Posted: 03/12/2012 at 13:19
Wow that is quite a large area. Glyphosate mentioned by Nutcutlet is a weedkiller that does not harm the soil. It is one that is taken in by the roots of the plants you wish to get rid of and kills them but does not last in the soil so you can plant it up as soon as the weeds die. It is best applied in July/August when the plants/ weeds are growing freely. I agree with Welshonion - try to clear a small area at a time. One thing you can do with the area you wish to save for your greenhouse/ patio is to buy a large quantity of weed suppressing fabric and once you have cut back and levelled the area cover it completely wuth the fabric the hard standing for the greenhouse and patio can then go on top of the fabric.This means that that section of ground will not need to be treated so saving you the expense of glyphosate.
Bracken is a native British fern and is common in moorland areas. Unfortunately its spores and bits of its roots can be transferred to gardens in potting compost but at least when the first little leaves appear it is easily dealt with. It is poisonous so wear gardening gloves when handling it just to be on the safe side. I do hope this helps Andrew but you can always send another message on here.