Lighter patches

I have several circular areas in my lawn where the grass is a much lighter shade of green and grows shorter than the rest. See areas on pic.

Any ideas? I am guessing it is a different type of grass, or maybe the same grass reacting to something under the surface (I have lots of tree roots)?

In the first week of September I raked, overseeded (50% Rye, 30% Red Fescue, 20% Creeping Fescue mix) and top-dressed, and you can see the new seed is growing wonderfully. But the problem patches remain.

Should I dig them out in the spring and seed perhaps?

 

It could be the good old annual meadow grass. Tends to form patches like that and is lighter and less growth now.
You can deter this grass by controlling the PH level but your other grass types are in the same ball park.
Could you post a closer picture of the areas which would be helpful.
I’m a little surprised if you seeded evenly that the patches are so visible.

 

Thanks for the reply. PH is quite high at 7-8.

I seeded very evenly - measured out 35 g per sqm as per the instructions and made a metre square quadrat out of canes. Only problem is I didn't read the seed instructions PROPERLY! It was 35 g for new lawn, 20 for overseeding. So, I over applied the seed.

I didn't scarify as such, I just used a power rake which certainly ripped out lots of surface thatch. It did leave many areas completely bare but these bits were clearly left fairly intact.

See pics.

 

PS its slower growth than the rest of the lawn is the same all year.

 

That’s not annual meadow grass.
Have you tested the ph level in different areas across the lawn. I know there will be a degree of tolerance as it’s not absolute accurate but 8 in on the top limit. It could be below but it could be above.
Test other areas cleaning the probe head between each reading, good areas and the light patches.
It could also be a number of other reasons as well. If these were bald areas some grass types are lighter in colour. Do these areas match the areas where you had to seed a bald area?

 

I have tested the PH all over. It ranges from 6.5 - 8 across. the right side is the lowest PH (which is odd because that is where most of the moss grows). The left side is the highest. The left side gets the most sun, the rest is predominantly shaded and damp.

The PH of the light areas is the same as the good grass surrounding them.

The newly seeded bald areas are a much deeper green so it looks like the overseeding had no effect on these light green areas.

Last week I fertilised with a "pre-seeder" fertiliser to help the roots of the new growth over the winter.

 

Would you say the light patches show the grass drooping, almost limp to the other parts of the lawn?

 

Interesting question! Yes, they do. I have noticed before that they seem to show the dew more and I think that is because the blades of grass are more horizontal than vertical.

 

That’s great thanks. You applied a pre fertiliser, any others applied before hand?
Sometimes grass can go limp due to excessive nutrients but also circles in grass can be what called patch diseases or known as frog eyes. Would you say the center has a greener look or is it an even pale look?
Do you notice if the leaf in these areas has any sign of browning or patches ?

 

They are uniform light green, no difference in center.

Moved in here a year ago in July. At that point lawn was brown from drought. Came back after watering and these appeared.

This spring I did iron sulphate and later Mo Bactor. In the summer I did a general summer fertiliser.

In late August I did iron sulphate and last week I applied the pre-seed fertiliser.

 

Hard to say without being there to be honest Tim. I would see how it develops but normally circles or patches indicate a disease of some type but sometimes it can be hard to diagnose what it is.
It could be that the ph levels have weakened the grass and that’s allowed a disease to pop in or it could just be those particular areas are affected by something else maybe under the soil but I’m going to go for a disease.It’s not uncommon for turf to suffer from diseases and most of them are short lived but at the moment I would simply monitor the turf and see what develops.

 

Thank you so much for your wisdom as always.

The large tree roots that run under the lawn grow giant honey fungus through the lawn in the winter (foot high, two feet across each "mushroom"). I will see if that matches the light grass areas.