The likelihood is your clover and grasses are rooted in with the plants you want to keep. Couch grass is difficult to eradicate by any means, clover you can get rid of - but it requires effort. You need to dig out as much of the roots as possible, preferably when the soil is nice and moist, loosening the soil around the clover then extracting it carefully with its roots. After that, frequent hoeing and removing the hoed off parts will deal with it, but, at the right time of year (autumn) I usually clear the bed if the colonization of weeds is extensive - I dig up everything that can be dug up, all the ornamental plants as well so long as they're not large, established shrubs. Then I inspect the rootballs of the ones I want to keep, extracting anything that shouldn't be there (couch grass roots, clover roots and anything else I don't want), thoroughly dig over the area removing any roots, then replant the newly cleaned ornamental ones you want.
If possible, it would be good to know what part of the world you're in and to see a couple of photos of the problem, showing the clover in particular. If you're in the USA, the area you're talking about might the size of a field for all I know, which would render the solution I've suggested so far irrelevant.
UPDATE: I've just noticed one of your responses in a comment above says that all the flowers are daffodils. Well, no problem then, if you're in the northern hemisphere - dig 'em all out now and thoroughly dig the bed over, removing all roots. You will need to have those daffs back in place by end of this month though. You might also want to consider planting properly in the bed, that is, plants which at least give ground cover during the time the daffodils are dormant - if you don't plant something in bare soil, nature will, as you've discovered.