How to get rid of weeds under pebbles?

[MYC]

My small front area with pebbles for at least 10 years no problem until lately.  This area has sun from mid day. Lately I notice green "fungus'?? creeping between and under pebbles.   Why and how to fix? Should I spray like weed spray and fill up more new pebbles?

 

[MYC]

Thanks Eric.  Yes, this part (not the pebble part) is outside the garage window where very little sun but mostly light morning sun.   The big while Arum lily and New Guinea Impatient keep multiplying spreading to this area, even how many time we tried to dig them up.   Now the tiny weeds, looks like what you see in the swamp.   My plan is to remove everything there, then put some perlite and new soil, and plant low maintenance plants that survive that area.  I heard that Hydrangea could be difficult too.  Unless I just let the New Guinea Impatient continue to spread to that area?

[mich1972]

@MYC  Looks like Lichen which is a type of fungal / plant microorganisms. It’s thriving because the area must be constantly damp. You will also find lichens on old rotting timber and deadwood. I personally would not destroy it. People use lichen / moss for their bonsai planters ( as a ground cover ) in terrariums as well. 
Why not carefully scrape it out, place in some takeaway containers and give them to people who will enjoy them. Just a thought. It will always pop up if there’s plenty of moisture in the soil . 

[EricL]

Hi @MYC 

I leave the choice up to you, the good part of the New Guinea Impatient is that it has shown you that it is capable of growing in the soil that's currently there. That's one less thing to modify in that area, aside from removing the weeds. 

I am in total agreement with @mich1972's proposal of propagating the lichen and moss to those who need it. It's not every day that you get a natural source that continually re-news itself. 

Eric

[robchin]

Just following up on this one. 

Do be careful using a path weeder on this sort of thing. What you have here is Liverwort, like a moss. Likely not coming from underneath the gravel but coming in from the top. If you use a path weeder you won't be able to plant back into that bed for 12 months at least - which is fine if that's what you want but not otherwise. A simple contact herbicide will do the job - like this one: Yates 1L Ready To Use Nature's Way Organic Weed Killer Spray - Bunnings Australia

You often find weeds on the edges of pathways because the soil and other muck from the path drains into that area and provides an ideal bed for germination. 

Same for the area in with the second photo. 

Liverworts/Mosses and the types of weeds shown in that photo do have very short life-cycles so will go to seed very quickly and germinate before you know it. You have to be diligent and persistent with these sorts of things. 

Always remember that weed mat will only help you stop weeds that are coming from below - these ones are coming from the top - so may help but certainly won't solve the problem. 

A final note - every time you disturb the soil - you will be promoting weed growth. Turning the soil exposes it to light which actually triggers weed seed germination. 

Keeping weeds down is a mult-pronged approach. 

Good luck.