There are 2 main groups of classification, which are split into:
- Perennials (P) – A plant that lives for more than 2 years and flowers / produces a crop every year.
- Annuals (A) – A plant that completes its entire life cycle in a single growing season.
- Biennials (B) – A plant that completes its entire lifecycle over 2 years. So it may grow in the first year, then flower and turn to seed in the second.
How Hardy they are (in other words, can they cope with the cold)
- Hardy (H) – These are frost tolerant plants, and can usually cope with the worst of the British winter.
- Half Hardy (HH) – These are slightly more tender plants, that cope with a bit of frost, but will need protecting over winter – storing the plants in a greenhouse, or covering them with fleece is usually sufficient
- Tender – unless otherwise stated plants are usually tender which means that they do not like frost, and will usually die at the first sign of frost each year.
You will usually find these on the back of seed packets, or on plant labels, and are often denoted by their respective letters. So some examples would be:
- HHP – Half Hardy Perennial. This means that the plant will continue to produce year after year, but will need some frost protection in winter.
- HP – Hardy Perennial. A plant that will produce year after year, and can happily cope with the British winter.
- HHA – Half Hardy Annual. A plant that completes its lifecycle in a single season, and should not planted out until after the risk of frost has passed (tender young plants if Half Hardy will not cope with frost)