Sweet Williams, which stand out because of the frilly edges on the blooms, are a nice addition to flowerbeds. Their colorful white, pink, red and purple blooms make them a popular choice for flowerbeds, borders and window boxes. The spicy fragrance of the flowers makes them ideal for cut flower arrangements.
Sweet Williams, also known as dianthus barbatus, are rather unusual in that they grow as annuals in climates with cooler temperatures and perennials in warmer climates. The bad news is that they are relatively short-lived (even as perennials). The good news is that the plants often reseed themselves, eliminating the need to buy new ones for planting. Just leave the dried blooms in place.
Sweet William is considered a biennial flower, which means that the plant will begin to bloom during its second year of growth. Expect only leaves during the first year.
Sweet William plants can be found in dwarf forms that grow six to eight inches in height. Full-sized plants grow 12 to 18 inches in height.
Planting Sweet William
Sweet William plants, which look very similar to carnations, can be grown from seeds, cuttings or plant divisions. If planting seeds, plan on starting them indoors six to eight weeks before the last frost for spring blooms. The young seedlings generally transplant well and can be set outdoors after the last frost.
Seeds can also be sown directly in the flower garden early in the season. Cover the seeds with one-eighth inch of soil and water thoroughly, but do not over water.
If planting Sweet William plants, place them about four to six inches apart. They do tolerate some crowding.
Sweet Williams prefer full sun, but will tolerate light shade. The soil should be rich with nutrients. It is best if the soil is loose and well drained. Maintain the soil so that is it moist to slightly dry.
Seeds and plants benefit from an initial application of a general all-purpose fertilizer at planting time. Plants can be fertilized on a monthly basis throughout the growing season.
Sweet William Pest and Diseases
Nematodes, which look like microscopic round worms, can be a problem for Sweet Williams. If you see nematode damage, visit your garden center for treatments.
Sweet William plants are susceptible to fusarium wilt, leaf spot, rust, root rot, gray mold and southern blight.
The yellowing of new growth is an indication of fusarium wilt. The plants are stunted and the leaves will die after turning yellow. It may be necessary to fumigate the soil.
Leaf spot is present when the leaves get yellowish brown withered spots surrounded by a purplish margin. Treatment may involve the use of a fungicide.
In the case of rust, pustules will appear on the underside of the leaves. Avoid watering from above and prune off infected parts of the plant. Treatment with a fungicide may be necessary.
Root rot is especially prevalent in wet conditions and starts by attacking the roots. The disease can also move up the stem. Treatment with a fungicide may be necessary.
Gray mold is one of the more destructive diseases that attach sweet Williams. High humidity provides the moisture that is needed for the spores to germinate and spread. Treatment requires the use of a fungicide.
Southern blight, also called southern wilt, southern stem rot and southern root rot, results from infection by the soil-borne fungus and a fungicide treatment may be necessary.
Interested in learning more about nematodes? Be sure to check this website out.
This article goes into more detail about Sweet William pests and diseases.
Want to learn more about Sweet William Flowers?
Additional information about controlling diseases that affect sweet William plants is available at the following websites:
UC Davis Guide to Pythium Root Rot.
The UC Davis Guide to Gray Mold.
The UC Davis Guide to Southern Blight.
Loretta Fay Henegar says
Do u have any photos of a plant shoot on what they look like so I don’t accidentally pull one out thinking it may be a weed. My cousin sent me some of her seeds from her garden. Thank you on advance for any help & photo if you have one to send me.
I started Sweet willam plants by seed never got the starts set out in a crowded shallow bowl for plants. They are about 56 inches tall healthy looking but now it is fall what do I do with them? I did not know that they were biennial so was waiting for the flowrs to come but guess that will not happen. Now what do I do with them.
Camille Buck says
It’s the end of June, and my dwarf perennial’s blooms are fading to a finish. If Icut them back, will they rebloom this season? What can I do to prevent the large areas from ugly?
Are the plants soft???
The plant almost looks like a thistle before blooming.
Jay Andrews says
What type of fertilizer, and how often, should be used for Sweet Williams?
I have sweet William’s that come up and bloom every year even though we live in Pennsylvania where it gets very cold. I never thought they would come back but they have for the last 3 yrs.