Nutrient Deficiencies of Vegetative Strawflower Bracteantha bracteata 'Matilda Yellow'


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

Fertility monitoring and management for Bracteantha bracteata 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.
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 Bracteantha bracteata 'Matilda Yellow' 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

Macronutrients
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Description

Possible Causes and Management
Nitrogen (N) (top)
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Nitrogen-deficient plants are noticeably smaller compared to the control. Flowering occurs earlier than control plants.

Low Substrate Nitrogen
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A comparison of nitrogen deficient young and recently mature leaves: Leaves are light green and slightly narrower than the control.

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With advanced symptoms the lower mature leaves are chlorotic and the upper-portion of the plant has a pale green color. Flower stalks are longer than the control and appear light greenish-yellow in color.

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A close-up of the basal region of the plant shows a chlorosis on the lower mature leaves. The lowest oldest mature leaves have a yellow chlorosis starting at the leaf tips that progresses to the leaf base, which ultimately turns brown and withers.

Phosphorus (P) (top)
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Phosphorus-deficient plants are stunted and have darker green leaves compared to the control.

Low Substrate Phosphorus
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Overall phosphorus-deficient plants have a dull green cast. Chlorosis affects the mature leaf tips, which turn light yellow then brown. As symptoms progress the plants remain stunted with little axillary development.

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Chlorosis begins at the leaf tip as a yellow color which eventually becomes necrotic and progresses to the base of the leaf. The necrotic leaf tips often curl and wither.

Potassium (K) (top)
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Initial symptoms show that the young to recently mature leaves become chlorotic. The young leaves are also narrower than the control and their margins are beginning to roll under. Overall the plants are shorter than the control and the lower mature leaves have a darker green color.

Low Substrate Potassium
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The youngest leaves are light green and have a brown leaf tip necrosis.

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The young and recently mature leaves have a downward architecture and are slightly twisted. The upper mature leaves have a greenish-gray chlorosis at the leaf tips and margins.

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At the advanced stage, the margins and tips of the mature leaves turn a rusty-brown color. This region may also appear mottled.

Calcium (Ca) (top)
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Initial symptoms for calcium-deficient plants shows black necrotic spots on the midveins beginning at the base of the young and recently mature leaves.

Low Substrate Calcium
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As symptoms progress, the young leaves become needle-like and deformed. The upper recently mature leaves have a random interveinal chlorosis and the midveins have necrotic spots which fuse to form grayish-black patches.

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At advanced stages the plant size is much smaller than the control. Young flower buds turn brown and develop necrotic spots, which in turn abort. Complete withering of the young growth is followed by total necrosis of the shoot tip.

Magnesium (Mg) (top)
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Initial symptoms show a light green chlorosis on the recently mature and mature leaves.

Low Substrate Magnesium
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The recently mature and mature leaves have a curled leaf architecture. Margins bow downward and give the appearance of a cup-shaped leaf. Faint light brown spots are fusing into patches on the chlorotic leaf tips.

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As symptoms progress the yellow-green chlorotic tips of the recently mature and mature leaves turn brown and papery. The leaf tips continue to bow downward and some leaf tips are curling.

Sulfur (S) (top)
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Sulfur-deficient plants are smaller than the control. There is less axillary growth and plants are thin and spindly. The young and recently mature leaves are narrower (sword-like) and have a lime green color.

Low Substrate Sulfur
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The young and recently mature leaves are becoming narrow because the margins roll under. A progression in color from the youngest to the mature leaves: The youngest are lime green as compared to the medium green mature leaves that resemble the control.

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The stem is light green and there is little to no axillary growth in the shoot.

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With advanced sulfur deficiency the leaf tips and margins of the chlorotic areas turn light yellow to white, followed by a brown necrosis.

Micronutrients (top)
Photograph

Description

Possible Causes and Management
Boron (B) (top)
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Initial symptoms of boron-deficiency show that the youngest leaves around the growing point are deformed. The basal regions of the youngest leaves are wrinkled and twisted.

Low Substrate Boron
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As symptoms progress the axillary buds develop a brown necrosis and abort, many times flowering ceases. The surrounding young leaves develop a black necrosis and wither.

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In advanced stages the young to mature leaves have a wider and whiter basal midvein that turns brown and moves from the leaf base toward the tip. Chlorosis and necrosis occurs on the youngest leaves which are very small and deformed. The upper mature leaves are glossy and thick. Some of the flower buds at the growing point are underdeveloped or have aborted.

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Overall in advanced stages the plants are very stunted and compact with a thick canopy. Shoot elongation is less than the control and the mature leaves are wider with a drooping architecture. Often the plants are rigid to the touch with the leaves having a leathery texture.

Copper (Cu) (top)
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Initial symptoms of copper-deficiency show that the plant is a uniform light green color when compared to the control.

Low Substrate Copper
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As symptoms progress the recently mature and mature leaves cup downward and their leaf tips arch upward. The young leaves have developed brown necrotic patches on the tips.

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Flowers and flower buds of copper-deficient plants are bright yellow compared to the yellowish-orange control buds.

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With advanced copper-deficiency the youngest and young leaves have become needle-like and have a brown necrosis that causes them to be very brittle.

Iron (Fe) (top)
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Initial symptoms develop as either a uniform or random light green interveinal chlorosis on the younger leaves.

Low Substrate Iron
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As symptoms progress to an intermediate stage, the interveinal chlorosis becomes more visible.

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At advanced stages the young leaves range from having a yellow-green interveinal chlorosis to a uniform light yellow chlorosis. The recently mature leaves have a greenish-yellow interveinal chlorosis which starts at the tips and progresses to the base. A faint whitish-yellow marginal chlorosis is on the recently mature leaves.

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Leaf comparison: The young and recently mature leaves are yellowish-white and are beginning to show necrosis on the leaf tips as marginal scorching. The tips are withered, shriveled and curled upright. Interveinal chlorosis or a uniform chlorosis are also apparent on some young and recently mature leaves. The lower mature leaves are a dull green color.

Manganese (Mn) (top)
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Initial symptoms for manganese-deficient plants shows a lime green uniform chlorosis of the young to upper mature leaves.

Low Substrate Manganese
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The young and recently mature leaves appear swollen (wider) than the control. The midrib on the affected recently mature leaves is a dark green color. Tan to white, shiny, sunken and undefined patches are randomly appearing on the recently mature leaves.

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Manganese deficient plants at the advanced stage are overall a light lime green color and have a dense canopy because of less axillary elongation.

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The lower oldest mature leaves are dark green with a yellow marginal chlorosis on the tips. A brown papery necrosis is on the leaf tips of the recently mature and mature leaves. These leaf tips are curling upward.

Zinc (Zn) (top)
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Some recently mature leaf margins are deformed causing the leaf tip to turn to one side and cup downward.

Low Substrate Zinc
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Leaf comparison to the control: young and recently mature leaves are twisting and the margins are rolling under.

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The youngest to the recently mature leaves have random brown necrotic spots on their tips. These spots fuse into large brown patches and the leaf tips become withered. Margins have rolled under and the leaves are twisting, spiraling and are very brittle. The margins of the mature leaves are brown on the middle of the leaf and progress toward the tip; they are also rolling under and withered.

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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