Plant Life Cycle
An individual plant starts out life as a small seedling, cutting, offset, etc.
This plant has to grow to a certain size before it is able to flower and fruit.
Plants that grow naturally in areas with dicernable seasons often use seasonal cues to start their growth.
For example, after a cold winter, the seed of a temperate climate plant may start to germinate when warmer spring weather arrives.
If this is an annual, the plant will grow quickly, flower and set seeds.
By then, the annual will be exhausted and will die.
Biennials will grow for one season and store food reserves.
They will go dormant during the winter, or the dry season.
Then when conditions are more favourable, they will sprout using the stored food, flower, set seed, and then die.
Perennials, on the other hand, make slow and steady growth, always storing food reserves and / or growing bigger.
A few will flower in the first season, most will flower from the second season, but some can take many years to start flowering.
After flowering and seeding, perennials usually have enough food reserves to keep growing and flower again the following season.
Cinerarias provide a flush of colour in spring.
Spring annuals start out life as germinated seedlings in late summer or in the autumn.
These usually put on some growth in the autumn, remain dormant through the winter and then burst into flower when spring arrives.
By summer, the plants will have gone to seed and died.
Because spring annuals have to grow through the winter, they may not be suitable for areas that experience very cold winters, and is certianly unsuitalbe where the ground remains frozen for long periods in winter.
In areas with mild winters, it is possible to grow summer annuals as spring annuals by starting their seed in mid to late autumn.
These plants will grow through the winter, like their spring annual cousins, and also flower in the spring.
It also may be possible to germinate quick growing spring annuals, such as cinerarias, in late winter, and have them flower in the spring.
These plants will often be smaller and will produce fewer flowers.
Summer and autumn annuals
Cosmos and provides lots of
colour in summer and autumn.
Summer and autumn annuals germinate in spring or early summer.
Plants from temperate areas over winter as dormant seeds.
In the garden, a wider variety of annuals can be grown, because seed from plants that normally grow in warmer areas can be started in the spring and grown as annuals.
Annuals are quick growing, and a good supply of moisture and fertiliser is essential during the growth phase.
Once they have started to flower, fertiliser can be reduced.
Certain drought resistent annuals, for example, Cosmos, do not require a lot of water or fertiliser.
In frost free areas, it is possible to extend the flowering season through to early winter.
The seeds are sown late, around late summer or early autumn.
The plants will grow and start to flower in late autumn / early winter.
Most will last through the winter if it has not been too cold.
Ephemerals are a special class of annuals that grow very quickly, flower, seed, and are gone as quick as they arrive.
Most come from harsh environments where there may only be a very short period of time for the plants to grow and seed.
For example, most dessert wildflowers will lay dormant as seed in the sand until it rains.
Then the dessert is transformed into a sea of green, then into a riot of colour, and at the blink of an eye, the plants seed, wither, die and the dessert returns.
Ephemerals provide quick colour and versitility.
They can be quickly grown to fill a blank spot.
To grow these plants successfully, it is important that plenty of water is made available during the growing season.
It is equally important to regularly sow small batches of seed to supply replacement plants that wll ensure continuous flowering.
Biennials are plants that live for two seasons.
In the first season, they grow, then become dormant in the winter.
Then in the next season, the plants will flower, set seed and die.
Sometimes, a short lived perennial is grown as a biennial, for example, the foxglove.
It normally lives only 2-3 years, and usually exhausts itself flowering that often, the plant either dies or the second flowering season is very poor.
It is often better treated as a biennial and replaced after flowering.
Biennials are usually grown the same way as annuals and are also replaced after flowering.
They have to be started one season before they are expected to flower - think of them as long growing annuals.
There is another class of biennials, those that have a distinct leafless dormant period.
An example is the onion.
The seeds germinate in the autumn and the plants grow through the winter and spring, storing food and water reserves in a bulb (the onion).
The leaves then die down in the summer.
The next autumn, new leaves will sprout, fed by the bulb, and the plant will flower, set seed then die.
A perennial is a plant that lives for more than two years.
To support the longevity, the plant grows an extensive system of roots.
Therefore, it is very important to dig the soil deeply and incorporate plenty of organic matter before perennials are planted.
Perennials may be either herbaceous and woody.
Herbaceous perennials do not grow any permanent woody structure, with yearly new growths replacing older ones.
Perennials may be either deciduous or evergreen.
Deciduous perennials have some form of food and / or water storage organ usually below ground, for example, bulbs, corms, tubers and roots.
During the growing season, the plants feed the storage organ.
Then when cold weather or drought conditions arrive, the plants pull nutrients from the leaves, lose the leaves and become dormant.
The stored food then feeds the plant when it sprouts during the growing season.
Perennials that lose their leaves in the winter will usually need a layer of mulch to protect their underground storage organs from heavy frost.
Leaving the dead tops on until spring usually affords an extra level of protection.
These perennials usually sprout in the spring and may be damaged by late frosts and some form of protection may be necessary in some areas.
Feed these perennials in the spring as this is when they make the most growth.
In the summer, switch to a fertiliser that is low in nitrogen and none at all in the autumn.
This helps the growth harden in the autumn, in preparation for winter.
These perennials may also require watering in the summer to grow and flower well.
Cyclamens grow through
Perennials that lose their leaves in response to drought will usually start their growth in the autumn and grow through the winter.
The colder soil locks up phosphate and these plants will usually benefit from an application of super phosphate in the autumn.
Sometimes the growth starts underground, as in the case of spring bulbs, and nothing is visible until winter.
These perennials usually do not require any watering as their growing season coincides with the wetter months.
An evergreen perennial
grown as a deciduous.
Evergreen perennials usually come from areas where the conditions are more or less stable all throughout the year.
Sometimes evergreen perennials are grown outside their natural range, and find themselves stressed by environmental changes.
These plants may then drop their leaves in response to the stress and behave like deciduous perennials.
This behaviour sometimes prolongs the life of the perennial, by stopping the perennial from flowering to death.
Most perennials flower for many seasons, but a few only flower once then die, for example agave and most bromeliads.
Shrubs and trees
Most people will not normally associate shrubs and trees with perennials, but in fact, they are actually woody perennials.
They can be either evergreen or deciduous.
Most New Zealand natives are evergreen.
In favourable conditions, they grow throughout the year, only slowing down in the winter.
Deciduous trees and shrubs, on the other hand, go completely dormant in the winter.
As gardeners, we can take advantage of this dormancy.
For example, the usual time to move deciduous trees and shrubs is when they are dormant.
Deciduous trees provide the perfect shade - shady in the summer and sunny in the winter.
Spring bulbs can be planted under deciduous trees.
They grow then the trees have shed their leaves.