New bed for cutting flowers?

[WaitingForSummertime]

I've got a triangular patch of ground about 5 x5 x 7 metres and next spring I'd like to turn it into somewhere I can plant flowers I can cut for the house in the summertime (not necessarily next summer!). I'd love at least two or three peonies, and a hydrangea and I tend to like white and pale pinks. Has anyone got any recommendations for varieties, and perhaps other plants that would work and I might like? Is that enough space do you think? It's a very sunny, sheltered spot in the summer, although won't get much direct sun in winter when the sun is low. SE of England. I can also be quite forgetful, so the more plants look after themselves the better😁

That sounds quite big for a cutting bed. I like combinations of corn flowers, pot marigolds and love in a mist, as well as pansies and verbena. They will seed themselves to some extent although obviously not in a regular way that’s typical of cutting gardens.
Do you like dahlias? The bishop varieties are popular, and in the South you probably don’t need to dig up for winter.
National Trust gardens usually have cutting gardens you could study. They tend to start with Siberian irises and run through to dahlias.
Alliums can be quite dramatic. Sun flowers need some support usually.
Some grasses would be useful and maybe an evergreen such as pittosporum.
I find sweet peas quite hard work because they are very productive.

Oh, cornflowers! I remember being given a patch of my dad's vegetable patch when I was a kid and filled it with cornflowers which were glorious!

Looking again at your post, cosmos is supposed to be the most productive cut flower and you can get white and pink ones. There is a bit of a tension between things that look after themselves and things that make good cut flowers because obviously you need to keep cutting them to get them to produce more flowers. Sweet peas are very productive but I find them a bit overwhelming.

I like gaura because it seems to go on forever without being cut. I think some people do use it in arrangements though I’ve never tried. I grew it from seed. ‘The bride’ is a good one.

Cosmos is lovely and comes in many colours.
Japanese anemones come late in the season, and look pretty. Cerinthe is very easy to grow.
Sarah Raven has a whole section on cutting garden flowers on her website.

Cosmos and cornflowers are lovely! Take a look at Higgledy Garden website. he has some brilliant cutting garden flower ideas and his seeds have always been very reliable for me.