"Unravelling grasses, rushes and sedges"

These plant have much to offer but can confuse!
Sunday, 29 May 2022     

Miscanthus sinensis Sarabande in flower

During a recent discussion with gardening friends about ornamental grasses and grass-like plants, I realised I basically didn't have a clue what was an actual botanical 'grass' and what was not, nor what on earth these other 'grass-like' plants actually were classified as! Certainly, they all have linear leaves - offering wonderful textural opportunities for contrast in the garden, and all are wind-pollinated, thus not having flashy, colourful blooms - but there are so many plant families that comprise this fascinating group.

Trying to unravel it all only made me realise how complicated it all is and as I am no botanist, I won't even attempt a proper exposition of the subject. However, I found it interesting to learn a little more about the different groups, as one important thing I discovered is that they like different conditions in the garden so it's useful to be able to distinguish them at least on a very basic level.

True grasses belong to the family Poaceae, and they have long, flat leaves on two sides of rounded stems that have nodes. The stems are hollow between the nodes. Bamboo is probably the largest of the true grasses, where these features are very obvious! In general, grasses prefer to grow in well-drained or even dryish soils in full sun. In our Sydney climate, Miscanthus sinensis cultivars (ht 1-2 m) are some of the best true grasses to use in the garden, providing height, texture and movement as they react to the slightest breeze. They can be a good 'exclamation point' amidst lower-growing plants. The soft plumes of flowers in autumn are an added feature. I am fond of the cultivar 'Variegatus', with its white-and-green striped leaves, lending itself to colour echoes with nearby white blooms. Miscanthus need to be cut to the ground in early winter to allow the new leaves to grow up, and the clump reduced in girth every so often.

Other useful (and smaller) grasses that do well in Sydney include Pennisetum setaceum 'Rubrum' (ht 1-1.5 m), with its rich burgundy leaves and bottle-brush-like flower heads. The ordinary Pennisetum can self-seed but I have never had this issue with 'Rubrum'. I also like quaking grass (Briza media, ht 45 cm), with its quaint flowers like ears of wheat. There are some very attractive Australian native grasses: the tussock grass, Poa labillardieri 'Suggan Buggan' (ht 80 cm), has thin, silvery leaves and pretty panicles of flower spikelets, and forms a pleasing clump. Another that I have admired but am yet to grow is the long-hair plume grass, Dichelachne crinita (ht 1 m), with erect, silky flower heads.

Rushes generally belong to two different plant families: Juncaceae and Restionaceae. Rushes usually like to grow in wet, boggy conditions in sun. Stems have no nodes and are generally cylindrical. They are solid in the case of Junaceae, but can be hollow or solid in Restionaceae family members. The form of rush is usually quite upright. The flat leaves, which are on two sides of the stem like grasses, may be reduced to sheaths at the base of the stems so that the stems are the main feature. The genus Juncus is the most common in the Junaceae family, with many of them having weed potential. The flowers on the inflorescence spikes often have a 'bobbly' form. I have recently acquired the native velvet rush Meeboldina scariosa (ht 50 cm), from the Restionaceae family, which has thin, slightly wavy upright stems and red-brown flowers in spring and summer. I am looking forward to watching its progress.

Sedges belong to the Cyperaceae family (which also, confusingly, contains some rush-like plants). Generally speaking, sedges are recognised by their triangular, solid stems that have no nodes. The leaves, which are arranged spirally on three sides of the stem, are flat and have a ridge down the middle. The inflorescence is in the form of a spikelet, but these don't appear to be as showy as those of the true grasses. Sedges prefer part-shade conditions but seem to be able to handle a range of soils, from moist to dryer - though on the whole, sufficient moisture will produce a better plant. standout sedges The genus Carex contains most of the cultivated sedges and has over 2,000 species. I have only recently become aware of the array of these that grow well in Sydney, though many of my gardening friends have been growing them for years! They are generally quite low-growing plants (ht 30-60 cm) and have a diversity of leaf widths, colours and forms. They have a lovely arching shape, and are excellent as a feature plant, massed as a groudcover, or used as an edging along a path. Some of the delightful Carex that I am now growing include golden Carex oshimensis 'Everillo' (ht 45 cm); green and creamy-yellow striped Carex oshimensis 'Evergold' (ht 30 cm); and the ethereal-looking, silvery-green Carex albula 'Frosty Curls' (ht to 60 cm). There are a number of native Carex species, and I have discovered that 'old man's whiskers' (Caustis flexuosa) - familiar to me from childhood rambles in the bush near my family home - is a sedge, with its intriguing curly stems!

As well as these plant families, there are a number of others with grass-like members! The Asparagaceae family encompasses Liriope, Lomandra and Ophiopogon, all tough doers with many different and interesting exemplars, which will cope with dry shade; the Acoraceae family has but a single genus: Acorus, an excellent small plant for sun or shade; the Xanthorrhoeaceae family includes Dianella, Bulbine and the wonderful Australian native grass tree (Xanthorrhoea australis).

I think that all of these grasses and grass-like plants need to have space around them to allow them to show their form. I have learned the hard way that allowing other plants to crowd them does them a disservice. In many cases, growing them in a pot is an ideal solution to this problem.

 Reader Comments

1/3  Kerrie - 2104 (Zone:10 - Warm Temperate) Monday, 30 May 2022

Well i did not know Leonotis ( Lion's Tail) was a grass! I have the orange one. Sorry that is confusing in the photo - the shrubby Leonitis was growing with the grassy Miscanthus! Deirdre

2/3  Margaret - 2122 (Zone:10 - Warm Temperate) Monday, 30 May 2022

As you know I am not a grass fan, although I must admit that some, not the dried brown ones, can be attractive if planted in the right position. May be persuaded yet! Hope that you might find something appealing! I do think the Carex are very attractive and not too big. Deirdre

3/3  Pamela - 2158 (Zone:10 - Warm Temperate) Monday, 30 May 2022

Fabulous blog! I LOVE grasses and find them invaluable when planning any border. I grow many Miscanthus, love the variegated Cabernet and Transmorrisonensis is fantastic in a pot backlit by the late afternoon sun. Carex Feather Falls a plant I repeat, the perfect well behaved plant along with the golden Carex. There was a native grass growing in my naturalistic garden area, highly invasive but I keep it there as too hard to remove and it fills a big space. I adore the movement these plants provide. Thanks, Pamela. I do think grasses and grass-like plants really add to a garden. I will look for Feather Falls as I don't know that one. Deirdre

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