Common Tomato Problems. Reasons Phosphorus deficiency. Leaves with P deficiency are usually dark green to bluish green in color. Potassium (K): vital for flower and fruit growth. This phenomenon has occurred with almost every tomato variety, and some other non-tomato plants, that I have grown in my passive wick Hydrosock Plain 2 Grow System. Reasons Phosphorus deficiency Leaves with P deficiency are usually dark green to bluish green in color. The bottom leaves show interveinal chloroses and necrotic leaflets. Reasons Phosphorus deficiency Leaves with P deficiency are usually dark green to bluish green in color. Phosphorus deficiencies (Figure 1) occur early in the growing season when soil is still cool. As the deficiency worsens, the purple color becomes more noticeable. TOMATO STEM Calcium deficiency Death of growing point and die-back of main stem from tip; die-back of leaves, progressing from terminal leaflets and of flower and fruiting trusses. This lovely purple tint is a classic symptom of phosphorus deficiency in a tomato seedling. Growth is sparse, thus the plant shows a spindly appearence. Total height is almost normal. Leaf edges showing potassium deficiency. Magnesium deficiency on tomato leaf. Exposure to intense light can also cause purple leaves on tomato plants. Phosphorus deficient plants develop very slowly. Growth is sparse, thus the plant shows a spindly appearence. Some leaves may be affected by all three mineral deficiencies at the same time! Tomato Plant Leaves and Nutrient Deficiencies. Phosphorus deficiency causes small and rigid leaves, the plant habitus is very erect. Don’t plant tomatoes too early in the season. ... Classic symptoms of calcium deficiency include blossom-end rot of tomato. Growth is sparse, thus the plant shows a spindly appearence. Phosphorous. Phosphorous is one of the three primary nutrients required by plants in relatively large quantities and is essential for cell division, strong stems, and good root development. The bottom leaves show interveinal chloroses and necrotic leaflets. Plants develop a distinct purpling of the stem, petiole and the under sides of the leaves. Use plastic mulch to warm the soil. TOMATO PLANT Phosphorus deficiency Growth dwarfed and thin; leaflets droop, curl backward and develop strong, dull purple tints. Total height is almost normal. The bottom leaves show interveinal chloroses and necrotic leaflets. Phosphorus deficiency causes small and rigid leaves, the plant habitus is very erect. Phosphorus is abundant in our soils but may be unavailable to the plant when the soil is too cold. There are also pests and diseases that can cause leaves to turn purple. 252. Phosphorus deficiency causes small and rigid leaves, the plant habitus is very erect. Phosphorus (P): essential for healthy roots and also for fruit to ripen. Purple leaves usually indicate phosphorus deficiency. A phosphorus deficiency will cause the leaves on a tomato plant to turn purple, especially if the plant is young or if temperatures are low (below 60 degrees Fahrenheit). Lack of phosphorus shows up when growth is poor, leaves begin to have a blue/green tint or fall off and fruit and flowers are disappointingly small or late. Many times, there is plenty of phosphorus in the soil, but the plant can't get to it. When I was new at this, the sight greatly perturbed me. 253. As a soil grower, I knew that purple under leaves and veins on plants meant either a phosphorus deficiency or a disease. Under severe deficiency conditions there is a tendency for leaves to develop a blue-gray luster. Total height is almost normal.