The vast majority of bedding plants are half-hardy annuals which are raised from seed for a summer display. This type of plant is sensitive to frost so it is necessary for commercial growers to raise them in greenhouses and then they go on sale to the general public to plant in their gardens when the risk of frost has passed.
Traditionally most gardeners here in the UK have planted their bedding plants out during the second May bank holiday weekend. I believe its the combination of a nation of DIY enthusiasts and the Chelsea Flower Show on TV the same week that springs everyone into action in their garden.
Though saying that I am sitting here writing this post on a bitterly cold day in mid-April with geraniums already on sale due to the sheer number of requests from my customers. But I haven’t had many takers with how cold it is and the fact that we have had a frost nearly every night this week.
It’s a trend I am noticing that more and more people ask for bedding plants earlier every year, but these half-hardy annuals simply do not like the cold and are much better off being left undercover until it is the right time to plant them.