Cordyline impact on grass

[Navrig]

My first post.

We have a small lawn which has a south-east outlook so gets plenty of morning and early afternoon sun. Generally it is quite lush and grows well.

We have a couple of trees within the lawn. One is a maple and has no noticeable affect on the grass. The grass grows well underneath the canopy including right up to the base of the trunk.

The other is a cordyline about 3m tall and with a significant list. The area of lawn directly under the cordyline "canopy" is completely bare. I don't think it parched because when it rains the cordyline catches the rain and then it simply drops vertically on the grass below. I have reseeded that area several times and despite some signs of grass growth it quickly stops growing and it reverts to bare soil.

I wonder if the rain is picking up some sort of exuded chemical which then poisons the grass below. The attached photo shows the issue.

Anyone have any thoughts?

 

[Oliver Buckle]

That's a strange one, on line people talk about very large trees (8 meters) and vigorous root systems giving trouble, but that doesn't look like either of them, and nobody even suggests anything that might kill the grass coming off the tree. You say it catches the rain which drips on the grass below, could the rain be running along the leaves, dripping on the grass, and leaving a dry spot?

 

[Meadowlark]

Welcome @Navrig . The area that is bare is very likely caused by the leaning Cordyline that casts an intense shadow. Most grass requires full direct sun. I don't know if St. Augustine grass is available to you, but it will tolerate some shade.

 

[Navrig]

Welcome @Navrig . The area that is bare is very likely caused by the leaning Cordyline that casts an intense shadow. Most grass requires full direct sun. I don't know if St. Augustine grass is available to you, but it will tolerate some shade.

It definitely not shade. We are northern hemisphere and that patch is south-south-east of the tree.

 

[Navrig]

That's a strange one, on line people talk about very large trees (8 meters) and vigorous root systems giving trouble, but that doesn't look like either of them, and nobody even suggests anything that might kill the grass coming off the tree. You say it catches the rain which drips on the grass below, could the rain be running along the leaves, dripping on the grass, and leaving a dry spot?

Initially I thought that was the case but there are so many leaves directly above the patch that I am pretty sure there is an fairly even distribution of rain from the leaves.

This tree is 3m at the most. It's difficult to tell which way the roots travel but given the extent of the list I suspect a lot of the roots are on the opposite side of the patch otherwise the tree would fall. It's stayed up longer than I expected to be honest.

 

[Sheal]

Have you investigated what's underneath that patch? Possibly rubble, sand etc. that isn't elsewhere on the lawn.

 

[oneeye]

That could be an old dump spot from the construction. You need to dig that area out and replace with some quailty topsoil and replant seed when its seed planting time. If you can get a truck of load of composted manure or quality topsoil it would help the whole lawn. The whole lawn looks like it needs help.

 

[Navrig]

That patch sustained grass before the Cordyline was planted so it's not rubble etc.

I am about to oversow clover and wildflowers. I just wondered why that patch happens.

 

[Oliver Buckle]

That patch sustained grass before the Cordyline was planted so it's not rubble etc.

I am about to oversow clover and wildflowers. I just wondered why that patch happens.

I think the first sentence answers the question in the last sentence, it's something to do with the tree. Is it a denser shade than the maple? Is the ground noticeably drier if you turn a little bit there and a bit elsewhere? They are the most obvious reasons.

 

[Navrig]

I have never doubted that it's caused by the tree, I think thats obvious from my original post.. I am trying to workout what the tree "does" to cause it.

 

[cpp gardener]

It might be that the ‘concentrated’ water dripping in the same spot has compacted the soil there. Sort of ‘pounded’ the grass to death. Or washed nutrients out due to leaching.

 

[Oliver Buckle]

Can you access a moisture meter? It really seems the most likely thing, grass doesn't give up because of a bit of shade usually.

 

[Navrig]

It might be that the ‘concentrated’ water dripping in the same spot has compacted the soil there. Sort of ‘pounded’ the grass to death. Or washed nutrients out due to leaching.

I don't have access to a moisture meter and I know, 100%, this is not a shade issue. The tree NEVER casts shade on that spot.

That spot gets wet whenever it rains however the rain has to pass through the cordyline foliage before getting to the ground. This is why I was asking if the rain water could pick up something from the foliage which might inhibit grass growth.

It might be that the ‘concentrated’ water dripping in the same spot has compacted the soil there. Sort of ‘pounded’ the grass to death. Or washed nutrients out due to leaching.

You might have a point here - the washing of nutrients out perhaps. I'll rake the spot and sow some clover to see if that takes.

 

[oneeye]

The only way to know without guessing is to send a soil sample to the soil lab for testing. When I encountered problems in landscaping, I would send a soil sample to the soil lab at the customer's expense. I have sent many samples, and it always paid off in the end. Without a soil test you are just spinning your wheelbarrows.

Soil and forage testing companies | AHDB

A list of companies that offer soil testing and/or forage analysis.

ahdb.org.uk