Yellow Leaves on My Roses - Part 2


Other symptoms to look for:

  • Sometimes purple discoloration on the leaves.
  • Lower leaves may fall prematurely from the plant.
  • Older leaves may have a mottled appearance.
Treatments:
  • Perform a soil test; correct soil pH to 7.0 or lower.
  • In magnesium-deficient soils, add fish meal, basic slag, greensand or dolomitic limestone, or
  • Add Epsom salt (magnesium sulfate).
Nitrogen deficiency

Nitrogen stimulates growth of the rose's canes, dark green foliage and good blooms. A lack of nitrogen manifests as small, light green leaves. On roses with yellow blooms, a lack of nitrogen frequently appears as yellow leaves. Nitrogen availability occurs in most soils with a pH above 4.5.

Other symptoms to look for:

  • Weak, spindly stems.
  • Small flowers.
Treatments:
  • Perform a soil test; correct as necessary.
  • If nitrogen is deficient, add blood meal, cottonseed meal and/or manure for organic amendments, or
  • Add nitrate of soda or ammonia sulfate for inorganic amendments.
Sulfur deficiency

Sulfur is the building block of amino acids and proteins (protoplasm) necessary for plant health. It promotes strong root development. Sulfur deficient soils produce rose leaves with both yellowish leaves and veins. Generally, these appear near the top of the plant on newer growth. It is widely available is soils with a pH above 4.5.

Other symptoms to look for:

  • None.
Treatments:
  • Perform a soil test; correct as necessary.
  • Add sulfur, ammonium sulfate and/or potassium sulfate as necessary. Use caution when applying sulfur compounds, however. Too much sulfur ("sulfur toxicity") appears as veinal chlorosis followed by rapid defoliation of the lower leaves.

Manganese deficiency

Manganese, like magnesium, aids in the production of chlorophyll and activates enzymes to assist the photosynthetic process. A lack of manganese looks very similar to magnesium deficiency except that the smallest leaf ribs ("veins") remain green and take on a spider web or netted appearance. Manganese is generally available in soils with a pH below 7.0, but resumes its availability is soils above 8.5.

Other symptoms to look for:

  • Pale spots on new foliage.
  • Mottled older leaves
  • Symptoms appear mainly on new growth near the top of the plant.

Treatments:

  • Perform a soil pH test; correct to 6.5 or lower.
  • In deficient soils, add millorganite or houorganite treated sludge organic amendments, or
  • Add manganese sulfate inorganic amendments.

Nutrient toxicity

Zinc toxicity

Although it is rare, too much zinc can cause symptoms similar to iron or magnesium chlorosis. That is, the leaf tissues first turn yellow, then turn brown. The main leaf rib remains green, but the secondary veins lighten. New growth may become stunted and bloom

The copyright of the article Yellow Leaves on My Roses - Part 2 in Rose Gardening is owned by Mark Whitelaw. Permission to republish Yellow Leaves on My Roses - Part 2 in print or online must be granted by the author in writing.

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