Before I started gardening, it was safe to assume that I wasn’t able to recognize very many different types of plants. In fact, it was very seldom that “pre-gardening me” would have even noticed a pretty flower blooming next to me. One exception to this, however, occurred when I happened upon an insanely large planting of sweet william dianthus at a local park. In full bloom, the flowers were absolutely gorgeous! As you can imagine, I knew that they needed a place in my garden.
Sweet William (dianthus barbatus) is a biennial flower that produces large clusters of smaller, fragrant flowers. Though the color palette of these plants is somewhat limited, I’ve always been more than pleased to see the wide range of pinks, reds, and purple flowers that pop-up and bloom the summer after planting.
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Since these flowers are biennial, that means that we’ll need to do a little planning ahead of time. In general, biennial flowers begin growing in their first season, and then bloom in the second season of growth. Heirloom sweet williams behave consistently in this manner. However, the introduction of various hybrids may offer other options for the home gardener. The first year I grew these flowers in the cut flower garden, I planted a variety called ‘Amazon Neon Cherry’. When planted in the spring, this dianthus bloomed the first season. The downside, however, was that the seeds were extremely expensive (comparatively), and my blooms lacked any kind of scent. I’m honestly not certain whether or not this was a specific feature of the hybrid, or simply the result of an early planting indoors (about 6 weeks before the last frost dates). If you’ve had similar experiences, I’d love to know about them in comments! While I know the thought of waiting almost an entire year to see your flowers bloom is extremely off-putting to some growers, I definitely think that it’s worth the wait!
To accurately determine when sweet william should be planted, you’ll first need to make sure that the plants are hardy to your growing zone. Most seed packets label the plants as hardy to USDA zones 3-9, but that may vary depending upon your location. Prepare a planting site by removing the weeds and working the soil. The seeds of sweet william can easily be direct sown into their location or can be started indoors using seed trays if you wish to transplant later. Here in my zone, I like to wait until mid summer (around the end of July) before starting seeds for sweet william. This allows me to avoid planting them during the busiest part of the garden season (spring planting). Sweet william can also be planted in the spring, or even grown using the winter sowing method.
Once planted, sweet william requires very little care – which I love. The flowers are beautiful when used as cut flowers for bouquets. Additionally, these plants reseeds quite freely in my garden. If you’d like to avoid this, make certain to dead head any spent flowers. 
That’s really about it! I’d love to hear about your success with these beauties down below! Hope you’re having a wonderful day!
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Sometimes I wonder if they are truly or all biennial as I seem to have some in the same places for several years now. It could be that they have self sown. They can bloom twice if cut back when the flowers have faded.
I am growing some of these. Sowed them last year in late June. Relocated them this spring. Each bush is just under one foot tall and one foot wide They are beautiful, but they still haven’t bloomed (its now very late July). What am I doing wrong?
If they’re a foot tall, it sounds like they’ll be blooming soon. I would give it a little more time. Moving them may have delayed things. Good luck!