Hardiness zones

This is a tool firstly used in America that shows a geographically determined area in which a species of plants is capable of flourishing under the specific climatic conditions of that area. It is mostly used to determine whether or not in that geographical area a particular plant is able to withstand the lowest temperatures during the winter. The temperature scale of hardiness zones is situated between two temperature extremes -54°C to more than 13°C. Most of continental Europe is situated between zone 5 and 10.

The table below shows the hardiness zone according to minimum temperature.

Zone		From	To
0	a	< −53.9 °C (−65 °F)
	b	−51.1 °C (−60 °F)	−53.9 °C (−65 °F)
1	a	−48.3 °C (−55 °F)	−51.1 °C (−60 °F)
	b	−45.6 °C (−50 °F)	−48.3 °C (−55 °F)
2	a	−42.8 °C (−45 °F)	−45.6 °C (−50 °F)
	b	−40 °C (−40 °F)	−42.8 °C (−45 °F)
3	a	−37.2 °C (−35 °F)	−40 °C (−40 °F)
	b	−34.4 °C (−30 °F)	−37.2 °C (−35 °F)
4	a	−31.7 °C (−25 °F)	−34.4 °C (−30 °F)
	b	−28.9 °C (−20 °F)	−31.7 °C (−25 °F)
5	a	−26.1 °C (−15 °F)	−28.9 °C (−20 °F)
	b	−23.3 °C (−10 °F)	−26.1 °C (−15 °F)
6	a	−20.6 °C (−5 °F)	−23.3 °C (−10 °F)
	b	−17.8 °C (0 °F)	−20.6 °C (−5 °F)
7	a	−15 °C (5 °F)	−17.8 °C (0 °F)
	b	−12.2 °C (10 °F)	−15 °C (5 °F)
8	a	−9.4 °C (15 °F)	−12.2 °C (10 °F)
	b	−6.7 °C (20 °F)	−9.4 °C (15 °F)
9	a	−3.9 °C (25 °F)	−6.7 °C (20 °F)
	b	−1.1 °C (30 °F)	−3.9 °C (25 °F)
10	a	−1.1 °C (30 °F)	+1.7 °C (35 °F)
	b	+1.7 °C (35 °F)	+4.4 °C (40 °F)
11	a	+4.4 °C (40 °F)	+7.2 °C (45 °F)
	b	+7.2 °C (45 °F)	+10 °C (50 °F)
12	a	+10 °C (50 °F)	+12.8 °C (55 °F)
	b	> +12.8 °C (55 °F)

This is a very good table to determine the hardiness zone of the area where you live. For example, if you recall, or you can determine the lowest temperature in your area for the last 30 years, then can find out which is your hardiness zone. For instance, mine is 8a. This means that the lowest temperature in my town was -11 degrees. Most of European region are situated between hardiness zones 5 – 10.

Many of the cultivated plants are in fact grown outside their original hardiness zone. Tomatoes cannot withstand frost at all. This makes them a zone 10b plants. However, their cultivated as annuals in other, colder zones. Sometimes if a microclimate is created then the temperature can vary outside the hardiness zone.