Filling two rose beds...

[Ulivio]

Hi everybody

I have to fill two rose borders (very few roses, actually) with some adequate herbaceous.
Conditions: Southern Japan, humid subtropical, acidic sandy soil.
I'm thinking to use Alchemilla mollis and Geranium 'Rozanne' : 50-50.

Now, the question is on the planting distance and therefore the total amount the plants I have to order.
The two borders have a total dimension of 65 m2

Depending what I will find at the Japanese nursery here, I'm thinking to do either:
1) 9cm pots : planting distance 15 cm : 49 plants x m2 : 1617 plants (for each type)
2) 2-3 litre pots : planting distance 20 cm : 36 plants x m2 : 1188 plants (for each type)

Do you think such a planting scheme can work? We aim for a good effect from the first year and... correct number of plants! In the attached picture, a sketch of my thoughts...

Any advice / opinion is more than welcome!
Thanks for reading.
G

[ButterflyLady29]

Small plants grow. Are you leaving room for the mature size of the plants or are you filling the beds based on the pot size? If you consider the mature size of the plants and plant accordingly you can either mulch the open areas or fill them with annuals. It would cost less and will still look nice in a few years.

[imafan26]

geraniums spread close to a meter in diameter and they will get taller as well. If you have tall roses that would probably be all right but the shorter floribundas (91.5 cm) might be overwhelmed unless you are going to keep the plant trimmed back so they do not crowd the base of the roses.

[Ulivio]

Thanks you guys for your opinion

The priority is to have flowers this summer. As much as possible (you know, they are not my borders...)
Small plants grow, indeed. I think I can move part of them next year.

Access and mulching won't be big issues, as 1) the beds are quite long and narrow, 2) we don't have a compost production area on the estate (alas!) and carry on chemical fertilizer.
Geraniums-wise, they WILL grow mad (we are in a subtropical climate here), but I'm considering pre-chelsea crop in mid spring, in order to keep them controlled.

All in all, perhaps I can low the order 8-10% and see how I go (if not enough lady's mantles and geraniums, I can always plant some roses)...