost, and lightly covered with fine grade vermiculite, [light is needed for germination, which usually takes14 to 21 days] place in a propagator at 55 - 64f, when large enough to handle prick out into 3" pots, and grow on ,maintaining a temp of about 50f, harden them off over several weeks, then plant out when all risk of frost is passed.
Plant them in full sun, in well drained soil, but give them plenty of water to encourage bushy growth, good luck, Derek.

Many thanks for such detailed info Derek!

You're welcome, Derek.