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Snapdragon

Dwarf Series: Bells™, Chimes™, Montego™

Intermediate/Tall Series: Aromas™, Arrow™, La Bella™, Liberty Classic™, Madame Butterfly™

 

1. Soil and pH Needs

Snapdragons require a well-drained, fertile soil.  They do not perform well in wet, poorly drained soils. 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 for optimum uptake of iron; 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. 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. Because they're quite drought-tolerant, snapdragons seldom need daily watering other than what they receive with rain; in prolonged periods of drought, however, watch that the soil doesn't get too dry.

 

2. Fertility

Snapdragons are moderate feeders in the landscape; and can have a crop life of three-four months. 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 areas of high irrigation and high temperatures it may be better to use a formulation with a slower release rate since higher temperatures will cause the fertilizer to be released quickly. In high pH soils (alkaline soils) additional iron or iron sulfate may be beneficial to reduce chlorosis (yellowing) of the foliage.  Yellow foliage on snapdragons may also be caused by a nitrogen deficiency within the plant. Both can be corrected with the proper supplemental fertilizers. 

 

Iron deficiency caused by high pH

 

3. Disease

Snapdragons are prone to several diseases which may be seen in the landscape. Anthracnose can be identified by the formation of yellow spots on both the leaves and stems. The spots will turn white and have a brown border. The leaves will die as will the entire plant if the stem is girdled. Downy mildew is usually found as a gray to white fungus lightly covering the underside of the foliage. Older plants will turn yellow, be stunted and die from the top down. Snapdragons are also susceptible to rust which will present itself as small yellow swellings on the leaves and stems that burst and release rust-colored spores. Concentric rings of spores will form around the initial spot. To help control foliar diseases, avoid wetting foliage and provide adequate air circulation between the plants. If overhead irrigation is used, water early in the day to allow foliage to dry before nightfall. 

 

Anthracnose on snapdragon stem

 

Concentric rings typical of rust

 

4. Insects

There are several pests that you may find on snapdragons: aphids, mites and thrips. Spider mites feed on the underside of the leaves which causes yellow spots to form.  This results in decreased plant growth and production. The nymphs and adults produce webbing that can cause cosmetic damage to the crop. Aphids feed on the plant sap. This halts growth, causing the leaves to become deformed. Aphids also excrete honeydew which causes sooty mold to develop and makes the plant unsightly. Thrips cause damage to the plant by piercing and sucking cells on the leaf surface. This causes silver-grey spots to form on the foliage. At high infection rates, the leaves may wither. Remember that healthy, vigorous plants are less susceptible to pest damage than unhealthy plants.  

 

Adult spider mites

  

Adult aphids

 

Adult Western Flower Thrips

 

5. Tips for Success

  • Snapdragons prefer full sun, and a well-drained soil.
  • Snapdragons perform best in the landscape in cool weather, and most cultivars can tolerate a light frost 
  • Remove weeds from the plantings that compete with snapdragons for moisture, nutrients and light.

Information provided by Syngenta Flowers