Black stains on concerete next to Tiger Grass

Question From: 
Bruce Robertson in  Twin Waters,  Twin Waters QLD

 

Nature of problem: 
I have black stains appearing on concerete and paver surrounds of a garden containing Tiger Grass. Please advise what it may be, and how di I stop the stain.

 

Type of Plant (if known): 
Tiger Grass

 

Symptoms of Plant Illness (please try NOT to diagnose your problems yourself): 
Plant appears healthy

 

Soil Type (e.g. sandy, clay or loam) OR Potting Mix Type: 
Sandy, raised mulched bed

 

How often do you water the plant:
Every three days or so

 

How many hours of sunlight does the plant get each day:
Full sun all day

 

What type of plant is it:
Tiger Grass

 

How long since you planted it:
Approx 2 years

 

Have you fertilised? If so, with what and when:
Rooster booster, about 6 months ago

 

Is the plant indoors or outdoors: 
Outdoors

 

What other treatments have you given the plant: 
Trim, mulch trimmings and put this back onto garden

Upload photo if available: 

Other Comments: 
Have tried removing stain with high pressure water without success.

 

Answer: Hi Bruce,  I’m not sure – maybe a photo or two might help. There are dozens of causes for this problem.  Don