what's the difference between a polytunnel a cold frame and cloches

[mememe72]

I know this maybe a very stupid question but i do not have a clue what the difference is between each of these things and different people keep telling me different things and thing are getting all very confusing what do you need the different things for and do I need any or all.  Sorry I know I must sound really daft but i really do not have a clue.
Thanks

[mememe72]

[Peasticks]

A polytunnel is a walk in affair with polythene stretched over big arches made of metal or wood, door at one end (or both ends if you are feeling flush or clever with making stuff  :)

A coldframe is a wooden or metal frame with a hinged lift up glass/polycarb lid - this is used to harden off plants or to grow more tender plants such as melons they are usually under 2ft tall and about 2.5ftx4ft in size

A cloche is a mini tunnel or plastic jobby that covers plants in situ, usually curved and 3ft+ long, a bell cloche does the same sort of job but is a dome of glass or plastic. Cloches are normally for keeping plants protected from the weather however a cloche frame can also be covered in fleece or netting to keep off pests.

All are useful in their different ways - I guess it depends on what you want to grow and how worried you are about eating all of it!

[kt.]

A poly-tunnel is a plastic sheeting version of a greenhouse.  Used the same way as you would a greenhouse.

A coldframe is a small box type frame with a glass or clear plastic lid.  It can be made of these on all sides too if you wish.  Once seedlings have germinated,  you put them in as coldframe to free space in the greenhouse and to harden them off before planting outside.  They are usually left in here to grow to a larger size before transplanting.  Coldframes can be any size you wish.  Mine are made of wooden frames with a double glazed unit as the lid.

Cloches are usually plastic of glass. I use plastic bottles with the bottoms cut off and keep the lids off to allow ventilation.  Place the cloche over a plant once planted into its final position to encourage growth.  It acts as a mini greenhouse and can be removed once the plant grows  and touches the sides of it.  

I have just purchased 3 plastic cloches from B&Q,  about 2x4ft.  Once I plant 4-8 plants in the ground, I will place this over the top to speed up and encourage growth.  Once they are large enough or I put in the next lot of plants,  the cloche will be moved around to the new plants.