The Complete Guide to Growing Dianthus

Dianthus are attractive cottage garden flowers belonging to the same family as carnations. Also known as Pinks or Sweet Williams the flowers are known for their colorful appearance and spicy cinnamon-like fragrance.

Pinks grow in clumps or mounds that can reach up to 10 inches in height. From here attractive flowers emerge, happily reaching up to the sky. Taller varieties tower over other flowers and small shrubs. This makes them a great choice for mixed flower beds and borders. The compact growth habit of the plant, most varieties reach between 6 and 18 inches in height, means it is also a great container garden plant.

A popular bedding plant, Sweet William is one of the most commonly grown cultivars. 

As the informal name Pinks suggests these flowers usually come in shades of pink. Red and white shaded varieties can also be found. Flowering from May to October, dianthus can be grown as hardy annuals, biennials or perennials.

Warning: The foliage of dianthus can cause skin irritation in some people. If you have sensitive skin, wear gloves when handling the plants. Dianthus can also be mildly toxic to pets if ingested.

Dianthus Varieties

There are over 300 different species of dianthus. The majority are native to Asia and Eastern Europe. However, a few varieties originate in the North of Africa while one is indigenous to the northernmost parts of America.

The range of dianthus plants available means that whatever your situation and USDA zone you should be able to find a variety that suits you. Most dianthus plants grow in USDA zones 3 to 9 with little trouble. In these conditions the vast majority of pinks are herbaceous perennials.

Dianthus chinensis or Chinese pink is one of the most common annual varieties.

Rose De Mai is a particularly fragrant heirloom variety that produces attractive lilac colored flowers. The attractive First Love is a repeat flowering plant. It can also produce pink and white flowers at the same time.

Cottage pinks, Grass pinks and Cheddar are all reliable perennial cultivars. Coming in a range of colors, the flowers of these plants sit on a mass of blue-gray foliage. The hot pink Firewitch is another popular perennial variety.

Take your time to explore all the different, available varieties. These attractive flowers come in a range of pleasing patterns and shapes. 

The most common biennial dianthus is D. Barbatus or Sweet William. This is a reliable cultivar that produces both single and double flowers. It is also a self-seeding plant. This means that if you don’t deadhead or remove spent flowers the plant can go to seed and spread through your garden.

Allwood dianthus is the most long lasting variety, flowering can last for at least 8 weeks. Producing double flowers, allwood varieties come in two sizes. The compact variety reaches 3 to 6 inches in height and is ideal for container gardens. The larger variety can grow to around 10 to 18 inches.

At the other end of the scale, the alpine pink is the smallest of the dianthus plants. This cultivar reaches between 4 and 6 inches in height. It is ideal for small containers and rock gardens.

In cooler climates, if you don’t think that your dianthus plants will survive the winter try propagation, or harvesting the seeds. This allows you to grow new dianthus plants to enjoy next year. The new plants can be started in late winter undercover. A backyard greenhouse is a great way to overwinter plants. Once the last frost date has passed the young plants can be planted out in the garden.

Growing from Seed

Dianthus can be either purchased as young plants and planted straight into a flowerbed or started from seed. Starting from seed may require more action on your part but it allows you to choose from a wider range of varieties.

Sow seeds undercover 2 to 3 weeks before the last local frost date. Sow one seed per small pot or spaced out in a seed tray filled with a loamy soil mix. Cover the seeds with a thin layer of soil and moisten with a fine spray.

Cover the containers or trays with a plastic wrap, or place in a small propagator. This creates the effect of a mini greenhouse, helping to keep the seedlings warm and moist.

Once the seedlings have produced at least three true leaves they can be carefully transplanted into pots.

Grow the seedlings on until they reach a height of about 5 inches. Harden off the young plants before transplanting outside.

How to Plant Pinks

Dianthus does best in full sun positions. Pinks also grow in partial shade, but ideally need to receive about 6 hours of sun every day.

Wait until the last local frost date has passed before hardening off the plants and planting out.

Before planting work the soil over so that it is loose and well draining. Working in some organic matter, such as homemade compost, or slow release fertilizer helps to enrich the soil.

Overly saturated soil can lead to the plants developing root rot or other diseases. Try to loosen the soil to a depth of about 12 inches. This improves drainage. It also helps the root system establish itself.

Pinks do best in soil types that have an alkaline profile. If you are unsure of the condition of your soil, testing kits are readily available and easy to use.

Dianthus do best bright, full to partial sun positions in well draining soil. If you want to overwinter the plants they will need some form of protection from frosts and cold spells.

To plant, dig a hole in the soil large enough to hold the root system of the plant. When placed in the hole the plant should be at the same level as it was when in a container.

Space the plants so that they are 12 to 18 inches apart. Larger varieties need more space. Spacing correctly ensures air can circulate between the plants. This helps to prevent diseases such as rust and powdery mildew.

After planting, water well around the base of the plant. Aim to keep the foliage as dry as possible, this prevents mildew from forming. Don’t mulch.

In milder climates, if your pinks survive the winter, place a 1 inch top dressing of organic mulch around the base of the plants in the early spring. Homemade compost is an ideal top dressing. This gives your dianthus an early season boost, encouraging them to set flowers once again.

Planting in Containers

Pinks can also be planted in pots or containers. Your chosen container should be clean and have drainage holes in the bottom. Self-watering pots are a great option if you want a truly low maintenance garden.

Fill the container with fresh, well draining compost and plant as above.

When temperatures begin to fall move the containers undercover to protect the plants from winter frosts.

Caring for Dianthus

Once planted, dianthus is pleasingly easy to care for.

Water

Water the plants when the soil around them is dry. During dry periods, water at least once a week. Remember plants growing in containers require more regular watering than plants growing in the ground.

The easiest way to work out the dryness of the soil is to stick your finger into the soil. If it feels dry to the first knuckle, water sparingly. A soil moisture meter, such as the Bearbro Soil Moisture Meter, provides a more scientific means of measuring the moisture content of the soil.

If you are still unsure whether to water or not, wait a few days. It is better to slightly underwater the plants than try to correct the problems caused by overwatering.

Harvesting your own rainwater allows you to keep your plants hydrated without running up an expensive water bill.

Allow the soil to dry out slightly between waterings. This prevents the soil from becoming waterlogged and the plants from developing root rot. 

Fertilizer

Working a slow release fertilizer into the soil before planting gives dianthus all the nutritional boost the plants need.

If you don’t want to add slow release fertilizers to your soil, an all purpose liquid plant feed can be applied. One with a 20-10-20 ratio is ideal. This gives the plants an extra boost during the growing season. A liquid plant feed is easily incorporated into your watering routine. Fertilize the plants once a month during the growing season.

Pruning

Some varieties of dianthus are self-sowing. This means that if you don’t deadhead the spent flowers they go to seed. Once ripened the seeds naturally spread around your garden.

If you don’t want the plants to spread naturally, prune away the spent flowers. While some can simply be picked from the stem, a garden scissors allows you to cleanly remove the flowers without damaging the plant.

Older plants may develop dead spots in the center of their foliage. To cure this, divide the plant. Carefully dig the plant up and with a sharp, clean knife cut into several pieces. Remove any dead foliage and replant.

Winter Protection

Dianthus tolerates a light frost. The plants won’t survive a deep freeze. Additionally if temperatures constantly hit over 85 ℉ the plants will become dormant.

Gardeners in cooler climates may not be able to keep pinks over the winter period. If you want to try to keep the plants over winter cut away any dead or dying foliage before mulching around the base of the plant.

A thick 4 inch layer of mulch should keep all but the harshest frost’s out. Apply the mulch before the first frost of the season. After the last local frost date has passed remove the mulch.

Alternatively, cover the plants with a small cloche or mini greenhouse.

Placing a thick layer of organic mulch around the plants helps to protect them from winter frosts. Additionally as the mulch breaks down into the soil the plants receive an extra nutritional boost. 

Container plants can simply be moved undercover or to a more sheltered area.

If you don’t think you can keep the plants overwinter, propagation allows you to enjoy dianthus flowers year after year.

Propagation

You can propagate pinks by division, tip cuttings and layering. You can also grow the plants from seed.

To take cuttings remove the non-flowering stems from just below a leaf joint with a garden scissors. Trim away the lower leaves, allow only the top 4 or 5 leaves to remain. Dipping the cutting into rooting hormone helps to encourage propagation. However this isn’t necessary.

Place the cutting 3 inches deep in a container filled with fresh, well draining soil. Firm the soil down and water lightly. Keep the cutting moist. If it is successful roots will form within a few weeks.

Divisions are best made in the spring. To divide the plants, dig around the dianthus clump, to a depth of roughly 6 inches.

Use the spade to dig under the clump and carefully lift the root system from the soil. If the clump is particularly large use the spade to cut the clump in half. It can then be lifted in easy to manage sections.

Inspect the roots looking for any possible health issues. Discard any parts of the plant that appear unhealthy. This is often the case with central sections.

Use a spade or a garden fork to separate the clump into smaller sections. You can also use your hands. Each smaller section should have a healthy section of root and top growth.

Plant healthy sections back in the ground as soon as possible.

You can also harvest the plants from seed. However, only 1 in 20 spent flowers develop seeds so this can be a frustrating process.

To harvest from seed, allow the flowers to become spent and develop seed heads. Carefully remove the spent flowers from the plant and place in a paper bag or on a sheet of paper.

Squeeze each spent flower gently between your fingers. If there are seeds present they will fall into the bag or onto the paper. The seeds are black, round and small in appearance.

Place the seeds in a warm, dry place to dry out for a few days. Don’t place the seeds anywhere where the wind can blow them away.

Once dry store the seeds in a paper envelope until you are ready to sow. Remember to label the envelope with the name of the plant and the date. The older the seeds become the less viable they are.

Common Pests and Diseases

Many varieties of dianthus are pleasingly hardy and disease resistant. Keeping the plant in well-draining soil and correctly spacing so that air can circulate prevents most problems.

Aphids may target your flowers. These can be removed with a blast from a hosepipe. Alternatively wiping a soapy water solution or neem oil onto the foliage removes most infestations.

Carnation flies can target dianthus plants. These pests lay eggs on the foliage of the plant. Once the eggs hatch, larvae burrows down into the plant’s stem. To prevent carnation flies from targeting your plants, plant alongside garlic. The aroma of garlic plants deters carnation flies.

Bright and colorful the delicate flowers of the dianthus plant come in a range of shapes and sizes. Growing a range of plants together in a border or container is just as effective as mixing the plants with others in a color packed flower bed. 

A popular cottage-garden style flower, the colorful, fragrant blooms are also popular with pollinating insects, hummingbirds and butterflies. Bright and cheerful, the easy to grow dianthus is a great way to bring color and layers to your garden.