I have a very useful little book called 'Plant that Name' by Susan Purveur. It has lists of female names and any plants with the same name. Louise comes up with only Chrysantehmum or Geranium. Louisa however has an Azalea. Don't know if this is of any help. Good luck.

Hi, welcome to GoY, there is a Camellia sasanqua, called "paradise louise" , unfortunately this species is not completely hardy, and would need to be taken inside to flower, which is autumn to winter.
It has been producedby a wholesale nursery in Australia, called Paradise, I don't know if it is available in the uk or not, Derek.

There is a David Austin rose called 'Louise Odier' lovely pink bourbon rose highly scented, I grow it in my garden :-)

Louise Odier (sorry Simbad but it isn't a David Austin rose, it's been around for over 150 years - bred in France) stands the test of time. There is also a Dickson rose called 'Lovely Louise' - can't see a stockist on the Internet, though.
There are several other roses - a nice cream climber is Loiuse d'Arzens.

Sorry Urbanite my mistake I bought it from David Austin many years ago along with quite a few others, ooooops, lovely rose :-)

No probs Simbad - I like DA roses but I can't help but think that a lot of garden centres are doing a dis-service to us by only stocking them and not the hundreds of others. I don't have space to grow as many roses as I would want and a DA rose wouldn't be top of my list (or anywhere near the top)....
One day I will get round to selecting my 8 Desert Island Roses.