Plants occupy almost every environment on Earth, from the waters to the mountains, deserts and bogs. Flowering plants represent a small part of the plant kingdom (They are the division of Spermatophyta) yet they make up some of the most important plant groups. Their life cycle consists of a seed germinating, the plant growing, flowering and dying but it is so much more than that. During a plant’s life cycle they undergo immense changes, from a simple seed, with its tiny embryonic plant inside, to the seedling with its struggling, fast growing cotyledons (seed leaves) aiming for the light, to the flowering plant in full growth before the flowers bursting forth to attract a pollinator. Then the seeds, perhaps contained in fruits which taste good and are dispersed by animals, or stick to coats of birds, mammals and even us as we pass by. Then there is death- the plant has seen to it that its progeny have the best chance of survival and must now leave it to fate – however, plants go to a great deal of trouble to ensure the next generation has every chance of survival.
Flowering plants have several different life cycles. First the annuals who germinate, grow, flower, set seed and die in one growing season. For them, it is vital they produce as many viable seeds as possible as the seed will ensure the next generation of plants. They flower at the height of the good season when most pollinators are around, they are showy and produce thousands of seeds which are dispersed by the wind, eaten or simply drop from the parent plant.
Ephemerals are similar to annuals except they do the complete life cycle several times over one growing season or year.This is why chickweed for example apears to come up so quickly after you weed the ground – you actually bring fresh seeds to the surface towards the light and encourage germination.
Biennials germinate, grow vegetative parts and store food in their roots. They often die down at the end of the first growing season or remain in a dormant form. However, that stored food is put to good use because as soon as conditions are good again (spring) they grow quickly, put on good growth, flower (often early to get the early pollinators and avoid being swamped by trees and taller plants), they then set seed after a long flowering period and they die – all this takes two years or growing seasons. We use this knowledge of the life cycle to our advantage. For example, carrots are biennials and at the end of their first year, they store food in their tap root – we harvest and eat this. If the carrot was left, it would grow again and flower the following spring – at the expense of the root which would turn woody as the energy reserves were depleted.
Lastly but by no means least are the perennials. These plants have a life cycle which persists for more than two years. They germinate, grow, set seed and remain. They may die down if they do not have woody supportive tissue, during the winter but will re-emerge in spring. Some do not die down and these may have woody thickening – these are your shrubs, trees and bushes.
So, what may seem like a simple life cycle is actually one of several possibilities and in each one, the plants have adapted their life cycle so they get the best advantage to continue their species, colonise and ensure the survival of the next generation. Fascinating things aren’t they?