Rhododendron Muncaster Trumpet

May flowers to plant: best flowers for May

As the days and soil gets warmer, Keith’s choice include colour, from a bright-orange lily to a crimson rose, offset by the delicacy of a soft-pink viburnum. Words Keith Wiley, photographs Jason Ingram

April sees spring swing into bloom. Here’s plantsman Keith Wiley‘s choices of the best flowers to plant this month. For Keith’s monthly column, subscribe to Gardens Illustrated magazine. 

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Wildside Nursery Garden
© Jason Ingram

1

Rhododendron ‘Muncaster Trumpet’

Rhododendron Muncaster Trumpet
© Jason Ingram

Although spoilt for choice in May for rhododendrons, I have always had a soft spot for those cultivars sporting hanging bells, as in ‘Muncaster Trumpet’. Many of this type are hybrids of Rhododendron cinnabarinum and have relatively small, oval, blue-green leaves and a stiff upright growth habit. They need and merit a sheltered, woodland setting with good air movement, as they are not the easiest of plants to grow well, but when covered in flowers they rank among the most beautiful we can grow outside. Height 2-3m. Origin Garden origin (species east Himalaya, Nepal, Tibet). Conditions Neutral or acidic soil; part shade. Hardiness RHS H4, USDA 5a-8b. Season of interest Spring.

2

Acer palmatum ‘Matsukaze’

Acer palmatum 'Matsukaze'
© Jason Ingram

This Japanese maple is truly multi-seasonal in its attributes. Its leaves emerge in spring a rich, bronze to red colour that very gradually fades to green by mid-summer before exiting in the autumn in glorious scarlet before they fall. These colour changes are by their very nature short-lived, so the display of crimson-red seedheads, which appear soon after leaf emergence and can last for months, if frosts haven’t spoilt the flowers, is eye-catching and very welcome. It is very similar to Acer palmatum ‘Chitose-yama’. Height 2-3m (3-4m wide). Origin Garden origin (species Japan). Conditions Well-drained, good soil; full sun to part shade. Hardiness RHS H5, USDA 5a-9b. Season of interest Year round; spring to summer for seeds.

 

3

Roscoea ‘Ice Maiden’

Roscoea 'Ice Maiden'
© Jason Ingram

Roscoeas, members of the ginger family, are hardy, tuberous-rooted perennials that can be in flower from April right through to September. Pure white ones, such as this, are fairly thin on the ground at any time of the year. This cultivar, one of the earliest of the roscoeas to flower each year, is a seedling selection by Irish plantsman, Gary Dunlop that has pristine pure-white Roscoea humeana f. alba in its DNA. Unlike the straight species, it is easy to grow, and seems to have very few foibles. The pale yellow in the flower centre is extremely distinctive. Height 30-45cm. Origin Garden origin (species China). Conditions Well-drained, humus-rich soil; full sun to part shade. Hardiness RHS H4, USDA 8a-10b. Season of interest Spring.


4

Viburnum plicatum f. plicatum ‘Rosace’

Viburnum plicatum 'Rosace'
© Jason Ingram

I remember the day I first saw this plant in full flower in a garden as clearly as if it were yesterday. The plant I saw was about 2m high with crinkled coppery coloured leaves, and sporting all along the top of its layered branches, rounded heads of soft-pink flowers. I thought it was one of the most beautiful flowering shrubs I had ever seen. Having grown it ever since, familiarity has not dimmed my enthusiasm. After flowering the leaves turn green and best colour is achieved by growing in nearly full sun. Height 2m. Origin Garden origin (species Japan). Conditions Good, humus-rich soil; full sun to light shade. Hardiness RHS H6, USDA 5a-8b. Season of interest Early summer.

 

5

Lilium pomponium

Lilium pomponium
© Jason Ingram

A small lily with a difference that relishes a really warm, sunny spot. Although it originally comes from the limestone mountain ranges of the southern Maritime Alps,
in cultivation it does not demand a limey soil. In the garden, as in the wild, it usually produces only two or three tightly curled, deep orange-red Turk’s cap flowers. I grow it in a very stony soil, protected from our high rainfall, where in a good year, each stem can produce upwards of 15 flowers. It can be short-lived, but it is easily raised from seed, usually flowering by the third year. Height 30-60cm. Origin Southern France, Italy. Conditions Well-drained, soil; full sun. Hardiness RHS H4, USDA 4a-8b. Season of interest Early summer.

6

Athyrium ‘Ghost’

Athyrium Ghost
© Jason Ingram

I have been growing the Japanese painted lady fern, Athyrium niponicum var. pictum, all my gardening life, but have found that it’s low stature and running habit was not sufficiently robust to withstand the general hurly-burly of life in the open garden. So, discovering a silver-leaved fern that was taller with the classic vase shape of wild ferns and robust to boot, was a revelation. It has not disappointed and even though I have now grown many other silver-leaved ferns, this one still remains top of my pile for garden worthiness. AGM*. Height 60cm. Origin Garden origin (species Japan). Conditions Moist, well-drained soil; shade. Hardiness RHS H5, USDA 4a-8b. Season of interest Spring and summer.

 

7

Euphorbia ‘Blue Haze’

Euphorbia 'Blue Haze'
© Jason Ingram

This compact spurge, bred by Robin White of Blackthorn Nursery, is a wonderful plant for a sunny, well-drained (even poor and stony) soil, looking especially good where the ground is surfaced with gravel or stones. With narrow, blue-grey leaves it is smothered with yellow-green flowerheads in early summer, making a wonderful foil
for other rounded shrublets, such as helianthemums. After flowering, cut it back to keep the plant compact and improve flowering the following year, but wear gloves as the sap can be harmful. Height 30cm. Origin Garden origin (Euphorbia seguieriana subsp. niciciana x Euphorbia nicaeensis). Conditions Well-drained soil; full sun. Hardiness RHS H5, USDA 6a-10b. Season of interest Year long; early summer for flowers.

 

8

Rosa ‘De Resht’

Rosa Rose 'De Resht'
© Jason Ingram

I don’t expect any sympathy from those of you gardening on alkaline soils in drier parts of the country, but roses are generally not good in high rainfall areas. However, this shrub rose, an older cultivar, is an exception to this rule and an utter delight. It flowers all summer long and well into early autumn with highly scented, double flowers. It makes a compact, well-shaped bush with lush foliage, remarkably tolerant of blackspot and seems just as happy in a semi-shaded spot as in full sun. It was also my wife’s favourite rose, and so it has now become my favourite too. AGM. Height 1-1.5m. Origin Garden origin. Conditions Well-drained, soil; full sun. Hardiness RHS H7, USDA 4a-9b. Season of interest All summer.

 

9

Wisteria floribunda f. alba ‘Shiro-noda’

Wisteria floribunda 'Alba'
© Jason Ingram

I love wisterias of all sorts and one at least would definitely make my desert island list of plants. I grow many as free-standing shrubs with one or more short trunks, given a strong support in their early years until they can support themselves. Any wisteria can be grown like this, and then pruned in the normal way to make wonderful specimen plants. Wisteria floribunda cultivars tend to have longer racemes of flowers, and this highly scented cultivar, flowers slightly later than others, and is simply magnificent. AGM. Height Climber to 6m. Origin Japan. Conditions Well-drained soil; full sun to part shade. Hardiness RHS H6, USDA 5a-8b. Season of interest Early summer
for flowers.

 

10

Geranium sanguineum var. striatum

Geranium sanguineum var. striatum
© Jason Ingram
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It is easy to overlook perennials that are almost bomb-proof in their reliability not only to grow but to flower every year. This geranium comes into this category, growing nearly anywhere, immune to pests and diseases, and covering itself for months with intricately veined flowers above gently spreading tidy clumps of attractive foliage. Small and neat enough to consort happily with alpines or bulbs, yet robust enough to be used as an effective groundcover to prevent weed growth, this is a plant that deserves
even more widespread planting. AGM. Height 20cm. Origin UK native. Conditions Well-drained soil; full sun to part shade. Hardiness RHS H7, USDA 4a-8b. Season of interest All summer.