Onosma are hardy perennials that range from 15 to 45 cm in height.
Onosma plants bloom in the summer and carry tubular flowers of pink, yellow or white that are surrounded by green calyxes.
Common names of this popular rock garden plant include Golden Drop and Golden-flowered Onosma.
Onosma alborosea photograph by wlcutler.
Onosma javorkae picture by elisabetta2005.
When growing Golden drop outdoors from seeds they should be sown in the autumn. Once sown lightly cover the golden drop seeds.
Onosma genus plants like to grow in sunny conditions and have a preference for a gritty, dry and poor soil.
Indoors it is best to start growing Golden drop and other Onosma about three months before they are due to be planted out after the last frost of spring.
It takes from one to two months for Golden drops to germinate at 10 degrees Centigrade. Once ready transplant Onosma species into the garden with a spacing of 15 cm (small) to 45 cm (large varieties).
In the spring it is best to add manure to the soil around Golden drop, and to mulch with rock chippings in order to keep the roots cool.
Unfortunately Onosma are susceptible to rotting in the winter, so it is best to mulch a second time but with organic matter.
Although perennials, Onosma are short lived. More plants should be propagated to replace them every few years, this can be achieved by taking cuttings of golden drop in the summertime.