I'm a fan of the old sayings, the country lore and one of the guides I go by has always been about March. 'In like a lion, out like a Lamb' basically, if the month starts out rather tempestuous,roaring like a Lion, it will end settled and calm,like a Lamb.
Unfortunately, this year March started pretty settled and inevitably April came in amid grey clouds and following snow flurries. It's not unusual to get late frosts up until May but we have a rose tinted view on meteorologist matters and we tend to find it incredible when the cold weather continues into the 4th or even 5th month.
In reality, it's quite common , hence the dates given by seed suppliers for safe sowing dates for non hardy seeds. They know when the weather can be reliably warm enough to risk our precious little life pods.
The hardiness, or ability to withstand low temperatures, has a recognised scale which is applied to all flora and can be defined by the Royal Horticultural Society as a series of various zones.
Every area across the globe has its own native plants and its own spread of temperatures, and as such each zone reflects the hardiness within that country. As we all love to try and grow the very things we shouldn't, the zones vary from country to country so you can check the zones for your area and find plants that will survive by checking the zones.
Ok, apart from all this talk of zones,what does 'Hardiness 'mean?
There are three degrees of hardiness for the gardener:
Hardy means the plant/seed can withstand seasonal amounts of frost. Seasonal meaning that should we get a penetrating ground frost in mid April that goes a foot into the soil, it may well suffer some damage but that would be extraordinary weather even in this age of extremes.
Basically, Hardy means you can sow or plant when there is still a risk of cold snaps and they need little if any protection. These are or originated from native wild plants or are plants from much colder climates and are therefore used to much worse weather than our temperate country will threaten.
Half hardy means the specimen will survive frost if established but may need some protection when sown. Generally sow or plant after danger of frost has passed and the plant will survive outside happily.
Tender, as the name implies, means the specimen will tolerate no amount of cold. These are ordinarily indoor plants or tropical plants which would need taken in at the first sign of frost.
Many of our annual bedding plants are half hardy, but we don't notice because the process of starting early indoors and then hardening off before planting out, followed by ripping it all out again a couple of months later is part of our culture now,but the indoor sowing and then hardening off is essential with all half hardy plants regardless of your planting scheme.