RHS Plant Hardiness Ratings - Get Into the Zone

Tuesday, 29 January 2019  |  Alison

RHS Plant Hardiness Ratings - Get Into the Zone

Plant hardiness ratings were first introduced in North America, with the publication of the United States Department of Agriculture’s (USDA) Plant Hardiness Zone Map in 1960.  This was designed to help gardeners determine which plants would ‘over winter’ in their particular area of the vast country of the USA, where there are many different climates, from the almost arctic conditions of Alaska in the north, down to tropical climes of Florida in the southern states.

The Royal Horticultural Society (RHS) produced an updated version with UK plant hardiness ratings which was published in 2012 and expanded the range of temperature guides and the British Isles plant zones, which are now rated in chart form of hardiness.     

The RHS plant chart follows a simple code, with H1a being the most tender types of plants such as houseplants and those grown under glass all year round with temperatures of plus 15˚C.       

 At the other end of the scale, H7 represents very hardy outdoor plants that can survive European temperatures down to -20˚C, such as many herbaceous and woody plants.       

However, most plants fall into the H4, H5 and H6 categories in the UK, but with regional variations depending on where the plant is to be positioned, temperature swings and the growing conditions, so looking for a plant hardiness rating is a good starting point to find the right plant for the right situation.        

There are always different considerations to take into account when selecting new plants for your garden, so choose a reputable garden nursery, preferably local to your particular area and one that nurtures and grows most of their own plants.  Smaller independent nurseries will often stock plants that thrive well in your part of the world and the plant hardiness rating can be a useful guide in helping you decide on a specific plant too, especially if it is an expensive ‘one off’ statement plant or shrub .

Always read the label attached to the plant, which, if it has received an RHS Award of Garden Merit, will have the UK plant hardiness rating on it. The information on the label will give you a good idea of the plant’s attributes as well as how hardy it is.  If you are still not sure, ask for help. If you have picked a good nursery there should be knowledgeable staff on hand able to answer any gardening queries you have.

If you are local to Staffordshire or surrounding counties you are most welcome to pop into our nursery this spring (we are open from 1st March) where you will find a super range of perennials, shrubs and bedding plants and if you need help, one of the gardening team will always be happy to help you choose plants for your garden.  

If you are travelling from afar, we will even put the kettle on for you too and if you are lucky you will get to meet Dave ‘our resident robin’!


Brookside Nursery