What Is the Snapdragon's Foliage?

Leaf Description

• Snapdragon leaves range in length from less than an inch to 4 inches long. The University of Florida Extension describes snapdragon foliage as simple, alternate, oblong, spatulate, petiolate and entire. Simple concerns the leaf type, which is single instead of a series of leaflets attaching to the leaf's mid-rib. Leaves that are composed of multiple leaflets, such as those of roses and clovers, are referred to as being compound. Alternate means each leaf grows out of a separate node at alternating spots on the stem versus being symmetrically arranged. Oblong and spatulate indicate a slender oval shape, somewhat like a pie spatula with a rounded tip. Petiolate says that a leaf is attached to the plant stalk by a tiny stem. The stem becomes the leaf's mid-rib. Finally, entire means that the leaf edges are smooth and not indented.

Leaf Diseases

• Snapdragon rust, which is caused by the fungus Puccinia antirrhini, is one of the most serious ailments that attacks snapdragons. Swollen yellow spots on top of the leaves are connected to brown pustules containing rust spores. These mostly develop on leaf bottoms. The University of Arizona notes that infected plants lose water rapidly and dry up. The University of Illinois Extension says yellow flecks on the underside of leaves are the first sign of rust. These develop from eight to 14 days after spore germination, but pustules may appear as soon as 12 days after germination. In addition, powdery mildew (Oidium spp.), downy mildew (Peronospora antirrhini) and anthracnose (Colletotrichum antirrhini) are other fungal snapdragon diseases that discolor and stunt leaves, eventually killing the plants.

Watering Problems

• Improper watering practices can make snapdragons vulnerable to disease and pests, such as aphids that suck moisture from plants. It is best to irrigate snapdragons in the morning to avoid mid-day wilting, which saps plant strength and creates susceptibility to attack. Watering at soil level is best because overhead spraying causes fungal spores to travel from one plant to another. Tight clustering of snapdragons also increases the spread of disease and aphids. In humid areas, it may be necessary periodically to apply fungicides to keep snapdragon diseases under control. In the case of rust, the University of Illinois Extension recommends spraying all parts of young plants every seven to 14 days.

Observation

• When purchasing snapdragon sets from garden centers, it is important to choose disease-resistant varieties and to check leaves for signs of fungal problems. Once the flowers are planted, gardeners need to be vigilant about observing foliage for signs of illness. Infected plants need to be removed upon discovery and carefully discarded in covered trash cans. They should not be composted.