Dianthus Plants: How To Grow Dianthus

Dianthus plants are also known as Carnations, Sweet William and Pinks, and are often a staple in flower gardens. The family of plants are characterized by the spicy fragrance of their pretty blooms, often compared to cinnamon and cloves.

Quick Facts about Dianthus:

• Botanical name - Dianthus
• Height - 6-36 in. (15-91 cm)
• Spread - 6-24 in. (15-61 cm)
• Sun exposure - Full Sun, Part Sun
• Soil requirements - Neutral
• Hardiness zones - USDA Zones 4-8
• When to plant - Spring, Fall

Types of Dianthus

There are hundreds of species within the Dianthus genus. Plants like sweet William and pinks are usually between 6 and 18 inches (15-46 cm) tall. Dianthus flowers are most often in pink, salmon, red and white hues. The foliage is slender and sparsely spread on thick stems. 

While perennial dianthuses are known now for their longevity in the garden, in the past Dianthus had a shorter blooming season. But in 1971, a breeder learned to grow forms that did not set seed, and dianthus now enjoys a more prolonged bloom period. Dianthus plants may be found as a hardy annual, biennial or perennial, and they’re most often used in borders or potted displays

While similar in appearance and flowers, different species of dianthus have varied growth habits and requirements. A familiar dianthus flower, the carnation, produces larger full blooms that are often used in cut flower arrangements. Other smaller types, like pinks and sweet William, are a great fit for ornamental spaces. Learning more about the dianthus plant and its care can be helpful in choosing the best types for your growing space. Below, we will explore how to grow the most common types in greater detail.

How & When to Plant Dianthus

Traditionally, dianthuses are planted in early spring, but not always. Spring-planted dianthus, particularly carnations, can be sown indoors to get an early start to the growing season. Seedlings can then be moved into the garden after a brief hardening off period. Wait until the danger of frost has passed when planting dianthus and place the seedlings at the same level they were growing in the pots, with 12 to 18 inches (30-46 cm) between the plants. Do not mulch around them. Be sure to water them only at the base of the plant to keep the foliage dry and prevent mildew spotting.

Some gardeners begin planting dianthus early in the fall. Many varieties will bloom from May to October, and prolonged periods of cool weather in the fall promote a long period of root development before winter.

Dianthus Care

Dianthus is relatively easy to maintain under its ideal sunlight, soil and water growing conditions. Once they’re established, perennial varieties are known to thrive with only minimal maintenance. Like most flowers, dianthus appreciates routine weeding, deadheading, and pruning. This will help to keep the plants looking their best, as well as aid in preparing the plants for their winter dormancy.

Soil & Fertilizer Requirements

Dianthus grows best in rich, neutral soil on the alkaline side, the best pH range being 5.8 to 6.2. While the plants perform well in rich soil, most dianthuses are able to adapt to a wide range of soil conditions, including those with high amounts of clay or sand. Routine applications of fertilizer are not required. However, they may enjoy annual applications of a well-balanced feed in early spring, which will promote new growth and enhance flowering.

Water & Light Requirements

Dianthus plants appreciate consistent moisture throughout the growing season. Most experts indicate that approximately 1 inch (2.5 cm) of water per week should be sufficient for maintaining the health of the plants. Supplemental irrigation may be required in regions that are especially hot or experience prolonged periods without rainfall.

On the other hand, excess water can be problematic for the plant, often leading to yellowing or the development of root or crown rot. Plants should receive at least six hours of sun throughout the day, though afternoon shade can be beneficial.

Dianthus thrives in full sun, partial shade or in a spot where it will receive at least 6 hours of sunlight each day.

How to Deadhead Dianthus

Before deadheading, or removing spent flowers, it’s best to wait until the flower heads have started to wilt and drop their petals. Deadheading can promote repeat blooms, but will also prevent the production of seeds. To remove old flowers, make certain to clip just beneath the flower head, back to the nearest set of healthy leaves.

How to Propagate Dianthus

Though annual dianthus varieties are most commonly propagated by seed, perennial types are more commonly produced by cuttings. To take a dianthus cutting, simply remove a small segment of the plant's soft stem. The lower leaves, or anything that will be below the soil line, should then be removed. 

Optionally, new stem cuttings can be dipped into rooting hormone before finally being placed into the propagation medium. As the roots form, plant trays can be placed into a humidity dome. In most instances, successful rooting should occur within 1-2 weeks.

Problems, Pests, & Diseases

Dianthus plants only rarely have problems with common garden diseases or insects. Still, weekly monitoring for damage caused by garden slugs or aphids may be needed. These issues seldom lead to the loss of plants, but may negatively impact the plants’ overall ornamental value. Deer resistant types are ideal if you live in rural areas or areas frequented by browsing native wildlife.

Dianthus Flower Varieties

There is a dianthus plant for almost any garden space and region. Here are some, but certainly not all of the varieties to choose from:

• The typical annual dianthus is the Dianthus chinensis, or Chinese pinks.
• Perennial varieties include Cheddar (Dianthus gratianopolitanus), Cottage (Dianthus plumarius) and Grass pinks (Dianthus armeria). The foliage on all of these is blue-gray and each comes in a rainbow of colors.
• Dianthus barbatus is the common Sweet William and a biennial. There are both double and single flowers and the variety reseeds itself.
• Allwood pinks (Dianthus x allwoodii) are long lasting with flowering extending at least 8 weeks. They are mostly double flowering and come in two sizes, 3 to 6 inches (8-15 cm) and 10 to 18 inches (25-46 cm) tall.