Is it necessary to deadhead sweet William? Expert advice for thriving flowers that look good all summer long

Sweet William, or Dianthus barbatus, are the ultimate cottage garden plant. A riot of pinks, whites, purples and reds with charming, old-fashioned blooms. In recent years, I have been a little obsessed with the 'Nigricens' group, which produces stems of solid purple-brown (almost black) blooms. Grown in a pot with something punchy like Viola ‘Tiger Eye’, this sweet William is hard to beat.

While all sweet William varieties are low-maintenance and relatively easy to grow, a little deadheading can go a long way in terms of longevity and keeping your borders and pots in good shape. Spending five minutes trimming every few days can really make all the difference, in my experience.

So, if you know how to grow sweet William but want some advice on trimming the blooms, you have come to the right place. Here's everything I know about how to deadhead sweet William.

Is it necessary to deadhead sweet William?

Whatever varieties of sweet William you enjoy, deadheading is an important job to add to your summer gardening checklist. Not only will it keep your yard looking good, but you can squeeze out as many new flowering stems as possible, sometimes right through until September and October.

If you enjoy bubblegum pink blooms, try this 'Baby Doll' sweet William variety, with seeds now available to order from Amazon.

When and how to deadhead sweet William

Sweet Williams can be grown in most regions and US hardiness zones, regardless of climate. They can either be sown as biennials, meaning they will flower the following year, or picked up from garden stores and treated as an annual that will last only until the first frost.

Deadheading dianthus and sweet Williams is one of those easy garden tasks that can have a big payoff. Once those first domes of flowers start to go over, usually around early summer, when the petals are dropping or browning, that is a good time to snip.

Doing so will hopefully coax the plant to keep going, often giving you a second, slightly smaller flush of flowers later in the season.

I tend to deadhead sweet William in borders and in pots, especially if I’ve gone to the trouble of pairing it with other cottage garden plants in containers, as you want to keep things looking neat and tidy.

Use something like these highly rated Felco F2 pruners, available from Amazon, which will easily cut through flower stems. Cut green stems down to the base of the plant, which should encourage new flowers to shoot.

Of course, you can leave these fading flowers to stand, but if you want to encourage more flowers, it is a good idea to trim these stems earlier in the summer.

If you’re lucky, the plant will push out new stems, giving you a second flush. Not always guaranteed, but definitely possible, especially if the summer’s been mild or you’ve kept your plants well-watered and fed.

For feeding, I would suggest a bloom booster or an organic tomato feed, like this fertilizer from Dr Earth, available from Amazon now.

Once we reach late summer, however, that is the point I would suggest leaving the faded flowers in place.

With any luck, these stalks will produce seeds you can collect and sow for next year's displays. So, from September onwards, it is probably best to stop deadheading and enjoy the end of the growing season.

FAQs

Can you compost trimmed sweet William stems?

Yes, all sweet William flowers, stems and leaves can be added to your compost heap. This green waste will quickly break down, just be sure to snip longer stems up into small bits (no more than a few inches), which will help with the composting rate.

While sweet Williams are tough plants, during hot summers, it can help to complete some deep watering as well as deadheading, which should boost flower production for as long as possible.

For more yard maintenance inspiration, see our guide on deadheading agapanthus, to keep your borders looking good late into the fall months.

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