It seems that the only thing likely to make nasturtiums fail in the flowering stakes is being over generous to them. If given too much garden compost or manure, they will produce fat mounds of leaves and few flowers. The seeds of these hardy annuals are happy to just be pushed straight into the earth about an inch deep where they are to grow. They can also be grown from a fleshy rhizome . These are happiest in cool, moist, lime-free soil in shade, but its top growth will prefer at least a little sun.
Nasturtiums love the full sun and prefer sharp drainage.
Plant fat and firm rhizomes in spring for a spectacular display from summer to autumn. Pests and diseases Pests, with the exception of caterpillars and blackfly, seldom trouble nasturtiums. Luckily, these two nuisances are relatively easy to control.