Gardeners World magazine has just reported on an amazing study conducted by the University of Sussex.
Researchers from the university recruited urban gardeners to sow 4-square metre patches of wildflowers like Knapweeds, Campions and Scabious. Here is what they found, the following year:
Bumblebee numbers had more than doubled,
Solitary Bee and Wasp numbers had increased by over 85%.
They concluded; "This project shows that mini-meadows can really help pollinators". The study noted the distinct benefits of native wildflowers over many apparently beautiful ornamental/commercial varieties, for our native insects.
Remember - this is in urban areas, and at the scale of a double-mattress. If you live in a rural or semi-rural setting, or you can spare more space than this, you can expect really superb results from year 1.