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Knoll Gardens


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Grasses for sunbaked and dry

There are so many grasses that are very happy in sunny open conditions in average to dry soils, but there are also those that revel in hot and dry conditions and that really do give of their best by way of foliage colour or flower when conditions are driest. They can thrive when other less robust plants would simply wither away, and it is this happy combination of utility and beauty that makes this group of grasses so valuable to us in our gardens.

Take for example the true beach grass Leymus arenarius. As you can see from the picture above it thrives on sand dunes which are probably amongst the most inhospitable of places to choose to grow! Not only does the sand have virtually no nutrient, it dries out very quickly, and it is also constantly on the move as the individual sand grains are blown around by the wind. The almost constant wind has an immense drying effect on leaves and can also be heavily salt laden which of itself can be enough to kill most garden plants. Yet the leymus not only survives it thrives; so it should be little wonder that it can cope with what we consider to be dry and drought conditions in our gardens as can be seen below from its use in the renowned Gravel Garden at Beth Chattos in the frequently dry county of Essex.

‘Blue’ foliage in fact can be a good indicator of a plants ability to survive in dry and drought prone conditions. Take for example the ever popular blue fescues, mostly forms of Festuca glauca, which do so well in our gardens whether in the ground or in containers. They have narrow foliage on tidy mounds to give an overall spiky appearance and are at their very best in full sun and droughty conditions.

Festuca Intense Blue (above) is a relatively recent form which, as its name might suggest, has really good coloured foliage that only intensifies with the onset of very dry conditions. Festuca Elijah Blue (below) is a good well established favourite that continues to perform well.

Poa labillardierei (Poa lab to its friends!), could be regarded as a much bigger version of a festuca with a wonderful gently cascading habit that creates a light and airy effect (see below). Possibly a more silvery blue foliage, but again its colour intensifying with heat and dry. This is one of my (many) favourites and I love to find another opportunity to use it in the garden.

Helictotricon sempervirens (below), is not as often seen as it might be as it can suffer from rust if not happy in its position but when well suited they make rather fantastic mounds of spiky foliage. It tends to flower rather haphazardly and while beautiful when they do occur the lack of flower is hardly an issue with such good shape and foliage on offer.

Another grass with a fairly unpronounceable name is Bothriochloa bladhi (below), but it more than makes up for its name with the show stopping displays of pinky red flowers that simply cover the plant when in full flower during the summer months. I have it growing happily in the bottom part of the Bark Circle borders at Knoll where it has survived several wet winters seemingly without even noticing them. I was not to sure about this grass liking our UK gardens as it demands full sun and well drained soils to prosper but they have been growing successfully for some years now but even so I would probably not use this in colder areas however well drained the soil was.

The fountain grasses, or Pennisetums, are past masters at coping with sunshine and drought and indeed actually require these dry conditions to give of their best. Not grown for their foliage it is the ‘fountain’ of flowers that suddenly explode from the plant during high summer that make them so special. We have looked at some fountain grasses in an earlier blog but I really must mention a few here as they are so fabulous at coping with the driest of conditions in full sun.


They are a perfect Gravel Garden Plant and I have for example groups of Pennisetum Fairy Tails (above) which is a real favourite of mine, and our newly released Pennisetum Dark Desire (below), weaving in and out of other dry loving perennials such as Salvia CaradonnaVerbena bonariensis and even Persicaria Fat Domino in my own Gravel Garden.

Two other grasses I grow in the Gravel Garden are Jarava (Stipa) ichu and Sesleria caerulea. The Jarava is reminiscent of Nassella (Stipa) tenuissima with its mounds of quick growing very fine green foliage, but any resemblance stops when it comes to the flowers. The Jarava has quite wonderful long white flowers that wave in the slightest breeze and really are amazingly attactive. I first really noticed this plant when I saw it in full flower at RBG Kew (see below) and was immediately entranced by its airy elegance. I also grow it in a pot where it seems equally happy.

The Sesleria caerulea is a rather different plant, being a slow growing effectively evergreen grass whos chief claim to fame is its quietly attractive bicoloured leaves produced on tidy rounded mounds. The overall effect is of blue grey and while not having quite the colour intensity of the popular blue festucas it more than makes up for this in my opinion by being very robust and long lived, needing virtually no attention save for a quick annual tidy in spring. I have a lovely informal group of them beside a seat in the Gravel Garden planted just far enough apart to be able to see their individual shape.