News
If Leaves Turn Yellow
The Summer heat, together with some degree of malnutrition can be fatal to your plants. This is when the leaves start to turn yellow.
Known as chlorosis, the yellowing of plants' leaves can point to a variety of health problems. In general, it's the visible result of too little chlorophyll, the pigment used by plants to trap sunlight for photosynthesis. Since chlorophyll gives leaves their green color, an inadequate supply turns plants a pale green, yellow or yellowish white. And since chlorophyll is key to plants' food-making abilities, a plant suffering from chlorosis might not survive if the source of its chlorophyll shortage isn't addressed.
One common reason for chlorosis is poor nutrition. Beyond hydrogen, carbon and oxygen, plants need more than a dozen mineral nutrient to survive, all of which must come through their roots. A soil test is the best way to know what's missing, but a quick look at the leaves can shed light on the situation. Plants with nutrient deficiencies often have distinct patterns of chlorosis, like green veins with yellow tissue in between, that first appear on particular leaves.
Some nutrient deficiencies make older leaves turn yellow first; others start with new growth. That's because certain nutrients are "mobile" in plants, meaning a plant can move them from leaf to leaf as needed. When a plant runs low on a mobile nutrient like nitrogen, it can take more from its older leaves, helping the plant continue growing (at least for a while). Loss of nitrogen turns the older leaves yellow, while new growth comes in green. An immobile nutrient like iron, however, is essentially stuck in older leaves. If a plant runs out of iron, it will develop chlorosis in new leaves while earlier foliage stays green.
Aside from nitrogen, mobile plant nutrients include phosphorus, potassium, magnesium and nickel. Iron is joined in the immobile category by calcium, sulfur, boron, copper, manganese and zinc.
Once you've narrowed down the suspects to mobile or immobile nutrients, look for more clues in the way a leaf is turning yellow. Nitrogen and potassium deficiencies both appear in older leaves, for example, but while nitrogen chlorosis is relatively uniform across the leaf and its veins, potassium chlorosis tends to start on leaf edges and spaces between veins. Yellowing of new leaves could point to iron or calcium, but iron chlorosis is characterised by uniform yellowing with small, green veins.
The solution is to recur to a good fertiliser, taking care to follow the instructions without overdoing with the dosage.
Known as chlorosis, the yellowing of plants' leaves can point to a variety of health problems. In general, it's the visible result of too little chlorophyll, the pigment used by plants to trap sunlight for photosynthesis. Since chlorophyll gives leaves their green color, an inadequate supply turns plants a pale green, yellow or yellowish white. And since chlorophyll is key to plants' food-making abilities, a plant suffering from chlorosis might not survive if the source of its chlorophyll shortage isn't addressed.
One common reason for chlorosis is poor nutrition. Beyond hydrogen, carbon and oxygen, plants need more than a dozen mineral nutrient to survive, all of which must come through their roots. A soil test is the best way to know what's missing, but a quick look at the leaves can shed light on the situation. Plants with nutrient deficiencies often have distinct patterns of chlorosis, like green veins with yellow tissue in between, that first appear on particular leaves.
Some nutrient deficiencies make older leaves turn yellow first; others start with new growth. That's because certain nutrients are "mobile" in plants, meaning a plant can move them from leaf to leaf as needed. When a plant runs low on a mobile nutrient like nitrogen, it can take more from its older leaves, helping the plant continue growing (at least for a while). Loss of nitrogen turns the older leaves yellow, while new growth comes in green. An immobile nutrient like iron, however, is essentially stuck in older leaves. If a plant runs out of iron, it will develop chlorosis in new leaves while earlier foliage stays green.
Aside from nitrogen, mobile plant nutrients include phosphorus, potassium, magnesium and nickel. Iron is joined in the immobile category by calcium, sulfur, boron, copper, manganese and zinc.
Once you've narrowed down the suspects to mobile or immobile nutrients, look for more clues in the way a leaf is turning yellow. Nitrogen and potassium deficiencies both appear in older leaves, for example, but while nitrogen chlorosis is relatively uniform across the leaf and its veins, potassium chlorosis tends to start on leaf edges and spaces between veins. Yellowing of new leaves could point to iron or calcium, but iron chlorosis is characterised by uniform yellowing with small, green veins.
The solution is to recur to a good fertiliser, taking care to follow the instructions without overdoing with the dosage.