Whilst I love seeing the deer there’s no doubt that they’re a real pest if they can get in an ornamental garden. We have two types of deer in our garden, the taller Roe and shorter Muntjac, both of which seem happy to eat almost any plants including ones the internet told me were poisonous to them such as yew… Whilst we’ve fenced the main garden our driveway/front garden is completely open and the deer come in almost daily, and we’ve found plants that the deer (or at least the ones around here) don’t entirely eat. Some they might nibble at, some they’ll eat the flowers but not the foliage, however this means you can have gardens that look like the below without having to fence the deer out.
Let’s start with the flowers spread through the season to give you (almost constant) colour. Spring flowers to start, these three are big impact for a good long period of colour. Sometimes they’ll eat some of the flowers of the Bergenia but not all of them, but the leaves with their great colours aren’t touched. Narcissus and Magnolia I’ve never seen eaten, flowers or leaves:
Bergenia 
Narcissus 
Magnolia (both tree and shrub)
For something more delicate and pan-seasonal I’ve found Ajuga does very well. Moving to early summer these are firm favourites for me but not the deer:
Alliums 
Peonies 
Bearded Irises
Mid summer and I’m giving you three “spikes” options, which are especially amazing planted en masse. These three will self seed and spread well to give a naturalised look. The foxgloves are biennial so make sure to spread the seed at the end of each year for plants the next year and year after.
Foxgloves 
Sisyrinchium 
Salvia forsskaolii
As you move to late summer some more classic ornamentals really come in to their own, they’ll sometimes eat flower heads of verbena or crocosmia, but they’ll not take many and you’ll be left with plenty of blooms:
Crocosmia lucifer 
Verbena bonariensis
The verbena will carry on in to autumn, and along with plants such as stinking hellebores and your foliage choices these will get you through to early winter before hellebores and snowdrops begin to emerge. Foliage choices are generally anything prickly leaved, such as holly or mahonia, but I’ve also found they won’t eat winter box, certain viburnums including “snowball”, and if you like grasses then try Miscanthus as this hasn’t been touched. I’ve incorporated pyracantha as well, which the muntjac manage to eat the lower parts of but anything above two feet seems ok so I now have a lollipop hedge!
Hellebore 
Stinking hellebore 
Mahonia flowers
So as you’ll see you can have many beautiful plants even where deer decide to invade, it’s just about getting plants you like that work with your deer. Give the above a try and I hope they work for you as they have for me! If you need any advice feel free to write a comment and I’ll see if I can help.