Ecologically inspired annual plantings have a more recent history than those that use perennials. Yet they have enormous potential and, ironically, largescale projects may sometimes give better value for money than perennials. Their potential lies with their visual impact and ease of growth. The general public like and, to some extent, expect bright colour from public plantings, which annuals are able to provide. Their rapid establishment from seed and low cost per unit area make them a highly attractive option for managers of open space.
The trialling of annuals and the development of nature-inspired seed mixes was started in the 1980s in the Netherlands by Rob Leopold and Dick van der Burg. They produced a range of seed mixtures based around a number of colour schemes which have proved popular with the general public but which have made little impact yet with managers of public spaces. Quite separately, Nigel Dunnett at the University of Sheffield started trials in the late 1990s, aiming at producing seed mixes that could be used by local government open space managers; a project that has got off to a very successful start with sales having started in 2000.
Dunnett stresses the importance of simplicity in creating the seed mixes, with a maximum of 10 species per mix. A number of the species chosen need to have a reputation for both reliability and a long season of flower, for example Argemone mexicana, Linum grandiflorum ‘Rubrum’ and Eschscholzia californica. Other species can be included for a spectacular but shorter burst of colour, for example Phacelia tanacetifolia, or for late colour, for example Rudbeckia hirta. ‘Emergents’ or taller, more architectural species, add another dimension, for example ornamental grasses or species with attractive seed heads, such as Nicandra physaloides. Variations in the overall effect can be created by sowing different mixtures in bands based on differing heights, flowering times or colours. Biennials or short-lived perennials can also be included if the planting is to be left for more than one year, in which case they will flower alongside those annuals which are able to re-sow in the second spring (Dunnett 1999).