Planting sweet William in late spring will usually produce flowers the following year, although some new cultivars bloom in the first year if you start the seeds early enough. Research suggests that sweet William is mildly toxic to pets and people.
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.
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.
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
With their small clusters of flowers, sweet Williams offers a splash of color right through the summer. Under the correct conditions, sweet Williams can flower from May through to October in their flowering year. 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. Ensuring sweet William has moist but well-drained soil is crucial for healthy and abundant bloom production. Overly hot temperatures also impact flowering capabilities. 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.
