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Dianthus

Series: Dulce™, Diabunda™, Elation™, Charms™, Fandango™, Venti Parfait™, Super Parfait™

  

1. Soil and pH Needs

Dianthus are tolerant of a wide range of soil conditions, but prefer a rich soil with good drainage. Heavy clay soils will retard root growth and starve the plant of oxygen, which can lead to root diseases. Soil should be amended with fully composted organic matter prior to planting and in the case of clay soils the addition of Canadian sphagnum peat moss and well-rotted compost are good sources of organic matter that will aid in aeration. If possible, incorporate two to three inches of organic matter into the top six inches of soil. If adding organic matter, be aware that organic matter that has not been fully composted will tie up nitrogen and sulfur leading to nutrient deficiencies and poor growth.  Soil pH should be 5.5 - 6.2; and should be tested prior to planting but after adding any amendments. This can be done quite easily with a portable pH tester available for about $100. Mix one part soil with two parts distilled water, stir well and wait thirty minutes, then follow the instructions for using the pH meter. If pH is too low, the addition of lime is warranted. However, the rate will vary depending on how much you need to raise the pH and the type of soil you are dealing with. Clay soils or those with a lot of organic material have a high buffer capacity and require more lime than sandy soils, which have a low buffering capacity. A good soil testing lab can determine the lime requirement index (LRI) of your particular soil and can recommend types and rates of lime to use. The frequency of watering will depend on the type of soil, weather conditions and the amount of mulch. Dianthus plants need good air circulation and they should not be heavily mulched. Very light mulch at the base of the plant is sufficient for weed control.  Mulch will not only reduce soil water evaporation but will also reduce splashing of water onto the lower leaves, moderate soil temperatures and reduce weed competition.

 

2. Fertility

Dianthus are moderate feeders during their life cycle. An application of a balanced controlled-release fertilizer (CRF) such as 10-10-10 or 14-14-14 with a 3-4 month formulation applied to the bed at planting will keep the plants well fed, depending on the amount of irrigation required and the average daily temperature. In high pH soils (alkaline soils) additional iron or iron sulfate may be beneficial to reduce chlorosis (yellowing) of the foliage.  Yellow foliage on dianthus may also be caused by a nitrogen deficiency within the plant. Both can be corrected with the proper supplemental fertilizers. 

 

3. Disease

Dianthus are susceptible to several fungal diseases. Irrigating correctly can prevent most of the fungal diseases. Provide water early in the day to allow for plants to thoroughly dry, and utilize drip irrigation when possible. Fusarium infected plants first develop a dull green color and eventually wilt and turn straw-color. Symptoms often appear on one section of the plant. Plants may be attacked at any stage; young plants can suddenly dry up or older plants might develop a pale green color accompanied by wilting of lower leaves. This is frequently followed by a general wilting and death of the entire plant. Alternaria leaf spot is identified by pale tan to brown spots with purple borders that appear on the leaves. These can vary in color, size, and number. Dianthus flowers are also susceptible to Botrytis which causes the flowers turn a papery brown and become covered with gray, fuzzy masses. Senescing flowers are particularly susceptible. Tan to brown streaks can also develop on the leaves. These patches are often associated with flowers which have dropped onto the leaf surface. This disease is particularly troublesome during periods of extended cloudy, humid, wet weather. 

 

Alternaria leaf spot

 

Fusarium crown rot

 

4. Insects

There are three pests which may cause problems on Dianthus. Aphids are tiny soft bodied insects that cluster on the growing tips of leaves and flower stems, sucking plant juices. The plants become stunted and deformed. Spider mites feed on the underside of the leaves. This feeding causes yellow spots to form which results in decreased plant growth and production. Thrips cause damage to the plants by piercing or sucking out the cells on the leaf surface. This causes silvery grey spots on the foliage. At high infection levels leaves may wither. Thrips are also a primary vector for virus transmission. Remember that healthy, vigorous plants are less susceptible to pest damage than unhealthy plants.  

 

Aphid infestation

 

 

Adult Western Flower Thrips

 

5. Tips for Success

  • Dianthus plants need good air circulation and should not be heavily mulched.
  • Dianthus need at least six hours of sun.
  • Deadheading (removal of spent flowers) will prolong bloom time and help produce a fuller plant.
  • Remove weeds from the plantings that compete with the pansies/violas for moisture, nutrients and light.

 

Information provided by Syngenta Flowers