An extended flowering season, luminous colours and robust stems all contribute to outstanding displays, says Kevin Line.

C. tripteris - image: Floramedia
C. tripteris - image: Floramedia

For long seasonal flowering displays of bright luminous colour, coreopsis is a real winner. It flowers consistently from May to October and tolerates a wide range of soils and particularly drought conditions.

Coreopsis is a flowering subject I have grown from seed for the past five seasons, simply because it extends the season of flowering with robust stems and bright-yellow flowers at a time when other subjects may be flagging.

My own plant trials have seen coreopsis produce outstanding displays with the vigorous daisy-like flowers of scentless mayweed — a striking combination. Coreopsis will just keep flowering until the first hard frost knocks it back.

In the classic book The English Flower Garden of 1883, William Robinson describes the annuals as the showiest summer flowers making a fine display in spring from seeds sown in September, with an almost continuous bloom to be had from July to October sowing successively in early March until the Middle of June in ordinary garden soil. That of a moist description being preferable for the spring sowings — an invaluable old gardening reference.

Coreopsis, commonly known as tickseed, are members of the Asteraceae family comprising about 114 species of annual and short-lived perennials that are native to north and south America. The genus is very closely related to the summer annual Bidens. Horticultural research suggests this close relationship means they should be included together.

Coreopsis prefer full sun and good drainage, but if moisture is consistent they will step up their flowering performance. Deadheading increases the length of flowering quality up to first frosts. Double and semi-double cultivars can look untidy and faded late in the season. Deadheading will benefit this group and tidy up displays. Perennial forms pruned to ground level prior to frosts encourage new growth to overwinter.

Most species of coreopsis produce flower heads borne on single stems. These form a centrally positioned disc that is encompassed by yellow florets, although occasionally the florets can be white, pink, mahogany or red. Some forms produce a feathered effect. Most of the genus forms a root system that is fibrous. Some species increase from the formation of rhizomes.

The group of C. tinctoria ring the changes from yellow flowers with their red mahogany blotches within the basal area of petals of some of the cultivars. A good number of these need to be propagated from cuttings because growing from seed can produce variable results. Species and hybrids have a short shelf life. Dividing plants every other season can be beneficial in helping to maintain vigour.

The tinctoria group includes ‘Mahogany Midget’, an attractive dwarf plant that reaches 25cm and produces masses of bright-red blooms flowering until the first frosts. C. tinctoria ‘Radiata Tigrina’ is one of the most attractive cultivars. It forms finely cut foliage and flowers until early autumn with vivid yellow flowers. The petals have a sprinkling touch of red for outstanding displays. The plant grows to 30cm and is an ideal bedding variety to add colour and structure to any border.

I am growing C. × hybrida ‘Incredible Tall Mix’ this season. Intensive breeding has produced this variety, which is ideal in the back of the border. At 1.2m it is fast-growing, producing a mix of bicolours — dark red with cream or yellow.

What the specialists say

Brian Ellis, Avondale Nursery, Bagington, Coventry

"Three coreopsis as a reliable long-lived perennial are C. verticillata ‘Grandiflora’, C. verticillata ‘Zagreb’ and C. verticillata ‘Moonbeam’. ‘Grandiflora’ and ‘Zagreb’ have an Award of Garden Merit.

"C. grandiflora ‘Sunray’ and ‘Sunburst’ are well-known, but for me and my customers they have been short-lived. The same goes for C. lanceolata coloured varieties such as ‘Limerock Ruby’, ‘Limerock Passion’, ‘Mango Punch’ and C. rosea ‘American Dream’. All of these are very tempting but seem to be more fussy about conditions."

In practice

Richard Hopkins, Applegarth Nursery, Chipping Norton, Oxfordshire

"There is renewed interest in coreopsis. This year we are growing more varieties. Coreopsis are attractive as they flower profusely over a very long period. The added characteristic is the appeal to bees and butterflies.

"C. verticillata ‘Moonbeam’ was the American Perennial Plant Association’s perennial of the year in 1992 and is still well worth growing. C. ‘Full Moon’ (Big Bang Series) is a similar primrose yellow but has much bigger flowers and sold well. C. ‘Jethro Tull’ was another success.

"This year we are trying C. rosea ‘Heaven’s Gate’, a more compact form with dark-centred pink flowers, and C. verticillata ‘Golden Chain’, a thread leaf type with rich yellow flowers. We have tried some of the more unusual darker and richer flowering varieties, but have been less impressed."

Species and varieties

C. ‘Calypso’ syn. C. grandiflora comprises golden-to-yellow single flowers with basal sections that show a touch of mahogany colour. Stems are bare in the upper sections. Flowers bloom in June and July.

Deadheading will encourage another flush of flowers. Narrow and unlobed leaves are a variegated creamy yellow. Height: 35cm.

C. ‘Crème Brulee’ forms a consistent spreading clump-like growth habit. Striking in appearance, it has leaves with three finger-like lobes 5-8mm wide. These are arranged in opposite pairs that resemble a cluster of leaves at each joint. Sulphur-yellow daisies are a profusion from June to August. Height: 40cm.

C. grandiflora, the large-flowered tickseed, is a short-lived plant that is upright in habit. Undivided leaves split into narrow lobes further up the stem. Yellow flowers are 4-6cm across, comprising about eight petals. Each has three-to-five lobes at the tip that appear from June to September. Height: 30cm-1m.
C. grandiflora ‘Sunray’ (Sonnenstrahl) is a short-lived cultivar that is raised from seed. It produces double golden-to-yellow flowers from June until September. Height: 50cm.

C. lanceolata, the lance-leaved tickseed, is short-lived and comprises lance-shaped leaves that are in the main undivided, occasionally forming one or two pairs of lobes. The upper section of the flower stem is bare of leaves. Yellow flowers, 4-7cm across, are borne from June to September. Height: 20-70cm.

C. ‘Limerock Ruby’ (PBR) has ruby-to-red flowers that are rich in colour. The blooms are a showy profusion from July to September. Compact plants have a branching habit with dark-green leaves, each comprising three thread-like radiating lobes. Height: 40cm.

C. rosea, pink tickseed, spreads from rhizomes. The pink 2.5cm daisy flowers are borne from June to August above thread-like dark-green leaves that comprise up to three lobes. Height: 30-60cm.

C. tripteris, the tall tickseed, is a tall and outstanding upright plant. The flower colour can be described as lemon-yellow surrounding a chocolate-coloured centre point. The flowers are borne from July
until September and the stems are branched at the uppermost sections. Height: 2m.

C. verticillata ‘Moonbeam’ is a very showy and prolific plant, bearing sulphur-yellow flowers some 4cm across. The foliage is almost overcome from the flowering process. In 1992 the plant was chosen as the Perennial Plant Association’s perennial of the year.

Thank you to Floramedia, which supplied the images for this articale from its photo library

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