Iron or manganese2
New broadleaf foliage is undersized and yellow to whitish, except for green along the veins when iron or manganese or both are deficient. Brown dead spots may develop at margins, tips, and between veins. Conifers’ upper canopy and palms’ newer fronds become yellow while lower foliage appears normal. Iron and manganese deficiency are common in plants growing in sandy soils and in species adapted to acidic soil that are grown in high-pH (alkaline) soil.
Magnesium
This deficiency is common in palms, especially date palms, and rare in landscape broadleaf plants and conifers. In magnesium-deficient palms leaf tips and terminals turn bright yellow, while leaf bases and along the midrib remain green. Lower (older) fronds may die prematurely when magnesium is deficient. In magnesium-deficient broadleaf plants, foliage can become chlorotic or both chlorotic and necrotic.
Nitrogen
Older leaves or needles become uniformly pale green to yellowish when nitrogen is deficient. New growth is sparse and undersized but is usually green. Plants grow slowly and may drop foliage prematurely. Palms develop color gradation with the oldest fronds becoming the most chlorotic and sometimes turning completely yellow or whitish.
Phosphorus
The young foliage of broadleaf plants becomes abnormally dark green when phosphorus is deficient. Leaves overall or veins only may be purplish, especially on leaves' underside. Conifers’ older needles become dull colored or gray green and drop prematurely. Phosphorus deficiency is rare in landscapes except where topsoil has been removed such as during development.
Potassium
Foliage growth is sparse when potassium is deficient. Older broadleaf foliage is yellowish or brown at the tips and margins and between veins. Leaf edges crinkle or curl. Conifer needles become dark blue-green, yellow, or brown and undersized with dead tips. Older palm fronds have yellow, orange, or brown in flecks or spots or along margins, tips, and midribs. Potassium deficiency is rare in California landscapes except in container plants, fruit and nut trees grown in sandy soils, and palms.
Zinc2
Broadleaf foliage becomes uniformly yellowish or pale between the veins, especially on new growth when zinc is deficient. Spring leaf flush and blossoming may be delayed. New leaves may be narrow, undersized, and growing in tufts. Older leaves may drop prematurely. Conifer needles are yellowish and undersized and may drop prematurely. Sandy soils commonly lack sufficient zinc.
1. Deficiency symptoms commonly result from adverse soil conditions and anything that makes roots unhealthy. These include conditions favoring salt damage to plants, pH problems, or salinity, or salt toxicity. Conditions that injure roots include aeration deficit (waterlogging), soil-dwelling nematodes, poor irrigation practices, and root decay pathogens). Hardpan soil layers and insufficient soil volume also inhibit plants' nutrient uptake. Note that nutrient excess can also damage plants, including excess nitrogen and boron and other specific ions. Nutrient availability to plants also varies according to soil pH. Soil pH of 6 to 7.5 is best for the growth of most plants.
2. Micronutrient deficiency symptoms especially are generally not due to insufficient nutrients in soil.
