Nutrient deficiencies of perennials: Part 11 of 12

Phlox carolina

Phlox carolina is one of the upright group of phlox and an outstanding garden perennial hardy to USDA Hardiness Zone 3. The bloom time of this North American native is slightly earlier than the better-known Phlox paniculata, and is also more resistant to powdery mildew. P. carolina ‘Miss Lingard’ has clean white flowers atop 2- to 3-foot-tall stems. Deadheading will result in rebloom later during the summer.

Researchers at Virginia Tech induced and documented deficiency symptoms in vegetatively propagated P. carolina ‘Miss Lingard’. We used a hydroponics system to completely exclude the desired element; this also afforded a great view of the root system.

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The best way to assure proper nutrient levels is to test rootzone pH and electrical conductivity on a regular basis; if deficiency symptoms appear, verify your diagnosis by sending foliar samples to an analytical laboratory.

Pictures related to the nutrient deficiencies series may accessed by viewing the PDF files of the pages that originally appeared in GMPRO magazine: Page 1. Page 2. Page 3. Page 4. Page 5. Page 6.

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Nitrogen (N)

Initially, nitrogen-deficiency symptoms are exhibited in both young and recently mature leaves being lighter green and slightly chlorotic.

As symptoms progress, purple and yellow discolorations occur on older leaves along with necrotic spots on leaf edges. Younger leaves become highly chlorotic, with red and necrotic spots. Growth is stunted, stems are smaller in diameter and flower buds are not produced.

Phosphorus (P)

Within two weeks, phosphorus-deficient plants exhibit an increase in internodal growth.

Recently mature leaves curl and younger foliage is thinner and smaller compared to the control.

After six weeks, plants are lighter green, with smaller leaves and fewer flowers and buds at each node.

Potassium (K)

Two weeks after potassium exclusion, recently mature and older leaves show interveinal chlorosis with purple discolorations and burned tips. Roots are highly branching with short, knobby lateral roots.

As potassium-deficiency progresses, chlorosis increases and necrotic spots appear on leaf tips and margins. Roots have fishbone appearance with black discolorations.

Calcium (Ca)

Within a week after excluding calcium, recently mature leaves show slight chlorosis on edges and tips. In addition, roots are dark brown with minimal growth.

Calcium-deficient plants quickly decrease in growth, with shorter internodes and roots become necrotic. Young and recently mature leaves have yellow edges with necrotic spots. Eventually, necrotic spots progress into the center of leaves until they become completely necrotic.

Magnesium (Mg)

Magnesium-deficiency symptoms begin with chlorosis on young and recently mature leaves beginning at the leaf base and progressing to the tip, while older leaves have chlorotic edges.

Marginal leaf chlorosis increases and growth is stunted with stems, internodes and roots shorter than the control. Additionally, older leaves feel thick and leathery to the touch, with reddish-brown spots on leaves and edges.

Sulfur (S)

Initially, sulfur-deficient plants exhibit slight chlorosis on young and recently mature leaves beginning at the base of the leaves progressing to tips.

As symptoms progress, leaves are smaller and thinner than the control and chlorotic with necrotic spots. Older leaves appear to be darker green; spots on the stems are a deeper reddish hue compared to the control.

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Boron (B)

Two weeks after excluding boron, young and recently mature leaves are slightly chlorotic while older leaves begin cupping.

Roots have fishbone appearance with greenish tint and brown root tips.

Leaf cupping increases in boron-deficient plants and root growth is stunted while roots turn brown.

Copper (Cu)

Fourteen days after excluding copper, recently mature leaves begin curling with slight chlorotic tips and margins. Older leaves begin to turn yellow and brown while newer foliage and flower buds become twisted and distorted with necrotic spots.

Iron (Fe)

Within one week after excluding iron, interveinal chlorosis appears on younger leaves, then progressing to older leaves.

Roots are thin, orange and stunted with dark-orange root tips.

Iron-deficient plants quickly become highly chlorotic and the newest leaves are almost white with necrotic spots.

Manganese (Mn)

Initially, manganese-deficiency symptoms appear as slight chlorosis on young and recently mature leaves. Older leaves begin cupping, with interveinal darkening combined with dark-green mosaic discolorations.

As manganese deficiency progresses, leaf chlorosis increases and older leaves exhibit leathery, drooping leaves with necrotic spots.

Zinc (Zn)

Zinc-deficiency symptoms begin with curling, small, lime-green young and recently mature leaves.

Within four weeks, plants exhibit “shepherd’s crook” and “little leaf syndrome” typical of zinc-deficiencies. Young and recently mature leaves are chlorotic with red margins and necrotic spots. Root and shoot growth are stunted, with stems also having necrotic spots.

- Jaime L. Crocker, John R. Freeborn and Holly L. Scoggins

Holly Scoggins is associate professor, Jaime L. Crocker is graduate research assistant and John R. Freeborn is research technician, Virginia Tech, Department of Horticulture, (540) 231-5783; perennials@vt.edu.

The authors thank Fred C. Gloeckner Foundation for grant support, Yoder-Greenleaf for plant material and Quality Analytical Laboratories for tissue analysis. The authors thank Virginia Tech metabolomics specialist Joel Shuman for technical assistance, and partners in the study, University of Florida assistant professor James Gibson and his staff and students at West Florida Research and Education Center in Milton , Fla.

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