The border that we started last October, to mirror the old autumn border, has been filling out nicely. We made the border the lazy way, with no digging see
here and then left it to stew all winter.
In March, we started planting bits pinched from other parts of the garden - crocosmia Emily McKenzie, anthemis EC Buxton, campanula glomerata, various geraniums, astilbe Purplelanze, oriental poppies, salvia nemorosa caradonna, iris Gerald Darby, hemerocallis, persicaria, hydrangea Magical Amethyst and dahlias Painted Girl & Blue Bayou.
We also sowed some newbies from seed - lupin The Page, verbena hastata Blue Spires, veronica longifolia Antarctica, achillea Summer Berries, sanguisorba menziesii, echium Blue Bedder and various annuals to fill gaps - cosmos, lavatera (disaster...far too big for an exposed site).
Yes we have filled the border pretty well but it's a bit mishmash - we need to link it more to the "old" autumn border which has a good deal more shrubs - hydrangeas, fuschias, grasses. It's quite difficult to strike a decent balance of permanent shrubs / grasses and perennials - not many shrubs like to be surrounded by perennials. For example, conifers will resent it, turning their foliage brown but shrubs such as berberis can hold their own and sambucus can be useful, either cut down hard each spring or with a raised canopy.
For background, red stemmed dogwoods, rosa glauca, deutzia and physocarpus are good choices (we have 5 physocarpus Darts Gold already planted). Focal shrubs could include coloured berberis, cotinus or clipped golden euonymus to make a full stop at a corner or end of the border. Choice of grasses depends on your soil type and personal preference but I would avoid ones that run and choose gentle self sowers like the lovely hordeum jubatum which will gently fill gaps through your perennials without taking over.
All in all, the one thing that I have learnt when planting a new border is that most plants don't mind being moved so don't be afraid to experiment and.....enjoy!