Mike Lyle writes
Sue wrote:
[...]
I think you're right to go for plugs or small plants if you're trying
to get more wildflowers into an already grassed area. You can always
have a go at growing some extra ones yourself in trays to keep costs
to a minimum. I found it easiest to clear small areas of turf to give
the new plantlets room to get a start before the grass closed in
again. Once they've established they'll seed around on their own.

But if the area has grass, you can forget about any massed effects with
most wild flowers. Meadow flowers will establish, and still look very
nice, but the grass will dominate. Among the best competers for more
striking effects I remember ox-eyes, and the little wild daffodils, too.
My bluebells-in-grass experiment hadn't really got going before I had to
move, but they seem to do well in some exposed grasslands.

Cowslips and field geranium have done well with me, on rather rich
grassland on damp clay.

In high nutrient conditions, grass is a very effective competitor, so
you need to try to reduce the fertility, for example by always taking
away the grass cuttings and, of course, never, ever, feeding.

Crocuses aren't native, but the more delicate species ones fit in very
well.
--
Kay