Chemical Free Weed Control
Geotextile membranes were one of the great gardening innovations of the 20th century promoted as a chemical free low maintenance weed control solution, used in conjunction with decorative mulches such as bark flakes or gravel.
Generally unsuitable for use in an herbaceous border or where bulbs are planted membranes are primarily found for separation of gravel surfaces from the underlying soil and within mass plantings of shrubs and trees.
In the short term geotextiles can be highly effective at providing a low cost/low maintenance option for these areas but it would be a mistake to believe that they are maintenance free. Typically the kind of issues that may arise are birds disturbing decorative bark mulches thus exposing the underlying fabric and the effect of strong gusts of wind actually lifting the fabric away from where it has been placed.
This is far less of an issue where gravel mulches have been used but other problems can arise. Despite claims to the contrary by the manufacturers in our experience these membranes impede the exchange of air within the soil resulting in the ground becoming compacted, anaerobic, slimy and poorly drained with little beneficial earthworm activity apparent. This does not represent good growing conditions for healthy plants to thrive in.
In the longer term further negative impacts have become apparent. Whenever a mulch is used it will over a period of time trap wind-blown dusty soil particles and seeds, often those of the most vigorous invasive weeds such as bramble, nettle or couch grass. Under these circumstances ideal germination conditions may arise and these seedlings will soon anchor themselves to the membrane and worse still eventually root through it into the soil beneath.
Dealing with this kind of scenario, especially once the perennial weeds are well established negates any benefit derived from the use of the geotextile with the most likely solution being to grub everything out and replant afresh.
A solution that appears to work best is to plant quite densely and to omit the membrane, using a decently thick layer of composted bark instead. Ground smothering plants such as periwinkles are a particularly useful way of filling the gaps in and around other trees and other shrubs. The planting needs to be regularly inspected and any losses made good, the bark needs to be topped up as necessary and any incipient weeds dealt with before they have become established.