Spring in my part of the country starts late in the year.
The heavy clay soil stays wet and cold a long time after winter has gone and we can expect freezing weather till the end of May.

After the first rush of flowers of the snowdrops at the end of the winter we have a continuous flowering of many bulbs and shrubs:

Spring really is a feast of flowering bulbs
Anemone Blanda and the the Daffodils: Narcissus "Prof. Einstein" and  N. "Golden Harvest"  With luck the early Tulips blossom in March: Tulipa Angelique pink 
Tulipa Peach Blossom, dark pink and perfumed Then at the beginning of April the blue Omphaloides Verna blooms and the violets start blossoming. 
Tulips blossom like the Tulips Toronto (more than 1 flower per stem) 

Hyacinths "Amethyst" ,which the mice like so much I have to replant with fresh ones every year, Convallaria Majalis (Lily of the valley) does well on clay but is not rampant Hyacinthoides (Scilla) spp, the Bluebells  like it here as well.

Phuopsis stylosa covers the soil and smells lovely It starts in spring and blooms right into summer till autumn, then it gets a musky smell which not all people will like..
Myosotis - Forget me not - comes in several kinds and different shades of blue

May  has all the flowers above and even more: Ajuga reptans, groundcover and  flowering in blue, Gallium odoratum - ground cover and flowering white and some Peony species - who love chalk and clay

June still has many flowers like the Aquilegia vulgaris, which originally was blue, but when seeding itself comes in pink and white as well. 
The shrub Philadelphus -Jasmine- , white with lovely smell. Deutzia bloom one after the other with sweet scent, the roses start coming into flowering like the white  madame A. Carriere which smells heavenly
Rosa Schneewitchen, has a sweet perfume (in sun only) 
Rosa Low white which I bought as a white ground covering rose but which turned out to be a large pink flowering shrub here on the clay has no perfumebut birds like to build their nest in it.
The old tall Cotoneaster - which grows as tall as a tree and has white flowers now - is visited by hundreds of bees and they make those flowers turn into nice red berries which the birds like, later in autumn
Clematis Nelly Moser (striped, pink) blossoms. This climber has found it's way up into a tree and birds nestle in it all spring and summer
Hosta undulata Albomarginata blossoms in the shadow
Papaver orientale -Oriental poppy
Geranium sylvaticum, a white groundcover
Geranium Phaeum - mourning widow - but this has a problem that it easily gets mildew in dry summers
Centaurea, blue cornflowers will be flowering all through summer, but also is prone to mildew