People are often worried about having deep borders because that means more planting. Some come to me because they do not have the first clue about plants, especially how to look after them, so they initially shy away from lots of planting. However, my experience has been that these same people by the time we have worked through the design process together, they have taken a shine to their new garden and are really bonding with their plants. Some even help with the planting!
So, I say, bigger is better when it comes to borders. Deeper borders give plants the space to breathe and to show themselves in their best light. You only have to look at the borders in various country gardens to see how this works to best effect. Deep borders give impact to your garden through planting in swathes or layering so that you have successional flowering and interest all year.
So how deep is deep? A border should be at least 1.5 m depth. Any less and the plants will be in a single line. Think of a plant, say Astrantia, which has a spread of 60 cm and you want to put another plant behind that has similar spread - that’s the depth of the border almost full. But you don’t have to limit yourself to 1.5 m deep!
So what are you waiting for? Now is a great time to expand your existing borders and create new ones - just remember, be generous and you’ll be florally rewarded!