Nutrient Deficiencies of Vegetative Petunia

By Dharmalingam S. Pitchay, Amy L. Williams, James L. Gibson, Brian E. Whipker, Paul V. Nelson, John M. Dole, Brenda R. Cleveland and F.R. Walls

Fertility monitoring and management for vegetative petunias require a balancing of the plant's needs. Growers must be aware and manage the root substrate pH, electrical conductivity (EC) and provide adequate, but not excessive, levels of all essential elements.
Nutrient deficiency descriptions are unavailable for most floriculture crops, yet growers must often make quick diagnoses. A research project initiated at North Carolina State University in Raleigh documented deficiency symptoms in petunia 'Improved Charlie' to assist growers. Nutrient deficiency research was also conducted on the seed propagated petunia 'Purple Wave'. Despite their origin in propagation and plant features, deficiency symptoms are very similar. Pictures will be labeled within the article to identify petunia 'Purple Wave'. Using a plant diagnostic lab to identify the source of problems is still the best way to ensure accurate diagnoses, since many nutritional, physiological, insect and disease problems can mimic each other.

Disclainer: Growers should read and follow all label directions. Test the corrective procedure on a small number of plants prior to applying it to the entire crop.

Macronutrients · Micronutrients

Photograph	Description	Possible Causes and Management
Nitrogen (N) (top)
	Nitrogen-deficient petunias have mature leaves that turn greenish-yellow to a uniform light yellow. The young leaves are narrow and are darker green.	Low Substrate Nitrogen
	At the advanced stage, the lower leaves express a purplish pigmentation. Necrosis begins on the leaf tips and margins.
Phosphorus (P) (top)
	Leaves are smaller and develop dark-purple patches. The midvein becomes dark purple starting at the base and pigmentation moves toward the tip of the leaf.	Low Substrate Phosphorus
	Phosphorus-deficient plants are smaller in size.
	The deficiency progresses from dark-purple patches to a brown papery necrosis.
Potassium (K) (top)
	A yellow-green interveinal chlorosis appears on recently mature leaves. As symptoms progress, the chlorotic regions develop tan, papery, necrotic spots that fuse into larger patches.	Low Substrate Potassium
	Mature leaves turn completely tan and wither at the advanced stage.
Calcium (Ca) (top)
	Calcium-deficient plants are stunted and have smaller leaves, as compared to the control.	Low Substrate Calcium
	As symptoms progress, brown to dark-purple spots develop on the mid-regions of the young and recently mature leaves of the axillary shoots. The youngest leaves become deformed and are straplike in appearance, while the margins turn chlorotic.
	As the deficiency advances, purplish spotting quickly develops into necrotic areas on the youngest leaves. The recently mature leaves have large, purplish patches that appear on the margins moving in toward the midvein. Flowers wither prematurely.
Magnesium (Mg) (top)
	Magnesium-deficient plants have young and recently mature leaves that express a greenish-yellow cast. A faint interveinal chlorosis is observed on the recently mature and older leaves. Mature leaves develop a thin band of marginal chlorosis that ultimately progresses to a tannish-gray necrosis.	Low Substrate Magnesium
Sulfur (S) (top)
	The mature leaves of sulfur-deficient plants are light green while the young leaves are greenish-yellow.	Low Substrate Sulfur
	The overall size of the plant is severely stunted with very little axillary growth. Flowering is reduced compared to the control.
	Recently mature leaves turn greenish-yellow to light yellow as symptoms progress. Eventually, the yellow leaves wither and turn brown. The midvein turns brown, with necrosis progressing from the base of the leaf moving toward the leaf tip.

Photograph	Description	Possible Causes and Management
Boron (B) (top)
	Boron-deficient plants are severely stunted, compact and dull green when compared to the control.	Low Substrate Boron
	The growing point has a deformed rosettelike appearance and bud abortion is apparent. The young leaves are thick and a glossy dark green color exists.
	Some of the recently mature and mature leaves have a yellow-green chlorosis on the leaf tips that starts at the margin and move inward towards the midvein.
	As symptoms progress the midvein turns dark brown to black, starting at the base of the leaf moving toward the leaf tip. Brown necrotic spots fuse to create random brown patches on recently mature leaf margins.
Copper (Cu) (top)
	Copper-deficient leaves are smaller and narrower than the control leaves. Deficient leaves have deformed margins and express a light green interveinal chlorosis.	Low Substrate Copper
	Flower size is significantly smaller than the control.
Iron (Fe) (top)
	Initial symptoms develop as a distinct yellow-green interveinal chlorosis on the younger leaves. Symptoms progress from the leaf base to the tip.	Low Substrate Iron
	Severe iron deficiency results in the young leaves turning light yellow to white, while the oldest mature leaves remain green.
Manganese (Mn) (top)
	Young leaves of manganese-deficient plants are uniform greenish-yellow. The recently mature leaves develop a random light yellow interveinal chlorosis.	Low Substrate Manganese
Zinc (Zn) (top)
	A light-green chlorosis develops at the basal region of the young leaves. The young and recently mature leaves begin to buckle and twist, making them appear deformed.	Low Substrate Zinc
	Young leaf chlorosis turns to tan, papery, necrosis.
	Close-up of necrotic patches.
	Zinc-deficient leaves are smaller and duller green than the control. At the advanced stage, tissue is tannish-white and brittle.

Amy L. Williams, Dharmalingam S. Pitchay and James L. Gibson are graduate research assistants, Paul V. Nelson is professor in floriculture, John Dole is associate professor in floriculture, and Brian E. Whipker is assistant professor in floriculture at North Carolina State University, Department of Horticultural Science, Box 7609, Raleigh, NC 27695-7609. Bobby Walls and Brenda Cleveland are NCDA Agronomic Division Members NCDA&CS Agronomic Division, 4300 Reedy Creek Road Raleigh, NC 27607-6465. We would like to thank Paul Ecke Ranch, Encinitas, CA., Tom Abramowski, Rockwell Farms, Rockwell, N.C., and the North Carolina Commercial Flower Growers' for grant support, Paul Ecke Ranch for supplying the cuttings and Smithers-Oasis for supplying the propagation medium.

Disclainer: Growers should read and follow all label directions. Test the corrective procedure on a small number of plants prior to applying it to the entire crop.

© Copyright NC State University, 2002

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