How to Grow Sweet Williams
How to Grow Sweet Williams (Dianthus Barbatus)in your Cottage Garden, tough and reliable for years of beautiful blooms.
How to Grow Sweet Williams (Dianthus Barbatus) is for those who want to add a tough but sweet-smelling cottage flower to their garden.
One of those easy flowers that grow well in many zones.
Learn what growing conditions Sweet William plants like, how to start them from seeds, and how to care for them for a long bloom time.
What you will learn about Growing Sweet Williams (Dianthus Barbatus)
- How to start Sweet Williams from seed
- Best growing conditions to care for Sweet William plants
- How to keep Sweet Williams flowering
- Are Sweet Williams a perennial or annual
- Are Sweet Williams poisonous to dogs or cats
Related: Garden Zones, what you need to know!
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Step 1: Choose the right location
Sweet Williams prefers growing in full sun but will tolerate light shade.
They tend to grow taller and get a bit floppy if they get too much shade so if this occurs just plant in a sunnier spot the next time.
The caveat to this is if you are in the South with hot summer temps, they will do a bit better with some afternoon shade.
They also prefer well-drained soil. Before planting, it’s important to prepare the soil by adding compost or well-rotted manure to improve its texture and fertility.
Sweet Williams can also be grown in containers if you have limited space.
They are hardy in zones 3 – 9 and can be grown alongside perennials, as a border to a flower bed, or in containers.
Step 2: Planting Sweet Williams
Sweet Williams can be grown from seeds or transplants. If you are starting from seeds, sow them indoors in early spring or directly in the ground in late summer or early fall.
Cover the seeds with a thin layer of soil and keep them moist until they germinate, which usually takes about 2-3 weeks. Transplants can be planted directly in the ground after the last frost.
When planting, space the plants about 6 to 12 inches apart and plant them at the same depth as they were in their container or the soil level in the seed tray.
Water the plants thoroughly after planting and keep the soil consistently moist until they establish themselves.
If starting indoors sow your seed in your containers 6 to 8 weeks prior to the first frost. I have an entire post on how I start seeds early here.
Or you can winter sow them as I share in this post. This is super easy and successful!
But my favorite way for Sweet Williams takes patience and is super easy. In late summer scatter the Sweet William seeds on weed-free soil where you want them to grow.
Don’t add a cover of soil, just firmly step on them to make sure there is good contact with the soil.
They like loose, rich soil that drains well so don’t press them in too firmly. Keep them watered and watch for the seedlings.
Thin the seedlings once they reach 3 inches tall to 12 inches apart.
I dig them up and replant them in another area rather than just tossing them in the compost heap or I pot them up to give to garden friends and neighbors.
Thinning helps prevent fungal disease and lets the plants grow healthily. By next Spring you should have beautiful sweet-smelling blooms.
Sometimes I don’t get to this job of thinning and they have grown fine, they just did not get as big as they could have.
We live in a dry climate so mildew is not typically an issue.
Step 3: Care and Maintenance
Sweet Williams require regular watering, especially during dry spells. They also benefit from regular fertilization with a balanced fertilizer, such as a 10-10-10 formula, applied every 4-6 weeks during the growing season.
I prefer adding compost each season which acts as a slow-release fertilizer.
To encourage bushier growth and more flowers, pinch back the tips of the plants when they reach about 6 inches in height. This will also help prevent them from becoming too leggy.
Sweet Williams can be prone to powdery mildew, so it’s important to space the plants properly to ensure good air circulation.
Do Sweet Williams repeat flower?
To keep your Sweet Williams blooming you will need to deadhead them.
Watch as the flowers begin to fade and pinch or cut back the stem to half of its growing height. These are my favorite snips for jobs like this.
If you grow a swath of Sweet Williams as I do then cutting each individual flower when it fades is too much work instead wait for the majority of the flowers to begin to fade and then cut with pruning shears all of the stems to half of the plant height.
Shearing allows you to deadhead all the flowers at once. This will also control the size of overgrown plants and encourage the flowers to bloom again.
Keep watered and watch for fresh blooms.
Let Sweet Williams reseed or not
If you want the Sweet Williams to reseed and grow for you again next season then towards the end of summer stop deadheading and let the seeds mature.
Leave all of the seeds to spread on their own for a lot of Sweet Williams or let a few fall to the ground and save the rest of the seeds to give away or plant in other parts of your garden.
To see how I save seeds just hop on over to my Seed Saving for more Garden Blooms article!
Why Grow Sweet Williams
Sweet Williams will perfume your garden, that is the main reason why I grow them. Many traditional cottage garden flowers are sweetly scented.
For more scented flowers for your garden here is an entire post dedicated to flowers to grow for a scented garden.
Adding scent to your garden adds another level of enjoyment.
Are Sweet Williams a Perennial?
Sweet Williams are a great biennial addition for Spring to Summer bloom with plenty of perfume.
Biennials grow the first year and then bloom the second. That is why you can plant them in late Summer/Early Fall to get growing, then they bloom the following Spring.
Sweet William Colors
They grow in various shades of red, pink, purple, and white. Some can have a variety of colors on one plant, which is fun too.
Here is a great mix to try Dianthus Sweet William Mix, with lots of colors, and plenty of seed.
This one was a happy accident of many colors cross-pollinating in my garden and producing this gorgeous multi-colored specimen.
They get to about 7 to 18 inches tall depending on the variety and where they are planted.
I have always grown mine from seed or transplanted seedlings from one spot in the garden to another but you can also propagate by cuttings or root divisions.
You can also start them indoors, click here to see my method.
Great for Containers
They do well in pots and can bring a spot of Spring color to many spaces.
Sow your seeds directly in a container filled with good potting soil and keep watered.
Keep in mind that pots and containers dry out more quickly so you may need to water them more frequently than your garden plants.
What makes gardening so easy for me is I tend to favor flowers and plants that thrive in my area. I give them what they need and let them go.
Are Sweet Williams poisonous to dogs?
Yes, they are mildly toxic to dogs and cats. Though, mildly toxic in most cases, ingestion, if not treated can result in extreme gastrointestinal issues.
Many flowers are toxic to dogs and cats so if you have pets that seem to want to eat your plants you may wish to put any of those types of plants into containers or areas out of their reach.
Or eliminate them from your garden.
For more info on how I garden visit my Lazy Gal Garden Guide posts.
I enjoy the information so much. Thank you.
I read your posts but always wonder how I can adapt your advise to my Pittsburgh PA zone. I have never tried to sow seeds in the fall. Would that work for me with Sweet William seeds? Thanks Pamela.
They would probably do great in your area. My trick is to sow heavily in a spot instead of one seed here and there. You can also sow them in Spring but you have to wait a year to get blooms. Though there is a type from Renees Seeds that will bloom the first year. I am giving those a try myself and will sow them this Spring.
I threw down seeds a few years back and am lucky to be blessed with the blooms every year. Thanks for sharing your garden experience and tips
Isn’t it wonderful to find a beautiful one that reseeds itself and fills your garden easily. Plus they smell so subtly sweet, they are just a great addition.
Hello Pamela, Your blog looking so beautiful with flowers. In your blog you suggested the great idea of growing sweet williams. Really, they will give the perfect and beautiful look to my garden. Thanks for sharing.
What zones for these flowers that you can sow in winter?
I planted some a year ago but they have not flowered.
Is there anything I can do to encourage blossoms?
Please let me know,
Many Sweet Williams (especially the heirloom varieties) are biennial and will not bloom until the second year so yours are right on track.
My Sweet Williams are biennial, so how do I get blooms every year? Do I need to plant them in a different spot every other year? This is my first year to get blooms.
I just let seeds fall in place and each year I get blooms. You can sow them in other areas you want as well, just save the seeds like I show in this post: https://www.flowerpatchfarmhouse.com/sow-your-seeds-in-fall/
Hope this helps.
I got a late start and planted sweet william seeds indoors a couple weeks ago; they have all sprouted. My question is, if I transplant outside them once they get bigger – say the end of July, will the plants survive the winter (Zone 7) and flower next spring?
Yes, they should do just fine, mine over winter easily.
Love the sweet William! Looking for more fragrant floy
I’m just a 60 year old gardener who hasn’t done it in years, and my mom God rest her soul hasn’t been around for 21 years to ask the questions-
I would love to be able to have the cheat sheet for growing Sweet Williams in my own garden. As a teenager I worked at a greenhouse where they grew cut mums but we also had sweet Williams and they became a favourite flower of mine and I’ve always wanted to grow them myself someday. Fast forward 30+ years and I’m glad I came across your advice here.
I’m in the southern hemisphere and have just begun growing Sweet Williams from seed and it didn’t say on the seed packet that they grow the first year and flower the next, I only found this out when I read your site. May I please have a copy of your Growing Sweet William Cheat Sheet?
The printable is now available in the blog post. Enjoy!
I only have a small garden area with terrible clay and broken bits of concrete in it but have 8 rose bushes that have been growing for years and giving me lovely perfumed blooms. Nothing much else has done any good.
I can’t afford to buy rich compost etc so if you have any suggestions I’d appreciate it. Thanks. Bev. I’m from Brisbane, Australia.
Have you tried to make your own compost? Here is a link to my article Easiest Compost Ever. Give it a try. It may work well for you.
I need to know when they bloom. Here in UK early September mine haven’t grown any flowering stems, possibly next year as I planted them out as young plants in May?
Yes, Sweet Williams are a biennial so you should get blooms next Spring.
This article is brilliant. I’m in Australia, and my Sweet William is doing very well in our spring sun. Thank you for your informative site, which is very well written and full of tips and hints. You gave me more info than I’d intended to find, and this is marvelous.
Thank you, I do try to be as thorough as I can.