Helpful hints for cultivating colourful coreopsis

Coreopsis is one of the most dependable summer-flowering perennials that you can grow in the garden or a container: colourful, cold-hardy and virtually trouble-free, it's sure to become the centre of attention wherever you put it. Here are some helpful tips for cultivating coreopsis.

[Image credit: iStock.com/schnuddel]

Sunny yellow blossoms are the hallmark of native North American coreopsis.

• This is a varied group of plants ranging from the 1.2-metre tall (four-foot) lanceleaf coreopsis (Coreopsis lanceolata), which is usually found in every wildflower meadow, to several compact modern counterparts that stand less than 45 centimetres (18 inches) tall.
• The yellow flowers combine beautifully with soft blues and pinks, but you may need to experiment to find companions that share the same bloom time.
• On the West Coast coreopsis remains green through winter and may bloom in late spring, along with fall-sown larkspur, Shirley poppies and roses.

Where winters are colder and coreopsis holds its new growth until spring, mix them with mid- to late-season bloomers, such as campanula or pastel-flowered yarrow.

• You could also set them against a background of Russian sage.

Some coreopsis cultivars come in neat, garden-sized packages that fit into tighter spaces. Among the compact coreopsis options you'll find:

• C. verticillata 'Moonbeam' (Zone 3) stands 45 centimetres (18 inches) tall. Its airy, threadlike foliage is topped by petite, 2.5 centimetre-wide (one-inch), pale yellow, daisy-shaped flowers.
• C. grandiflora 'Early Sunrise' has yellow semi-double blossoms held on stiff, 40 centimetre-tall (15-inch) stems.
• Shorter still is C. auriculata 'Nana', with 2.5 to five centimetre (one to two inch) yellow-orange flowers topping 30 centimetre-tall (one-foot) plants.
• C. rosea adds pale rose flowers to the spectrum. At 40 centimetres (15 inches) tall, C. rosea requires supplemental watering in hot, dry weather. If grown in favourable conditions, it makes a handsome groundcover.

You likely won't find a tougher, more versatile plant than coreopsis.

• Coreopsis will survive in poor, dry soil, but it produces more flowers if given regular water and a little organic or controlled-release fertilizer each spring.
• Once it's well-established, coreopsis won't perish in a drought.
• If you garden in an area with wet winters, plant it in well-drained soil to prevent root rot.

Reblooming
Deadheading, or removing spent flowers, keeps the plants neat and encourages reblooming.

Pest problems
Insects rarely visit coreopsis.

• The occasional aphid can be knocked off with a spray of water from a hose.
• Remove weeds and garden debris to discourage nesting places for pest insects.

If you encourage coreopsis to grow into small colonies, they will practically take care of themselves.

Dividing plants
To increase your supply or rejuvenate old clumps, divide plants in late summer using a stout knife.

• Locate a tuft of foliage growing outside the mother plant, cut a circle around it to take out a few roots with the surrounding soil, and lift it out of the ground with the knife blade.
• Replant right away so that it will be well-rooted by spring.

Coreopsis is an excellent addition to any garden and grows well with campanula, larkspur, Russian sage, rudbeckia and Shirley poppies. Hardy and vibrant in colour, a garden simply isn't complete unless it has coreopsis growing in it.