Nutrient Deficiencies of Mimulus

By John Dole, Dharmalingam S. Pitchay, James L. Gibson, Brian E. Whipker, Paul V. Nelson, Bobby Walls, and Brenda Cleveland

Fertility monitoring and management for mimulus requires 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 for mimulus.
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 mimulus ('Jelly Bean White') to assist growers. 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 plants are noticeably smaller in size, as compared to the control. The lower portion of the stem turns pink and the lower leaves are light green.	Low Substrate Nitrogen
	As symptoms progress, the lower leaves turn pale yellow and necrotic margins appear.
	Upper surfaces of older leaves become yellow-green while lower surfaces turn rose colored. Leaf size is also reduced.
Phosphorus (P) (top)
	Phosphorus-deficient plants develop darker-green leaves that have a distinctive, needlelike appearance, as compared to the control.	Low Substrate Phosphorus
	Lower leaves of deficient plants develop blackish-brown spotting as symptoms progress.
	The spotting quickly coalesces into complete leaf necrosis. Mature leaves shrivel rapidly. The typical symptom of lower leaf purpling, which is associated with phosphorus deficiency, does not occur with 'Jelly Bean White' mimulus.
Potassium (K) (top)
	Potassium-deficient plants have upper leaves that are darker green when compared to the control. Plants are also 35 percent shorter. Axillary shoot development is restricted.	Low Substrate Potassium
	As symptoms advance, the mature leaves begin to bend downward. Soon after, leaf tip necrosis begins.
Calcium (Ca) (top)
	Calcium-deficient plants are 40 percent shorter and the mature leaves are darker green, as compared to the control.	Low Substrate Calcium
	As symptoms progress, the youngest leaves of deficient plants develop tip burn.
	As deficiency symptoms become more severe, the upper, youngest leaves and growing tips develop necrosis. The axillary shoot tips also express tip burn. (Not pictured) root development is severely reduced with calcium deficiency.
Magnesium (Mg) (top)
	A comparison of mature leaves from a control plant (L) and magnesium-deficient plant (R), which shows the progression from a tip mottling to tip necrosis as symptoms advance.	Low Substrate Magnesium
Sulfur (S) (top)
	Sulfur-deficient plants have older mature leaves that remain dark green, young leaves that turn light green and the axillary shoots become greenish-yellow.	Low Substrate Sulfur
	As symptoms progress, the most recently mature leaves of deficient plants develop a diamond-shaped tip burn.

Photograph	Description	Possible Causes and Management
Boron (B) (top)
	Growth of boron-deficient plants is stunted by 45 percent.	Low Substrate Boron
	With boron deficiency, recently mature leaves lose their glossy sheen. Terminal growth is aborted and around the growing point a multitude of axillary shoots give a rosettelike appearance.
Copper (Cu) (top)
	Initial symptoms of copper deficiency include lighter green leaves, smaller plant growth (35 percent), and the upper two-thirds of the plant lack axillary shoot development, as compared to the control.	Low Substrate Copper
	Both mature and young leaves have a greenish-yellow appearance as compared to the control.
	The growing point and the axillary growth are olive green; recently mature leaves also develop necrosis in the interior of the blade.
Iron (Fe) (top)
	Initial symptoms develop as chlorosis of the younger leaves.	Low Substrate Iron
	As deficiency symptoms progress, young leaves develop a bright-yellow color.
	Advanced deficiency symptoms result in the young leaves turning bleach-white and necrosis quickly follows.
Manganese (Mn) (top)
	Manganese-deficient plants develop uniform light green color on the youngest leaves. Axillary development is poor.	Low Substrate Manganese
	As symptoms advance, the recently mature leaves develop a patchlike necrosis within the blade interior.
	With advanced symptoms, the overall plant is paler green, and the necrotic patches fuse together on the recently matured leaves.
Zinc (Zn) (top)
	A close-up comparison of normal leaves to zinc-deficient leaves. For deficient plants, the young leaves are narrower and the leaf tips of the mature leaves are paler green. Plants were similar in height, but axillary development of deficient plants was significantly reduced.	Low Substrate Zinc

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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