Half circle border planting ideas

Elfer

I have dug up a half circle border in to my square lawn, it has a width of 3.6 m and depth of 1.25 m. I have planted a pink macrophylla at the centre rear border as we already had it in a pot and needed to be planted with a couple of Thuja smaragd of differing heights on either side. The fence is covered by various native trees/hedges which we need to keep for another couple years.

My idea was to plant Hakonechloa macra grass and Hebe emerald green at the front of this half circle in an alternating pattern (I have 3 of each) and then plant 5 Agapanthus (purple & white) behind these but now having second thoughts as I think it might look a bit too formal and wondering if it might be better to plant in groups utilizing some of the other plants below.

I also have 2 x munstead lavenders, 2 x alliums, 2 x Digitalis,  2 x Ilex crenata 25cm balls & 2 x Hylotelephium spectabile stardust that could be used in this patch or elsewhere in the rear border. Yes I know about planting odd numbers 😂

As you have already guessed I am a newbie and this is my first foray into gardening. I didn't really have much to research and plan in advance due to mitigating circumstances but glad I used the opportunity as I am learning a lot already and more importantly really enjoying it.

For this record this patch is west facing and soil is chalky but has about 10 cm of topsoil, I have forked it over, removed 3 bags of stones and applied a 60L of good quality mulch so should be ready for planting after we get some decent rain here in Hampshire. Would really appreciate some ideas on planting configurations 

Loxley

Honestly why not just go for your original idea for now. Yes it will look a bit contrived, but you will soon be able to split the Hakonechloa and the Hylotelephium and then you'll be able to plant in looser groups, 3's and 1's. You'll be able to relocate the Hebes on a more haphazard looking spaced-out configuration of 3. Maybe move one of the larger conifers elsewhere and then move the Hydrangea off centre,  towards where the conifer used to be, in the middle of the gap you created. 

JennyJ

It's a formal shape and the symmetric conifers also give a formal look, so I think your original plan of a formal structure will look good. Also think about what's evergreen (the hebes and conifers, and the ilex and lavenders if you put them in there) and how it will look in winter.

Elfer

I know, my brain is hard wired in such way that finds symmetrical shapes attractive but my heart appreciates asymmetry so trying to diverge from symmetry and keep both happy.

To make matters worse I have a couple of small white panniculata skyfalls on either side of the small Thujas just outside the frame. 🤦🏻‍♂️

JennyJ

If you like symmetry, there's no reason not to go for it with the evergreen structure plants. You could add in some asymmetry with your flowery fillers - the foxgloves, alliums etc that do their thing in particular seasons.

Elfer

I was heading in that direction after your initial recommendation, thanks. I was also thinking of planting a Clematis in order to cover the fencing trelis so as to hide the shed on back of the fence. The part high up on the fence doesn't get much light as there is a big conifer tree as well as a horse chestnut tree. I do have a Koreana Amber arriving next week but think a viticella variety would do better in those conditions, open to suggestions though.