Plants always look better in groups with uneven numbers - it's much better to plant them as 3s, 5s or 7s if you have the space. You do have quite a mix of colours there!

Try to think of when they flower, the heights, and plan it out on a sheet of paper before you plant them. Blue and yellow go well together - so you could plan one section to have the Agapanthus, poppies and blue geraniums there. What colour are the Day Lilies? You'd have to place them according to their colour, too. Yellow - with this group. Pink? with the reds.

The pink geraniums would be fine in front of the Rhodos and Paeonies - but I'dd add some white flowers as well, right along the length of the border. Lots to choose from - depending on when you want them to flower.

There's another thing to help your border look good - texture. It's good to have different shaped leaves mixed it as a contrast of form.

You also need some evergreen shrubs as structure for when the perennials finish.

Grasses would help, too - there are plenty to choose from, and they add movement to a border.

I hope this essay helps! PM me if I can help further - for example, to help with plants that have a long flowering period.

38 feet long and varying from 7 to 15 feet is a lot of border - you're having trouble because you haven't got a "skeleton" in place, and by that, I mean a number of larger shrubs along it which are either evergreen, or bare but woody in the winter. If you can work out what you would like in terms of larger shrubs (things like Pittosporum, Pieris, Photinia, Fatsia, Cotinus, Buddleia, Forsythia, Ribes, Euonymus, Escallonia, Pyracantha, Choisya, Spiraea, Physocarpus to name but a few) and position those appropriately, then the smaller stuff that you've got already sort of falls into place - obviously in front of taller things, and hopefully with leaves and colours that contrast well with the shrubs behind.
What you're trying to do currently is like positioning lamps and ornaments before you've got the furniture and carpets in - think about what I've said, any more help, you know where we are.

I was thinking about the length versus the width? how do you stop it looking like a corridor? Would it be better to break it up in to 1-3 different planting areas rather than one area? also should any openings and path be straight or staggered? Any thoughts Bamboo/Spritz?

Not possible to say one way or the other - it's described as a "side garden", which might mean down the side of the house, or one side of a detached house, in which case, it won't be useful to divide it up, but without seeing the site, can't comment on that really DRc

If Novice111 gets back to us, we could add more thoughts! Yes, I agree with Bamboo - without more info. or a photo, it's hard to make any further suggestions.

Didnt pick up on it being a side garden

Spritzhenry, Bamboo and Drc726, thank you so much for all your efforts of help. I did reply to you, unfortunatly the letter (rather long) and photo I sent are attached to a "New Question" under Spritzhenry, as I hadn't noticed this respond box!
I hope the answers I have given you, the added questions I have asked and the photo of part of the plot, will be of help if you should wish to advise me further or have any other ideas.
Thank you again
Novice 111

I found it - and made a few more suggestions, which I hope will give you some ideas. Good luck!

Thanks so much Spritz. It took me a while to find it on the site but I have noted all the suggestions. Didn't think of Delphiniums (white) and Leucanthemum, good idea. The good luck I think I'll need! lol

You're welcome! Stick around here - browse through a few of the ideas in members' gardens - that will help you, too. Look forward to seeing the results. :-)))