What is your soil like?
Most perennials grow in well-drained soil that doesn't stay wet for long, but there are varieties that tolerate very dry soil (such as baptisia, euphorbia, eryngium, echinopsis and verbena) or really wet soil (including actaea, astilbe, hosta, Iris pseudacorus and zantedeschia). Because most perennials originate from meadow or grassland, they prefer a soil that isn't too rich, but if you're uncertain about your soil type, buy a testing kit and make sure you test in different areas of the border.
4 When would you like the plants to flower?
I love my garden to have flowers for as much of the year as possible, but if you only use it when the days get warmer and lighter, you might as well focus on achieving a wonderful colour splash for those particular months. For instance, if space is limited, don't waste money growing early spring-flowering perennials at the back of your plot that may never be seen but, rather, focus on brightening up the part of your border closest to the house.
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5 Which flower colours do you really prefer?
Just like your home decor, flower colour choice is a personal thing. Most of us have favourite shades and combinations that can be reflected by using a number of similarly coloured plants to create an eye-catching palette. And don't let anyone tell you that you can't put together two disparate tones, such as yellow and pink. If it's what you want, go with it!
6 What do you want flowers for?
Other considerations to help focus your plant list include whether you'd like to attract wildlife with nectar-rich flowers for pollinators, or want to cut blooms regularly for your home. If space is limited, look for long-flowering varieties or those with more than one season of interest. Finally, it's worth looking out for tried and tested plants that have received the Award of Garden Merit (AGM) from the Royal Horticultural Society.