How to Grow and Care for Sweet William

Sweet William (Dianthus barbatus) is a short-lived, herbaceous perennial or biennial with a height of about 2 feet that is often planted as an annual flower. The flowering plant, with average pointed green leaves, is ideal for use in cottage gardens, perennial beds, or containers. The flowers come in many vibrant shades and are attractive to pollinators like butterflies, bees, and hummingbirds. Research suggests that sweet William is mildly toxic to pets and people.

Sweet William Care

Sweet William is easy to grow provided the following needs are met.

• Plant in rich, well-drained soil.
• Space plants about 8 inches apart as bedding plants to allow for the dense foliage that appears during the first year.
• Provide full, filtered sun but partial shade in hot temperatures.
• Irrigate regularly, but be careful not to overwater.

Light

Unless you live in a hot Southern region, sweet William likes a full sun position over any shade. They can tolerate light shade, but too much of it results in leggy, floppy plants. In hot regions, some afternoon shade is best to help prolong the bloom time.

Soil

Sweet William can tolerate many soil types, except wet, heavy conditions. A well-drained, fertile, loamy site is ideal. The plants can survive in soils with various pH levels too but often do best in a neutral to slightly alkaline one. Some growers add lime to the soil before planting.

Water

Water sweet William regularly through the growing season, but take care not to overwater. Waterlogged conditions promote fungal diseases in this species. A moist but not saturated substrate is best.

Temperature and Humidity

For a flowering plant, sweet William is relatively cold-hardy. It can survive light frosts, but deep freezes will result in the plant dying down. This species doesn't do well with high humidity, and temperatures above 85° Fahrenheit can result in dormancy.

Fertilizer

Sweet William should be fed with an all-purpose fertilizer every 6 to 8 weeks while they are growing. For the amount to use, follow product label instructions.

Pruning

Late winter or early spring is the best time to prune Sweet William. Cut at the spot just above the leaf nodes, as this is where new growth will spring from. If the plant is too bushy, trim off the stem tips. To encourage airflow, thin out the stems removing any that have become leggy and weak.

Propagating Sweet William

Propagating sweet William from cuttings is possible. However, because these plants are short-lived, many people simply purchase cold-treated plants during the spring to grow them as annuals.

Potting and Repotting

Sweet William plants do well in containers and planters due to their compact size. The pots can be grown indoors or out. Choose a 5-inch or slightly larger container with adequate drainage holes and fill with a rich potting pix and add a little compost. Place the containers in areas with full sun such as a windowsill.

If you notice any water pooling or root congestion, you should move the plant to a larger pot. The best time to do this is in the Spring before another growth spurt. Choose a pot that is a few inches larger in diameter than its current home. Terra cotta or unglazed ceramic pots are best for breathability and drainage. Add new soil and care for your Sweet William as usual.

How to Grow Sweet William From Seed

Sweet William is easy to grow from seed, but they don't typically bloom the first year. The seed can be sown into the ground in the late spring or early summer when there is no danger of frost. They prefer cool temperatures of around 50 to 55 degrees Fahrenheit and consistently moist soil for germination. Temperatures above 65 degrees Fahrenheit can result in weak, leggy growth.

These plants don't like to be overcrowded, so, as the seeds germinate, thin them out so there is adequate air circulation.

If you want to see blooms in the first year of planting, you could try sowing the seeds indoors in cell packs or containers six to eight weeks before the last spring frost. Harden them off and transplant the seedlings outside once the danger of frost has passed.

Overwintering

Protect your sweet William plants from the winter cold by cutting back dead foliage and blooms after flowering, but don't prune in the fall. Let the rest of the dead foliage fall to the ground to create a layer of protective mulch. Add to this a few more inches of mulch to insulate roots. If your plants are in containers outdoors, move pots away from areas that suffer from wind, snow, and ice.

Common Pests & Plant Diseases

Fungal diseases like rust and crown rot can be a problem for sweet William if it is planted in poorly drained soil or overwatered. It is also attractive to slugs and snails.

How to Get Sweet Williams to Bloom

Bloom Months

Under the correct conditions, sweet Williams can flower from May through to October in their flowering year.

How Long Does Sweet William Bloom?

Sweet William flowers will stay vibrant for up to ten days before fading.

How to Encourage More Blooms

Ensuring sweet William has moist but well-drained soil is crucial for healthy and abundant bloom production. Overly hot temperatures also impact flowering capabilities.

What Does Sweet William's Flowers Look and Smell Like?

With their small clusters of flowers, sweet Williams offers a splash of color right through the summer. Their bright range of colors includes reds, pinks, whites, purples, and bicolors. Some flowers are fragrant, but many cultivars are scentless. Their fringed and bearded petals are what give them their alternative "bearded pink" name.

Caring for Sweet William After It Blooms

Once blooming is complete, you can cut back any dead foliage and flowers so they don't continue to take energy from the plant.

Deadheading Sweet William Flowers

Deadheading spent flowers will also encourage more blooms. However, stop deadheading in the late summer to encourage self-seeding for new plants the following year.

Common Problems with Sweet William

Leaves are Curling

Curling leaves can indicate the presence of Fusarium wilt, a fungal disease. This disease can cause wilting, and the plant's overall health may decline. Since the pathogen is present in the soil, it can be challenging to eliminate once it has taken hold. Prevention is key, so be careful when handling the plants to avoid root damage, which can make them more susceptible to the disease. If transplanting your Sweet William, ensure that the new soil is healthy and free from infestations.

Leaves Have Yellow or Brown Spots

Yellow or Brown spots are a symptom of leaf spot. It will eventually lead to the death of the plant. You can protect the plant going forward with a fungicidal spray. Also avoid overhead watering as the spores are airborne.

Brown spots can also be caused by environmental factors such as high humidity and sitting water leaving spots on the leaves. Conversely, conditions that are too dry could lead to scorched patches.

Stem is Turning Yellow

If the stem of your plant is turning yellow, the plant may be receiving too much water. Doing so over time will eventually lead to root rot and mildew and irreversible damage to the plant. Reduce your watering immediately and check the soil. If it appears to be draining slowly, replace it with a dry, loose potting mix. Once the plant perks up, you can return to a regular watering schedule.