Zucchini Growing Guide

Which leaves: Young/new growth first

Symptoms: In developing fruit: dark brown-black, sunken, leathery patch at the blossom end of tomato, capsicum, eggplant, zucchini fruit (blossom end rot). In leaves: new growth is distorted, small, and cupped or hooked downward. Brown spots appear on young leaves and leaf tips. Tip burn on lettuce inner leaves is a classic calcium deficiency symptom.

Fix: Maintain consistent soil moisture with deep, regular watering and thick mulch. Apply liquid calcium products (eco-flo lime, liquid gypsum). Gypsum adds calcium without altering pH. Remove affected fruit so plant redirects resources.

Often confused with: Fungal disease (blossom end rot is not infectious); Boron deficiency (similar distorted new growth); Magnesium deficiency (but Mg affects old leaves); Sunscald on fruit

Which leaves: Young/new growth and growing tips first

Symptoms: Growing tips die back; new leaves are small, thick, brittle, and leathery. Leaves at the tip may show yellowing edges or rust-coloured patches. Stems and petioles may crack or feel brittle. Hollow stems in broccoli and cauliflower; rotting or brown heart in beetroot and turnip; cracked stems in celery; small deformed heads in cauliflower; leaf tip dieback in lettuce.

Fix: Apply borax at very low rates - 0.5g per square metre as a soil drench (caution: very narrow margin between deficiency correction and toxicity). Lower soil pH if above 7.0. Seaweed extract contains some boron.

Often confused with: Calcium deficiency (both cause distorted new growth and browning of tips and hearts); Drought stress; Fungal disease in brassica hearts; Hollow stem in broccoli from rapid growth

Which leaves: Old/lower leaves first

Symptoms: Uniform pale yellowing (chlorosis) starting on lower leaves and spreading upward. Entire plant looks washed out and light green. Stems may be thin and spindly. Older leaves may develop pinkish or reddish tints before dropping. Fruit and foliage are smaller than normal. Growth is slow and stunted.

Fix: Apply blood and bone meal or poultry manure pellets immediately. Liquid fish emulsion or worm castings tea gives faster results. For containers, use a liquid fertiliser with nitrogen fortnightly.

Often confused with: Winter cold or waterlogging; Root damage from nematodes or fungal pathogens; Sulphur deficiency (but sulphur affects new growth first); General overwatering

Which leaves: Old/mature leaves first

Symptoms: Scorched or burnt-looking leaf edges (marginal leaf scorch) starting at the tips, progressing inward. Older leaves turn yellow then brown at the margins. Leaves may curl, crinkle, or roll along the edges. Fruit is small and poorly coloured. Plants are more susceptible to drought and frost. In tomatoes, fruit may ripen unevenly.

Fix: Apply comfrey leaves as mulch (extremely high potassium). Make comfrey liquid fertiliser. Wood ash is a fast-acting organic source but raises pH. Seaweed meal or liquid seaweed provides potassium.

Often confused with: Drought stress or heat scorch (similar marginal leaf burn); Salt damage from over-fertilising; Magnesium deficiency (but Mg shows interveinal yellowing, not marginal scorch); Sucking insect damage

Which leaves: Old/lower leaves first

Symptoms: Interveinal chlorosis (yellowing between the veins while the veins themselves stay green) on older leaves. Leaves look like a green fishbone pattern on a yellow background. Reddish-brown or purple tints may appear between veins in advanced cases. Older leaves drop prematurely. In tomatoes, the lower leaves yellow first and progressively up the plant.

Fix: Foliar spray of Epsom salts (magnesium sulphate) at 20g per litre of water, applied fortnightly. Soil drench of Epsom salts is slower but effective. Apply dolomite lime to acidic soils. Stop high-potassium feeds if overuse is the cause.

Often confused with: Iron deficiency (but iron affects NEW leaves, not old leaves); Manganese deficiency (affects young leaves); Normal autumn leaf yellowing; Nitrogen deficiency (nitrogen causes uniform yellowing, not interveinal)

Which leaves: Young/new growth first

Symptoms: Interveinal chlorosis on youngest leaves, which turn pale yellow to almost white while leaf veins remain distinctly green. Most visually striking deficiency in the garden. In severe cases, entire new leaves turn white. Growth slows and new leaves may be stunted. Brown dead spots can appear between veins in severe cases.

Fix: Apply chelated iron as soil drench or foliar spray for rapid correction. Lower soil pH with sulphur powder. Liquid seaweed extract contains natural chelating agents. Add sulphur or acidic compost around affected plants.

Often confused with: Manganese deficiency (very similar; manganese shows on young-to-middle leaves); Zinc deficiency (also affects new leaves but causes small leaves and rosetting); Sulphur deficiency (uniform yellowing, not interveinal)

Which leaves: Young/new growth first

Symptoms: New leaves are abnormally small and may be pale green or yellow between the veins. The gaps between nodes become very short, giving a rosette or clustered appearance. Leaves may be narrow and distorted. Brown or bronze spots appear on leaf margins and tips. Shoot tips are stunted. Multiple small leaves cluster at the growing tip (little leaf or rosetting).

Fix: Foliar spray with zinc-containing seaweed or micronutrient fertiliser. Add organic compost. Lower soil pH with sulphur if alkalinity is the cause. Apply rock dust or kelp meal as a slow release source.

Often confused with: Boron deficiency (also causes small deformed new leaves and rosetting); Iron deficiency (interveinal chlorosis on new leaves, but zinc has distinctive small leaf size); Virus infection (mosaic patterns can look similar)

Which leaves: Young to middle leaves

Symptoms: Interveinal chlorosis (pale yellow tissue between green veins) on young to middle leaves. Similar to iron and magnesium deficiency but affects upper-to-middle leaves. Tan or sunken necrotic spots may appear in the chlorotic zones. Leaf margins may brown. In severe cases, leaves die and drop.

Fix: Apply manganese sulphate as a foliar spray for rapid correction. Liquid seaweed contains some manganese. Lower soil pH with elemental sulphur. Improve drainage. Add composted seaweed or greensand rock dust.

Often confused with: Iron deficiency (very similar; iron is strictly on newest tip leaves, manganese on slightly older young leaves); Magnesium deficiency (but Mg affects old leaves); Zinc deficiency (zinc shows rosetting and smaller leaf size); Mite or insect damage

Which leaves: Older/lower leaves in most vegetables; developing leaves progressively in brassicas

Symptoms: In brassicas: classic whiptail symptom where leaves become narrow, strap-like, and twisted. The leaf blade does not develop properly, leaving only the midrib or a thin strip of leaf tissue. Head formation is inhibited. In legumes and other vegetables: older leaves show faint yellow-green chlorosis with marginal browning. In lettuce and cucurbits: whitish-tan interveinal chlorosis with marginal leaf burn.

Fix: Lime the soil to raise pH above 6.3 - this alone often resolves the deficiency. Apply fritted trace elements that include molybdenum. A foliar spray of sodium molybdate at very low dilution for immediate correction.

Often confused with: Fungal or viral disease causing leaf distortion in brassicas; Nitrogen deficiency (similar chlorosis); Herbicide damage causing leaf distortion; Cabbage aphid damage causing distorted cupped leaves

Which leaves: Old/lower leaves first

Symptoms: Stunted, slow-growing plants with small, dark green leaves. Older leaves develop a reddish-purple or bronze discolouration, most visible on the undersides and along leaf veins. Stems become thin and spindly. Fruit set is poor. In tomato seedlings, the entire plant turns purple underneath when soil is cold.

Fix: Apply blood and bone or bone meal worked into the soil. Rock phosphate is a slow organic source. Raising soil temperature with black plastic mulch will often resolve cold-related purple colouring in seedlings.

Often confused with: Cold stress (purple seedlings from cold soil mimic phosphorus deficiency); Anthocyanin pigmentation in some varieties (normal); Early fungal disease

Which leaves: Young/new growth first

Symptoms: Uniform pale yellowing of new leaves and growing shoots while older leaves remain green. Entire new leaves turn light green to yellow, not just between veins. Stems are thin, short, and spindly. Petioles and stems may show reddish-purple colouration in tomatoes and potatoes. Growth is slowed. In peas, young leaves curl inward.

Fix: Apply gypsum (calcium sulphate) to soil as a sulphur source that does not alter pH. Epsom salts (magnesium sulphate) adds both sulphur and magnesium. Blood and bone and aged manures contain organic sulphur.

Often confused with: Nitrogen deficiency (most common confusion; nitrogen affects OLD leaves, sulphur affects NEW leaves); Iron deficiency (also affects new leaves; but iron shows interveinal pattern, sulphur is uniform yellowing)

Which leaves: Young/new growth first

Symptoms: Young leaves wilt without going yellow first, then turn pale green and begin to curl downward. Tips and upper leaf surfaces develop a distinctive blue-green colouration. Leaves appear limp and lifeless even with adequate water. Growing tips may die back. Onions and leeks may show collapsed, pale leaf tips.

Fix: Apply copper sulphate to soil at low rates (copper is toxic to earthworms at high doses). Poultry manure contains copper. Amino-copper chelates are a gentler option. Lower soil pH if alkalinity is the cause.

Often confused with: Drought stress or heat stress (wilting young leaves looks like underwatering); Root disease causing wilting; Iron or manganese deficiency (interveinal chlorosis in later stages)