Why doesn’t grass grow around my 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.

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