In article , Janet Baraclough
writes

The message
from "Anne Marshall" ] contains these words:

Hi, My garden has never been cultivated as it was previously a garage.
The ground is extremely wet - most of bulbs planted last Autumn have
rotted. I dug in quite a lot of horse manure in the Autumn and added
some topsoil.

Look at gardens either side of you to see if they are waterlogged. If
not, one possibility is that the ex-garage area isn't draining because
it's so heavily compacted by being driven over; it may even have a layer
of hardcore beneath it.

You could ask a builder to excavate a test hole to see what the
situation really is. If there is a load of hardcore, it may be worth
employing a contractor to remove it all - and then to replace it with
good quality topsoil.
You might even dig the test hole yourself - if this seems either fun or,
at least, a better option than going for a workout at the gym!
--
Chris