French garden diary - April 2019
How do your tall grasses grow? Cathy Thompson gives her tips for creating elegant textures using tall grasses
What does the April garden mean to you? If I am not enjoying tulips, daffodils and early-flowering Rosa banksiae ‘Lutea’, I am usually rushing to finish the jobs I did not quite complete in February/March, because it was too wet to walk on borders. And, as early as possible, I have to lift, divide or cut back ornamental grasses.
Grasses generally fall into two groups. The first group are those coming from warmer, Mediterranean climates. They include some of the prettiest, most delicate grasses, often used in public parks displays: feathery little Stipa capillata and S. tenuissimma, or Pennisetum villosum and P. setaceum cultivars in fashionable pinky-purple shades. But the group also includes some pretty tough plants that will do well in most parts of France: Cortaderia (pampas grasses), Stipa gigantea, Arundo donax, Miscanthus, Panicum and the hardier Pennisetums, such as P. alopecuroides.
These do not come into growth until late spring and continue to bulk up through the summer, flowering late in the season. April to early May is the best time to lift, divide and cut back.
If you are not planning on interfering with a mature plant, best to leave them with their top growth intact through the winter, to provide a little protection. Then, in April or May, carefully thin the foliage with your fingers or lightly rake the tufts over just before the fresh growth begins to appear.
Cool season grasses do most of their growing in spring, so have to be cut back sharpish in March or very early April – leave it as long as the warm season types and you risk squaring off the emerging tips of the young foliage. These grasses include the tall feather grass Calamagrostis, Chasmanthium, Deschampsia, little Festuca, Hakonechloa, steely-grey Helictotrichon sempervirens and Molinia.
As our summers become drier, grasses have become the mainstay of my garden during the dog days. They require little or no watering and I try to add one or two new cultivars each year. Since they resent autumn plantings, April’s the season if you want to dip your toe in the water of this satisfying group. My ten ‘must-have’ grasses for the garden:
1. Stipa gigantea or ‘Golden Oats’. The trend for ‘see-through’ plants never goes away. Planted at the front of a border, the foliage makes a tuft no more than about 50cm, but the long stems of oat-like flowers are a perfect foreground for bright Monarda ‘Cambridge Scarlet’.
2. Stipa tenuissima. This smaller oat-grass is altogether more feathery in effect. Since it is small, even in flower (30-40cm), it demands planting in groups. A good partner for small scabious, such as ‘Butterfly Blue’.
3. Miscanthus cultivars. Very tall (to 2m), and often with showier than usual grass foliage for bold displays. Try ‘Morning Light’ and ‘Kleine Silberspinne’.
4. Helictotrichon sempervirens. Determined and very tolerant blue-foliaged oat-grass, to 1m.
5. Molinia cultivars. The low tufts of foliage, shooting to 1.8m in flower, can be very useful in a winter garden.
6. Festuca amethystina. This low-growing fescue (up to 40cm) is amongst the earliest flowering grasses, perfect for its grey foliage and haze of purplish stems.
7. Deschampsia cespitosa. Easy to raise from seed, so you can create a prairie planting for next to nothing. A cloud of flowering stems rising as high as a metre in late summer.
8. Pennisetum alopecuroides ‘Hameln’. I adore the large, showy bottle-brush flowers of the pennisetums, but this is the only one that is perennial in my cold garden (to 1.5m in flower).
9. Panicum virgatum ‘Heavy Metal’. Impressive height (to 1.5m) and very stiff but airy flower stems, to contrast with gentler grasses such as Deschampsia.
10. Calamagrostis ‘England’ or ‘Karl Foerster’. Very upright contrasts (to 1.5m plus, in flower) for a grass planting. ‘England’ has yellow-variegated foliage.
OVER TO YOU
What are your personal likes and dislikes among annual flowers? Email me at: firstname.lastname@example.org