Planting sweet williams: sowing & propagation

Planting pretty sweet williams is also easy for the amateur gardener – if you offer the flowering perennial the ideal location, you can look forward to lush flowering.

Sweet williams (Dianthus barbatus) are annual to perennial herbaceous plants often seen in cottage gardens. We have listed other characteristics and which varieties of sweet william are particularly pretty in our review article. Here we explain everything important about the ideal location and correct planting of the sweet william.

Planting sweet williams

If a suitable location with certain characteristics has been chosen, then a healthy and long flowering sweet william can be cultivated in the garden or on the balcony and terrace. Read here what you should consider when planting.

The right location for sweet william

The best conditions for healthy growth and abundant flowering are a full sun location, but at least light partial shade. The soil should be nutritious, well-drained and always fresh. Too much shade will result in less abundant flowering. Very heavy loam or clay soils can be prepared with sand or permeable plant soil, for example – a loamy-humic garden soil is ideal for the sweet william. You do not necessarily have to have a garden to enjoy the beautiful sweet william, as it also feels very much at home in a container. Here, too, care should be taken to ensure a suitable location and a high-quality substrate. Our peat-free Plantura Organic All Purpose Compost, for example, consists of coconut and wood fibres as well as quality compost, among other things, offering the sweet william an optimal soil texture. In addition, the substrate is already supplied with mainly organic bio-fertiliser.

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Sowing and growing your own sweet williams

Pre-grown sweet williams can be found in pots in the trade, but sowing is easy and the variety in the seed range is much greater than with young plants. Therefore, we explain step by step how to proceed with sowing:

• You can collect the seeds from your own sweet williams, although they are not varietal. This means that the form of the plant will be a surprise.
• Purchased seeds are propagated purely by variety and promise a certain appearance of flowering.
• The optimal period for sowing in the open is between the beginning of May and July, at temperatures between 15 and 20 °C.
• Alternatively, the seeds can be sown in late summer, after the hot midsummer.
• The soil should be loosened with a rake and weeds removed.
• Moisten the sowing site to prevent the seeds from being washed away afterwards.
• The seed should be distributed at a distance of approx. 20 cm and pressed a little into the soil.
• If sowing was successful, you can look forward to the first cotyledons after 2 to 3 weeks.

Tip: Without precultivation, sweet williams will not flower until the second year. For this reason, forward-thinking gardeners sow a few seeds each year to have permanently flowering plants in the garden or on the balcony and terrace.

Alternatively, sweet william seeds can be grown on the windowsill from mid-March:

• Fill a mini greenhouse or seed tray with substrate.
• A suitable substrate is low-nutrient growing soil such as our Plantura Organic Herb & Seedling Compost, which ensures strong and healthy root growth and is also peat-free.
• Spread the seeds 2 cm apart and press them 1 cm deep into the substrate.
• The cultivation should always be kept moist, but not too wet.
• Place the freshly sown seeds on a light windowsill, but protected from direct sunlight.
• The temperature should be 15 to 20 °C.
• After 2 weeks you will already see cotyledons – if the first real leaves form, you can start pricking out into larger pots.
• To encourage compact growth, place the pots in a slightly cooler place – approx. 15 °C is ideal.
• Once the last late frosts in May are over, the young plants may be planted in the open ground.

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Instructions for repotting

Whether bought or grown on the windowsill, here is a brief guide to planting this beautiful flowering perennial:

• Planting out in the open ground is done in May after the last late frosts.
• Depending on the size of the sweet william, a planting hole is dug.
• If the soil is heavily compacted, feel free to dig a little deeper to create a drainage layer.
• This layer consists of chippings or gravel, for example, and ensures good water permeability.
• Although the soil should always be kept moist – waterlogging is also not tolerated by the sweet william.
• Plant the sweet william so deep that the leaf rosette is completely above the ground.
• Make sure that the planting distance is 20 cm.

Tip: If the sweet william is planted in rows, for example to produce cut flowers, the distance should be 25 cm.

• Groups of at least 5 sweet william plants look very attractive.
• Last but not least, water the plants.

The procedure for planting in containers is similar. Choose a pot size that gives the plants a distance of 10 cm to the edge. The pot should also have a water drainage hole. A drainage layer – for example of expanded clay – is important, to avoid waterlogging.

So that you can enjoy healthy plants for as long as possible, we have summarised everything you need to know about the care of sweet Williams.

Propagating sweet williams

The most common method of propagating sweet williams is by seed. After the flowering period between June and August, the capsule fruits emerge, which are about 1 cm in size and also contain the sweet william seeds. If the capsules are slightly open, the seeds are ripe. Early flowering varieties can be sown directly, very late flowering specimens should be stored in a dark, cool and dry place. The next year they are sown as described.

Alternatively, sweet williams can be propagated vegetatively via cuttings. However, this is only advisable in the first year of vegetation, i.e. the year of sowing or planting, as the sweet william usually dies after flowering. To have flowering specimens in the garden the following year, cut off a 5 to 10 cm long shoot and stick it in seed compost. Our Plantura Organic Herb & Seedling Compost, for example, is lower in nutrients than potting soil and thus promotes root development of young plants. Rooting takes place after 3 to 4 weeks, provided the soil temperature is around 20 °C. The air temperature, on the other hand, should be somewhat cooler and around 12 °C, which is why a heating mat is ideal for growing. The cool temperature and regular pruning of the young plants result in compact growth and abundant flowering. If you can see the first new leaves, roots have successfully formed and the young plants can be planted in the desired place in the garden or in an appropriately sized planter.