Horticulture Magazine

How To Water And Feed Dianthus

water being poured onto flowering dianthus from a green watering can

Dianthus, the Flower of the Greek god Zeus, is, in fact, the name of a genus that includes three super-popular flowering plants: Carnations, Pinks, and Sweet Williams. 

Dianthus, as a genus, is a little too often typecast and sometimes mischaracterised as being suited best for cottage gardens.

To correct the record, though Dianthus Sweet Williams may well be cottage garden mainstays, we submit that Dianthus Carnations are ‘courtyard garden classics’. 

Imagery and video featured in this article was commissioned by Horticulture.co.uk in collaboration with Organic Gardener Emily Cupit.

Carnation flowers with their pastel, genteel shades, refined looks, and subtle charms are well-suited for formal gardens as well, with that restrained, conservative glaucous foliage putting the final touches on the ‘formal’ dress code.

pink and red flowering dianthus plant with green foliage in the background

Whether it’s ruffled Carnations, fringed Pinks or dainty Sweet Williams that are most to your taste, you will get the best out of your plants if you follow these watering and feeding guidelines.

Watering

potted dianthus being watered

Where watering Dianthus is concerned, one had better start with soil and drainage.

All types of Dianthus are quite susceptible to root rot, crown rot, and stem rot (yes, all three) so soil must drain very well. 

To facilitate very good drainage – besides other factors – soil should not be heavy or clayey; at the same time, be mindful that Dianthus need a soil pH level from Neutral to Slightly Alkaline.

Be sure that containers and pots have drainage holes.

watering in the roots of a potted dianthus plant

As a general rule, assuming there is no rain and you’re enjoying ‘normal’ weather, give open-ground Dianthus an inch of water per week.

In hot weather water them twice a week.

Do not keep the soil consistently moist – let the soil just dry out between waterings.

This is especially important in the winter when you should also decrease the amount and frequency of watering.

To water by feel, allow the soil to dry out to a depth of 3 to 4 centimetres before watering again. 

pink flowering dianthus with nasturtium plant in the background

In hot weather do monitor soil moisture levels and especially so for containerised Dianthus plants.

If the container’s soil does not include moisture-retentive media, it will dry out very soon in high heat.

It would be well to water at soil level though this is not so critical for Dianthus as for some other plants.

However, virtually all flowering plants are best watered by mid-morning.

Feeding

all purpose concentrate fertiliser being held up with a large garden and greenhouse in the background

Though Dianthus are not heavy feeders and perform perfectly well without fertilising, they do require rich, fertile soil – that is a ‘non-negotiable’.

When planting Dianthus of any kind, till the soil to a depth of about 25 centimetres and amend with a generous quantity of organic compost or humus – that will do for ‘fertiliser’.

fertiliser being poured into a small measuring container

You may amend the soil with well-rotted manure too but do not use chicken manure for Dianthus.

(And while you’re amending the soil, you could also look into drainage, and add grit, sand, or perlite, as appropriate.)

Feeding Dianthus is an ‘extra’ and if you can do it, all the better.

measuring container filled with plant fertiliser being poured into a watering can

What with the thousands of cultivars of Carnations, Pinks, and Sweet Williams, different groupings have slightly different ‘feeding preferences,’ so to speak. 

That said, you can’t go wrong feeding any Dianthus by either:

  • Applying once in early spring and again in late summer a controlled-release or slow-release balanced fertiliser like Miracle-Gro Shake ’n’ Feed All Purpose Continuous Release or Osmocote Controlled Release Plant Food, or,
  • Feeding every few weeks with a balanced liquid fertiliser like Miracle-Gro All Purpose or a special-purpose formula such as Grow-More’s 3-6-6 Flower and Bloom.

We suggest that for Dianthus you apply fertiliser at 70-80% of the proportion or quantity indicated in the manufacturer’s directions.

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