I have a very invasive type of moss which spreads inexorably through the
grass in the lower half of my garden. This part of the garden slopes downwards
from the main lawn is not waterlogged but it is shadied by a large oak tree
and some shrubs.
It is also in the lawn on poor soil though I have been able to keep it
down there with liberal doses of ferrous sulphate delivered by watering can.
I really would like to eliminate it on the lawn and preferably elsewhere
though this would appear to me to be really difficult. I recently cleared one
patch of about 8m2 by digging it up! That was hard work.
This moss is very feathery and left to it's own devices stands 1-2.5cm high
and apparently immune to ferrous sulphate. I am interested in identifying
this moss as a first step in finding a better way of getting rid of it.
I hope the first picture is good enough. The second shows how it spreads into
grass killing it. This moss has the characteristics of Japanese knotweed and
I'm worrying about it spreading into my neighbours' gardens.
It looks very much like "Sphagnum moss" to me. It needs cool moist conditions to thrive, and digging it out is only a temporary solution. It will return unless you drain the soil and dry the area out.
Maybe someone more knowledgeable could confirm?
your moss is almost certainly Polytrichastrum formosum (Hedw.) G.L. Sm. (= Polytrichum formosum Hedw.). This is a fairly common woodland species that occurs in drier situations than its larger and similar looking relative P. commune Hedw. The latter is the tallest growing of the European terrestrial mosses sometimes forming hummocks more than 50cm tall. This group of mosses have a rather distinctive appearance - the spiky leaves making them look a bit like miniature yuccas. On the surface of these leaves - which are rather thick and complex in structure for a moss - are aligned closely packed parallel tiers of green photosynthesizing cells. When the plant dries out the leaf margins fold over to an extent to protect these arrays. Various methods are used to ensure water (and essential nutrients) can move up the plant - which is quite robust for a moss. As you've noticed it can develop quite an extensive branching system. All of this group of mosses prefer acid conditions and many will survive in quite toxic conditions on metal mine waste and so will be less susceptible to control methods using iron, copper, etc.
Many people regard any large moss as Sphagnum - this group of mosses has a very distinctive structure with short clustered branches, usually of 2 types which when young form a distinct capitulum - a head of stubby branches at the shoot tip. The leaves are of 2 different types on stems and branches and all have a cell structure largely made up of air spaces.
Given the choice I'd rather have moss than grass - although I appreciate that my tastes and interests aren't necessarily "normal" - there is a good book on Moss Gardening published by Timber Press although I'm not sure if this deals in depth with control.
I doubt it will prove to be very invasive - once it is away from the shade cast by the trees and in denser turf with more competition it should be much less of a problem.
Many thanks for your identification of my invasive moss, Polytrichastrum formosum. A Wikipedia article refers to it having rhizomes by which it spreads vegetatively and this is what it seems to do well. I have seen spores on some of the "better" growths. The best thing I have found to kill(?) it is Scotts Weedol Max but this kills all green material including grass and still takes a few goes to eradicate it. In the rough grass I'm hoping that the couch grass stolons will survive better that the moss's rhizomes!
However, I really want to get rid of it in my lawn. Its very invasive there as well, even on the sunny side! You say it doesn't mind iron and might even like it so perhaps Ferrous Sulphate is not very good for getting rid of it. I wonder if there are any other pointers. I feel sure I used to be able to buy something quite good against this moss but it disappeared from the shops, I think perhaps because it was potentially dangerous to amateurs. Any ideas for anything else?