Why doesn’t grass grow around my conifer tree?

By | 22/08/2014
Lawn around a conifer tree

It seems that, no matter what is tried, grass just does not seem to grow around the difficult areas underneath and around conifers. So why is this?

Basically, for any plants to survive, it needs access to water, light and nutrients, and the conifers (or ‘Pinophyta‘ species), have evolved fantastic lines of defence to prevent any other plants from growing too near them. It is a very effective mechanism, and bad news for lawn owners with a conifer hedge! Growing a lawn around a conifer tree is very difficult.

Conifer defence mechanism 1: Prevent germination

The very first step in the life cycle of a grass plant is to emerge from a seed, and the conifers are masters at preventing other species from invading their space. The ‘needles’ (actually the leaves of the tree) that are dropped onto the soil actually emit a gas which stops any seed in the vicinity from germinating. This is compounded by the fact that they are evergreen (so the needles are dropped year round) and they take a long time to decompose, staying on the surface for a prolonged period.

If you try to be vigilant and try to rake the needles up, you just stir the gas coming from them, making the problem worse. This is a fantastic advantage from the trees’ point of view, as they don’t even have to try to compete. They just prevent the competition from starting!

Conifer defence mechanism 2: Poison the soil

The needles of a conifer are extremely acidic in nature … usually pH of 3 to 4. This acidity seeps into the soil “locking” in the available nutrients. Very few plants can survive at this very low pH, and so any plants that are lucky enough to germinate and put down a root, instantly find the soil extremely unwelcoming and all but the most acid-loving plants struggle from the outset.

Conifer defence mechanism 3: Remove the moisture

All plants need moisture to survive, and grass is no different. The roots of conifer plants grow extremely densely and very close to the surface of the soil, sucking any moisture out of the soil quickly and efficiently, leaving none left for any hapless plant within its reach. Even in wet weather, if you examine the soil around a conifer it will often feel totally dry. Again, this is very bad news for lawns!

Conifer defence mechanism 4: Remove the light

The process of photosynthesis is the chemical reaction of converting sunlight into starch. It is the way in which all plants make food and grow. Some plants can tolerate a high degree of shade, including some lawn grasses. However, the deeper the shade, the slower the growth, until the shade becomes so deep that the plant does not grow at all. If you have ever walked in a mature pine forest, you will realise just how much light a conifer canopy blocks out and it can be as dark as night in a conifer forest even in high summer. This is the same situation that a tiny grass plant faces underneath a conifer in your garden. With a large portion of the sky literally blocked out, any plant is really up against it, and will only grow slowly, if at all.

Conifer defence mechanism 5: Compact the soil

For a grass plant to grow it needs to have roots. These roots are the mechanism in which water and nutrients are taken up from the soil. If the roots cannot penetrate the soil, the plant cannot grow. It is the same reason why grass does not grow on concrete or paving. Conifers create a dense mat of roots just below the surface of the soil all around the tree, which bind the soil together making it extremely hard and compacted, preventing any other plant from putting down roots.

In summary, conifers are extremely adept at keeping their space in the ground exclusive. They don’t tolerate invaders at all, and that includes the humble grass plant.

Lawn around a conifer bush
The thinning lawn around a conifer bush

So can you grow a lawn around a conifer?

It is an unfortunate situation that can make a lawn look unsightly. A gorgeous green piece of turf with a dead circle at one side. I’ve seen it many times and am regularly quizzed about it. Unfortunately the solution is rather bleak. You can either have the conifer, or the lawn … but rarely both! I have seen some limited success with owners applying good quality compost to the affected area and re-seeding, this gives the grass a good start. This will then need to be repeated periodically to keep the grass going and to keep the soil full of nutrients. However, this will always be an ongoing battle and continual upkeep will be required. Usually, the only option is to give up on growing a lawn around a conifer!

There are some other plants which maybe able to tolerate living close to the inhospitable conifer.

First though, I’d advise putting in lots of holes, incorporating lots of organic matter. Add some slow-release fertiliser and some water-retaining gel to get anything off to a good start.

Alternatives to a lawn around a confier

Some bulbs such as hardy cyclamen should do quite well, as well as some species of box and ferns. Periwinkles, pulmonaria, primroses and sweet violets should also manage in the dry shady conditions. The experts at Gardeners World Magazine say that for ground cover Euonymous fortunei ‘Silver Queen’ should cope well, as will hellebores, ivy, bugle and some small shrubs like bay and osmansthus should all manage.

But to be honest, if weeds can’t even grow in that area, then anything else may only be temporary. For a long term solution, it may be best to just edge it off. Or put down a couple of bags of gravel with some pots. Or more drastically, cut down the conifer, dig out the root ball, re-fill with topsoil and re-seed. Check out the RHS Website for some more tips.

If you need any advice about your lawn, please don’t hesitate to get in touch.

Kris Lord

7 thoughts on “Why doesn’t grass grow around my conifer tree?

  1. radiohertz

    All plants need moisture to survive, and grass is no different. The roots of conifer plants grow extremely densely and very close to the surface of the soil, sucking any moisture out of the soil quickly and efficiently, leaving none left for any hapless plant within its reach. Even in wet weather, if you examine the soil around a conifer it will often feel totally dry. Again, this is very bad news for lawns
    Thanks

    Reply
  2. Sue Dot

    Recently cut down a row of leylandii. Considering using large pots for planting a bamboo, a mahonia, an acer and a buddleia in the space. The leylandii roots are still in the ground and also the soil will be too acid for plants. Thought about grassing the area first, or should I just leave it and put the pots there? Any suggestions would be much appreciated – thank you for your time.

    Reply
    1. Kris Lord Post author

      Hi Sue,
      Yes, you could try grass the area now that the conifers have been cut down. If the roots are still there though you will find that the area will sink as the wood rots away. You will also get a lot of fungi in the area decomposing the wood. There will also not be very much nutrients in the soil so improving it with some organic matter before laying the lawn would be very beneficial.
      Ideally, if you are trying to grass it over I would recommend trying to get the stumps out and improve the soil first though as the grass will do a lot better with the root space and improved soil.
      Thanks for reading.
      Kris

      Reply
  3. Jim Groves

    Hi Kris my newly seeded lawn in May grew about 80% and has been cut ok; the reseeding now done twice under some shading from trees,has not grown at all.
    One tree has very acidic leaves which fall all the time on the grass,is it likely to be the problem? I remember its leaves had not grown much in June but with very dry weather this year,there has been a lot of dropping. thanks Jim Gee

    Reply
    1. Kris Lord Post author

      Dropped leaves maybe the problem, but it is also the lack of light will also be a contributing factor. Ideally, even “shade tolerant” grass needs to see the sky in a direct vertical line overhead to thrive. You will always have trouble growing grass under trees. That’s just the way it is I’m afraid.
      Thanks for reading.
      Kris

      Reply
  4. mary hodges.

    I have had a round conifer plus roots removed from the middle of my lawn,but unfortunately the new laid turf will not grow This has been fed and watered, but it makes no difference,your help would be much appreciated.

    Reply
    1. Kris Lord Post author

      Hi Mary, If the area is not shaded there is probably a problem with the soil. Lift the turf and dig the area over thoroughly, improve with some compost or soil improver, level, water well and the replace the turf and it should do much better.
      Thanks for reading!
      Kris

      Reply

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