Extract from ‘Your Own Allotment’

The life cycle of a plant [focussing on those that give us our food] involves the following stages:

• Pollination
• Fertilisation
• Fruit and seed growth
• Seed dispersal
• Germination
• Growth

Then it starts again. 

Our actions as food producers on our allotments can affect each of these stages, and our outputs are dependent on the successful completion of each stage; so an understanding of each is very helpful.  I will go over each of these at a high level.  If you want to go into it in any more detail then check the bibliography at the end.

Pollination

Plants have two important parts that are engaged in pollination – the ‘male’ part – called the anther; and the ‘female’ part – the stigma [note the sexist naming].  Pollen is transferred from the anther to the stigma by a variety of processes in order to fertilise it.  These include:

• Wind
• Insect
• Self-pollination
• Water
• Other animals

Wind pollination – Those plants that are pollinated by wind are easily distinguished from those using insects because, as they do not have to attract insects, they have not developed all the interesting characteristics of insect pollinated flowers. [see table below].  They are often dull to look at or to smell, by comparison with those that rely on insects.   Grasses, cereals and many trees are wind-pollinated. 

It is a wasteful process in terms of amounts of pollen produced to actual seed that ‘takes’ or germinates: but still nonetheless efficient when measured by plant success.  More effort is put in to producing great quantities of pollen for blowing in the wind [as Bob would say], rather than interesting things [nectar, smell, colours] to attract insects; and which we enjoy so much.  The reproductive parts are outside – to release the pollen and to catch it as it floats by or falls down.  Some species have male and female trees – eg holly.

Examples of wind pollinated plants include all grasses – eg sweetcorn, wheat, and others such as beetroot. 

It is the vast amounts of pollen produced by these plants that cause hay fever for some people.

Insect pollination – Many plants have developed an extremely successful and mutually beneficial relationship (symbiosis) with insects [bees, moths, butterflies, beetles, etc] that carry out the pollination for them. 

The plant secretes nectar to attract them and is also usually prettily coloured and sweetly smelling, again to attract them.  The insects benefit by getting nectar as food – and the plant benefits by being fertilised.  We benefit from this working relationship as we can enjoy the beautiful colours and smells, as well as eating the produce that results – and if you like it – the honey made by bees. 

Bees

The most useful insect in the UK for pollination is considered to be the bee; which of course uses the nectar, not only as food, but also to make honey [a store of food or energy – which we can also enjoy].  A bee’s favourite colour is blue – so old-fashioned geraniums, lavender and cornflowers amongst others are excellent for attracting them into your allotment.

The insects are attracted to the flowers and, in order to get at the nectar, they enter the flowers where it is stored.  As they do so they brush against the anthers which are covered in pollen.  The pollen sticks to them – either because it is sticky or ‘hooked’ and then, after they have sipped the nectar, they fly off and go to another flower.  It may be on the same plant or another one.   When they enter another flower then this time the pollen they collected from the last flower rubs off onto the stigma – and they collect another load of pollen for the next flower; and so on. 

Note that the pollen must come from the same species or the fertilisation will not work generally speaking – although cross-fertilisation does presumably take place sometimes to provide a crossbreed.

Those plants that rely on moths often have rather pale coloured petals that show up rather better at night – and smell nice then as well.  At dusk, if you are lucky, you may see the humming-bird moth.  This a large moth that hovers, just like a humming bird does, as it takes nectar and pollinates plants.

Examples of insect pollinated plants are cabbage, courgette, leek, peas [what would our gardens and allotments be like without peas and sweet-peas?], pumpkins and squashes, runner beans, sunflowers.  Apples usually need pollen from two other cultivars [types of apple] for real success.

Self-pollination – Some plants do not need outside agencies – they are self-pollinated.  Examples include lettuce, tomato [in UK – but in its natural habitat it uses bees], french bean and many soft fruits.

Water – Some plants produce pollen which floats on water to other plants – eg ribbonwort- but there are not many of these.

Other animals – Some flowers are pollinated by other animals – eg humming birds and bats; the process is broadly similar to that for insect pollination.

Pollen

We think of pollen as yellow – but it can be any colour including white, black, orange, purple and it comes in all shapes and sizes. 

You can apparently identify a plant from the colour and shape of the pollen; presumably with a magnifying glass or microscope – should you wish to!

Fertilisation

Once pollination has taken place and the pollen is on the stigma the next stage occurs.  The pollen grain ‘comes alive’ and sends out a tube which grows down to the ovule; and male nuclei travel down it to join with the female cell and transfer genetic material to fertilise it.  You can tell when fertilisation has taken place as the plant sheds the petals.  They have served their purpose and it does not want to support them, as that would take energy from the next phase – fruiting. 

It will not shed them all, however, just because one has been fertilised.  It will support both fruit and flowers at the same time – in order to set more fruit.   To create larger fruit – pinch out flower buds from a plant; so that it puts effort into the fruit already ‘set’.

Fruit setting and seed development

Once fertilisation has taken place then the plant gets cracking on producing its fruit.  A fruit, however, is not what you and I might call a fruit – and includes many things that we call vegetables.  The word vegetable has no definition whatsoever in botany and is just a culinary term – for those plant things that we eat as an accompaniment to, say, meat or fish.  A fruit is not a vegetable to us and vice versa – that is broadly how we define them. 

What is a fruit?

In biological terms, however, a fruit is the thing produced by a plant that contains its seeds; and includes berries; pumpkins; chestnuts; pea pods; pears, apples and cherries; as well as sycamore, plane, lime and ash ‘helitocktocks’. 

The honesty flowers in dry arrangements are in fact the fruits: the papery thin silvery circles contain the seeds.

The seeds are usually contained inside – but can be outside – eg strawberries.  They can be a separate fruit – apples, lemons; or grouped together – raspberries, blackberries. 

They are divided into two main types – fleshy fruits and dry fruits. 

Fleshy fruits are the ones we most associate with the term fruits – eg luscious to eat. 

Dry fruits are those we usually class as nuts or legumes [beans and peas].

A berry – is a fleshy fruit without a stone but which usually has lots of seeds – examples are kiwi, banana, currant, pepper, coffee, tomato as well as those with the word berry in their name. 

A drupe is a fleshy fruit with a single stone – the seed – and includes plum, cherry, coconut, damson and sloe, olive.

Fruits such as apples and pears are called pomes [from the word for apple].  They have thin coverings, concealing the flesh, and the seeds are inside chambers in the centre of the fruits. 

Just to confuse you Hesperidiums are berries with thick rinds – oranges, limes lemons, grapefruits – all citrus fruits. 

Further confusion comes from the fact that the strawberry in biological terms is a ‘false fruit’ as the seeds are on the outside!

Fruits may contain:

• one seed – many nuts, plums, olive;
• a couple of seeds – grapes, sweet chestnuts;
• several seeds – lemons, apples, pea and bean pods, berries, peanuts, honesty;
• sometimes a great many seeds indeed – pumpkins, melons, tomatoes, squashes.

The fruits can vary in size from very small – the individual parts of a blackberry; to the biggest in the world – a pumpkin – which can weigh in at 220 lbs [100 kg] or more!   Note the UK record is a staggering (literally if you are carrying it) hernia inducing 900 Lbs!!!!!!!

The seeds also vary in size: from those which you can hardly see – to that of the ‘coco-de-mer’ which can be up to 45 lbs [20kgs] and a group of those would do serious damage to your table!

The largest fruit in the UK is probably the conker – the fruit of the horse chestnut.

In the diagram some examples of different sized seeds are given [carrot, melon, squash, bean]

There are lot of very confusing names for different fruits – drupes [eg plum], achenes [eg sunflower, nut], as well as samaras, lomentums, siliques, dehiscent, even indehiscent – that expose themselves all the time – but I won’t go into those.

They come in all sorts of different shapes – pips, flat, round – and the seed containers vary enormously.

Types of seed container

There are many different seed containers including:

Fruit – apples, oranges, strawberries, tomatoes, squash, pumpkins, melons;

Nuts – acorn, chestnut, hazel, peanut;

Pods – beans, peas, laburnum;

Flowers – sunflowers, carrots;

Stem pots – poppy, onions;

Helicopters – lime, ash, plane, sycamore.

Once the plant has produced its fruits with its seeds – which will eventually, it hopes, grow into new plants – it needs to get them into the best places to take root and grow.  They need to be dispersed far and wide in order to achieve their goal of total world domination by plants – or it seems that way with the billions of seeds produced by some plants.

Seed dispersal

One of the reasons for producing seeds is, not only to ensure that the next generation is successful, but also that bio-diversity is encouraged and cross-pollination takes place.  This makes plants [and indeed anything] stronger.  One of the ways of ensuring this is to get the seeds that are produced to travel as far as possible away from the parent [and ‘siblings’].  This is seed dispersal.  It also reduces competition locally for food, water, light etc and reduces the incidence of a disease in one spot wiping out all the plants.

The commonest methods of seed dispersal are:

Natural – using natural events

• wind – the seeds are very dry and light and can be blown a surprisingly long way by the wind.  In some areas the plants have adapted to mature just when the windy season arrives.  Typically thousands of seeds are produced to ensure success.  The most successful trees in the world [pines] use this method – producing millions of seeds from their pine cones.  Others include dandelion ‘clocks’, cornflower, honesty, the carrot family and several other trees. 
  
  Some such as the sycamore, plane, and ash have extensions which act as parachutes or wings to catch the wind and you can often see them spinning gracefully around [helicopters or helitocktocks as my daughters used to call them when they were little].  Thistledown produced by Cardoons is also wind dispersed and that and other down-producing plants yield the ‘fairies’ that float like gossamer and which children love to chase.
  
  Poppies have a curious bulbous head, just below the flower, with holes in it.  As the wind blows it from side to side the seeds spill out.  You can see this on a windy day if you are lucky; and it is one of nature’s great sights.  If you have a video camera; film it and then play it back in slow-motion to get the full and fantastic effect;
• Explosions – some plants have special seed cases which, as they dry out and are knocked, shatter or explode – scattering the seeds over a wide area.  Good examples of this are the legumes [peas, broad beans], laburnum, lupins, broom, euphorbia, gorse and geraniums.  When harvesting peas it is not unusual [Tom] to see pods at the mange-tout stage, edible pea stage and also at the dried up, waiting to explode stage;
• Water – some plants live by the sea or streams and produce seeds that are water proof and spread that way.  They can travel many – in fact thousands of miles.  The best known example to most of us is the coconut.  Willows can often be found by streams in the UK, and their seeds are waterproof so that they can float gently down on the water until they come to rest on a bank, germinate and take root.  You can often chart the course of a stream or small river by the willows along its banks. 
• Catapults – Ferns use water in a different way.  They are curled up when in a dry state and when water is absorbed – eg after rain – their fronds unroll throwing out seeds like a catapult;
• Rock and roll – seeds are encased in coverings that are rocked out of the tree by wind or animals [or boys conkering] and when they land the burst open and the seed rolls along the ground [conkers, acorns] eventually taking root;
• Fire – some plants have adapted to their circumstances to such a great extent that they can only spread their seeds after a fire. [Some like it hot!] The seeds and roots are fire resistant, but the fire triggers their dispersal and then after they spring up with plenty of nutrients [ash] to help;

Animal mechanisms – plants and animals have often developed a complex symbiosis for distribution [as well as pollination – see elsewhere].

• Fruits of the forest – many plants that we enjoy eating didn’t develop their flesh and taste for us [difficult to believe isn’t it? as we regard ourselves as the centre of the world].  They were developed to encourage birds and other animals such as monkeys – and even fish [there is a fruit eating piranha in the River Amazon] to eat them; which is why they are nice and juicy and packed full of goodness.  The fruit, however, contains seeds with indigestible coats.  This usually allows the seeds to pass through the animal undamaged – often miles away from the parent and wrapped in a good dollop of fertiliser [dung]. 
  
  Humans often don’t eat the seeds [eg apples and pears] and throw them away with, for example, the cores – which also served to distribute them at first. Now they go into a bin [or composter if you are an allotment holder] so it is no longer symbiotic – we are parasites!  Many of the fruits that are poisonous to us are not to animals; and they eat them and disperse them in the same way;
• hitchhikers e.g. goose grass, burdock.  The fruits have hooks which grab onto the fur of passing animals and are usually only detached some time later – again a long way away from their origin.   It is a great game that children have always played – picking chickweed and put it on each other’s or parents’ backs.  It stays there clinging tenaciously until taken off.  You often see these hitchhikers in sheep wool – teasing is the process of getting rid of them.  In older times thistles were used for this – hence their other name – Teazles. 
  
  Next time you go for a walk through undergrowth you may find a plant or seed clinging onto your sock!  Legend has it that this type of dispersal was the original inspiration for Velcro – and you can see that that would make sense;
  
  
• couriers – several animals take seeds sometimes accidentally and put them elsewhere eg Mistletoe seeds are very sticky and get stuck on the beaks of birds such as the Missel Thrush.  The birds wipe them off on trees, where they stick in turn and the seed grows and hey presto the plant – which is a parasite – is nicely in situ to grow; feasting on its host, until cut off by a druid; or a barrow-boy at Christmas.  Many animals eg squirrels collect nuts and then bury them; forgetting where they put them.  The seeds then germinate and grow;

Germination

A seed is one of nature’s true miracles.  From a small – sometimes almost too small to be seen – seed; an often massive plant will grow [from little acorns mighty oaks will spring.]  It is a power house waiting for the right moment; and when conditions are just right; from within the seed the plant will burst out and force its way through the soil and into the light of day.   From a cucumber seed, half an inch big, you can grow plants 7 metres [21’] long or more.  From a tiny grape pip you can grow vines that just spread and spread unless pruned hard every year.

Germination is the process whereby the seed takes root; thrusts its little nose out into the nasty horrible world; and then tries to grow into a big strong plant.  Like all life; a plant’s time on this earth is fraught with obstacles, barriers and things that will try to kill it or eat it – given less than half a chance.  There is nothing that many predators like better than a succulent, young seedling – and they are merciless – and with unerring accuracy zero in on your prized or favourite plants; leaving the weeds standing and untouched.

Some germination times – under the right conditions

One week or less             1 – 2 weeks                      up to 1 month                  over a month

Squashes                          Cabbages                          Rocket                               Parsnips

Melons                              beans                                Parsley

pumpkins                         Radishes                           Celery

                                           tomatoes

The process whereby a seed is transformed from a, usually dried out, bit of its mother into a fully fledged member of the plant kingdom is called germination .  During germination, the young plant emerges from its protective seed coat – ie it grows. 

The process requires several factors to be present for it to happen.  It requires:

• water [moisture],
• food [held in the seed, initially] and
• warmth. 

Some plants perversely require exposure to cold before they germinate – typically those known as hardy [which means that they are tough and can stand the cold!].  Seeds grow into plants in two directions at once: up and down [see below] incidentally spreading out as well in middle age.

The main steps in this process are:

• Moisture absorption by the seed
• Root production
• Shoot production and growth
• Surface breakthrough and ‘real’ leaf production

Moisture absorption

The seed absorbs moisture; which starts the process off by allowing the food reserves of the seed to become available, and softens the hard coating to allow the relevant bits to emerge. 

Some seeds are extremely hard and folklore says that you need to ‘nick’ them to allow them to take in water to get them going.  Others swear by rubbing the seeds gently between sandpaper to roughen up the coating.  Legend has it that Victorian gardeners used to carry pea seeds around in their waistcoat pocket for months until they had been roughened up! 

I have never found this necessary: so I have never done this.  As long as there is sufficient moisture and warmth they usually manage to absorb water [but you may find it helps]. 

Component parts of a seed

This particular process of germination varies considerably from plant to plant [see table].  There are three main parts to a seed inside the outer covering:

• the embryonic root;
• the embryonic shoot; and
• the embryonic leaves

and the details of a typical seed growth cycle are explained below – there are others.

Root production

It first produces a root – called a radicle [but not always on the left]; which grows down towards gravity – no matter which way round you have placed the seed.  This is called geotropism – meaning movement towards the pull of gravity [Greek ‘Ge’ – earth and ‘Tropis’ – movement]. 

It will also produce root hairs and further roots which will anchor it within the ground.  This will in due course allow it to take in water and – through it – the dissolved food [nutrients] that it will need to grow.  See ‘Roots’ below.

Shoot production

Next it produces a shoot [this is called the hypocotyl].  This develops from the plumule, and it is protected by two false, quasi- or proto-leaves, called cotyledons, as it pushes through the soil to get to the surface.  Sometimes [squashes for example] the seed cover stays over the plumule as well for extra protection; and you can see it clinging onto one of the leaves after it has broken the surface. 

Note that some plants only produce one leaf, such as grasses [monocotyledons – those with two are called dicotyledons.  Some have a lot more – eg pines can have up to 8 – and some have none – these are called acotyledons]. 

The plumule grows away from gravity – no matter which way up you placed the seed [anti-geotropism or geo-phobism].  The seed contains enough food for the plumule to reach the surface – provided it isn’t too deep – in a fantastic burst of energy.  

In depth analysis

As a general rule seeds should not be planted at a depth of more than one and a half times its size.  If you do then it will use up its food supply before it gets to the surface and it will die.  The plant cannot make any more food until it reaches the light. 

This is a common cause of crop failures when growing from seed.  It is a fine balance: not too deep or it won’t make it; nor too shallow: or it will get eaten, desiccated by the sun, killed by frost etc.  It is a miracle that it makes it sometimes: and of course many do not. 

Certification

When you buy a packet of seeds and it says that the seeds have been certified – it doesn’t mean that they are mad – but they can be maddening when you are trying to get them to grow!  It means that they have been tested for the probable percentage that will germinate in the right [optimum] conditions [called viability].  Most seed packets will state that the seeds have been tested in accordance with the relevant regulations.  It doesn’t usually state what the % viability is, however, so you can’t audit it for accuracy sadly!  Note, however, that the optimum conditions rarely exist outside of the testing laboratory!

Most seeds sold commercially have a viability close to 100%; but some are not so easy to grow.  Carrots only have a viability of about 65%; and it has proved impossible to give anything to parsnips because their germination is so unpredictable – as I know only too well.

F1 hybrids

Note that F1 hybrids are specially produced from crossing two plants to give a definite output and they are more expensive than non-F1 seeds [note F1 just stands for first generation].  For the allotment gardener these are less satisfactory – as they have a tendency to mature all at the same time [unless you engage in a spot of succession sowing] giving you gluts [nasty!].  

You should also note that seeds from an F1 hybrid will not grow ‘true’.  That is they will revert to the characteristics of a parent, rather than those of the F1 cross you bought last year.  If you don’t mind what the result looks like then use the seeds – but if you particularly wish to have that F1 hybrid; then you need to buy the F1 seeds every year.

Breakthrough

Finally the little seedling pushes its nose [shoot] through the earth’s surface and it can start to use the sun’s energy to make its own food from the nutrients that the root hairs have taken up using the oxygen from the air.  This is called photosynthesis [Greek which means making {synthesis} from the light {photon}].  Many people think that it is only leaves that can photosynthesise – but in fact any green part of a plant can make food [carbohydrates] from carbon dioxide and water using energy from sunlight.  This is effected by the chlorophyll within the green parts [which gives it its colouring – Greek again meaning ‘green leaf’].  

Obstruction!

That is what happens in good fine soil.  If, however, the shoot encounters a large stone or another type of obstruction – eg a membrane or a thick mulch – then it will not be able to go through and will try to go round it.  Whether they succeed or not depends on how far they have to go/grow before exhausting the food supply and getting into the light.  That is the logic behind using membranes and mulches to keep weeds down – by denying them access to the light for photosynthesis.

They are, despite this, incredibly tough, however, and filled with a dynamism and determination to ‘see the light’ brothers!  If you have ever seen a tiny plant pushing through the asphalt on the pavement and looked at how much it displaces to get to the air and light; then you will understand this.  

The cotyledons open up on contact with the light – splitting the seed cover open – and then they turn green; to start the process of converting nutrients to energy using photosynthesis.

True leaves

Next the first true leaves appear above the cotyledons.  This allows it to use the sun’s energy; make more roots, strengthen the stem, grow more leaves etc.  At this stage it is usual to transplant them out if you have not grown them in situ.  Where they are sown in situ then after the true leaves have appeared they are ‘thinned out’ to reduce competition for resources and ensure fewer but healthier, stronger and better yielding plants.

After this the we are back onto the beginning of the life cycle and the plant will, with a following wind and at the right time, start to produce flowers for pollination and then fruit – which in many cases is what you want to harvest.

Other ways of reproducing

Whilst most plants produce seeds – others have ancillary methods of reproducing themselves.  These are:

• Suckers – these are shoots that grow up from the ground but are attached to the roots of the plant.  They often grow more vigorously than the parent and often root if they fall over and touch down.  For control it is best to cut them off below ground.  You can use them to propagate by staking them until they have rooted and then severing them [see runners also]
• Bulbs – these are condensed shoots.  In winter the stalk dies back and the roots shrivel as it sucks the goodness back.  It then stays quiescent until spring.  It is a store of food and allows growth to take place in the following season.  It consists of a modified shoot in the centre protected by overlapping layers [quasi-leaves] and having roots growing at the base.  You set them in the ground and away they go.  Examples include onions, garlic, and of course daffodils, tulips and snowdrops.  They produce seeds as well. 
• Corms are similar [eg crocus] but are condensed stems – a bud sits on the top and roots appear from underneath
• Runners [stolons] are long horizontal shoots that grow along the ground producing roots and growth at the nodes or tip.  Examples of these are strawberries and currants – as well as the creeping buttercup.  They can be many feet long!
• Rhizomes – are stems that grow horizontally underground – for example Mint, Iris and the Dandelion.  They can spread very fast.  Mint is very hard to control because of this.  The best way is to sink a bottomless container in the ground and plant the mint inside it; then chop round it to keep the growth down.
• Tubers – are swollen stems.  The best known being the potato.  Buds appear all over it – called ‘eyes’.  For best results you rub out all except one – or cut the tuber into sections each with an ‘eye’.  [note it can be a swollen root as, for example, is a Dahlia]
• Clones/daughters – some plants produce little versions of themselves and when they touch down they produce roots and a new plant is born.  These can be taken off and replanted to give you free plants.  One of the most common is the spider plant.

Roots

A few words on roots – not roots as in Sam Gamgee’s  ‘Roots and tatties’ but as in the stuff under the ground that supports plants.  The word is from Anglo-Saxon and is related to ‘wyrt’ – or ‘wort’ – plant.  The political word ‘radical’ is from the Latin for root – radix – and was a term for those that wanted to tear up the system by its roots: which is the same root [groan] as the name for the initial root from a seed – radicle.

The two major functions of roots are:

• To take in food – by absorbing water in which nutrients are dissolved
• To anchor the plant in the ground.

They often function in storage of food – and it is often this part that we eat [parsnips, beetroots, carrots and so on].  Some other items that come from roots include liquorice; ginger; ginseng, angelica; and of course the mandrake root [qv] is famous in legend.

Osmosis

They take in water through the root hairs on the outside of the root.  These are very delicate and it is for this reason that you never pull a plant that you want to keep or transplant by the root; as it breaks the hairs off.  These hairs only live for a few days and as the root grows it keep sending out new ones. 

The process by which the plant absorbs water is osmosis.  You can see the effects of this if you walk in wet conditions in leather shoes – the soles absorb the water and your feet get wet.  You can also cause it by cutting off the bottom of a potato; scooping out the centre and standing it is a bowl of water.  Next morning it will contain water as it has been absorbed.  If you leave a towel with its edge just in water then the water will slowly creep up it until it is all wet.

Types of roots

The first root to emerge is called the primary root and it is the radicle of the seedling. As the plant grows it can often send out new root shots sideways – these are called lateral roots.

There are two main types of root systems:

• the taproot system – is where the first [primary] root is the main root – often with much smaller roots running off from it.  these roots can often penetrate very deep indeed.  They can also be the devil to pull out as they can anchor a plant extremely well.  Dandelions are a good example of one of these [as are parsnips and carrots].  As well as anchorage they have a major food storage function
• lots of roots with no dominant root – called diffuse roots.  They spread out and primarily absorb nutrients and give anchorage.  They are often much more shallow than taproots and store little food.

Other types of roots

Aerial roots – where the roots are above the plant and can be seen – eg swiss cheese plants, or ivy where they are used to anchor the plant to walls.

Propagative – these are roots that form on the side of the plant’s roots and then grow up and out to make suckers, which form new plants

Cluster roots – very densely packed roots that do not go very far.  This means that they do not anchor the plant very well – peas and beans have roots like these.

Mycelium – some fungi have a curious root that is a network of fibres.  It grows outward from the centre and the fruiting buds – mushrooms or toadstools – grow on the edge.  That is why you see ‘fairy rings’ in woodland where the mycelium has spread outwards to form a circle.

Parasitic roots – roots of parasitic plants that take in the food directly from other plants [for example mistletoe] are called haustorial [from Latin for water-drawer as in a well]. The same word describes the proboscis [the bit that sucks your blood] of eg mosquitoes.

Root facts

Tree roots can often be as deep as the tree is high – and that can be a long way.  Think about that before trying to pull a large plant, shrub, bush or tree out.

As the roots grow longer – they often get thicker as well – called secondary growth. In this case they usually develop hard woody external coverings which act as a very strong tree structure or tree architecture.  You can often see this where rain or river water has eroded soil; and what look like underground branches [but are in fact roots] are visible – and easy to trip over! 

Most roots however lie relatively close to the surface so that they can easily pick up air and water from topsoil.  After storms you can sometimes see trees that have been blown over – and the roots are most commonly of the diffuse sort, rather than tap roots.  That is why they blew over – they do not go that deep – and the tops of the trees act as sails to catch the full force of the wind.

In Victorian times placing a paving stone below trees was a technique used to limit growth in gardens; as it acts as a barrier to root growth.

Bonsai trees are similarly bred small by keeping roots very small.

Root benefits

The roots of trees and other plants often help in binding soil together.  In many areas [Easter Island for example] where all trees were cut down – the soil was eroded, by wind and rain and the land became uncultivable.  This is still happening in many parts of the world today – especially in rainforests with devastating effects on wildlife as well.

Plants from the legume family – beans peas and so on, have special nodules that absorb nitrogen and then fix it in the soil – thus improving it.  Many green manure crops are grown with this purpose in mind [clover, alfalfa, trefoil, lupin].