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rust spots on leaves during flowering

Magnesium deficiency guide

About magnesium in short

Symptoms of a deficiency

When there is a shortage, the leaf green in the medium-old leaves under the flowering top will be broken up, and the magnesium will be transported into the young parts of the plant. This breakdown is visible as rusty brown spots and/ or vague, cloudy, yellow spots between the veins. A slight shortage of magnesium hardly affects flowering, although the development of the flowers make the deficiency symptoms worse.

Development of a deficiency

  • Signs of a deficiency first appear around the 4th-6th week. Small, rusty brown spots and/or cloudy yellow flecks appear in the middle-aged leaves (under the top of the plant).
  • The color of the young leaves and the fruit development are not affected.
  • The size and number of rust-brown spots on the leaves increase.
  • The symptoms spread out over the whole plant, which looks ill. When the shortage becomes acute, the younger leaves are also affected and the flower production will be reduced.

Reasons for a deficiency

The magnesium deficiency can occur because uptake is inhibited because of:

  • A very wet, cold and/or acidic root environment.
  • A high quantity of potassium, ammonia and/or calcium (for instance high concentrations of calcium carbonate in drinking water, or clay potting mixes rich in calcium) in comparison with the quantity of magnesium.
  • A limited root system and heavy plant demands.
  • A high EC in the growing medium, which hinders evaporation.

Solutions to resolve a deficiency

  • When a shortage is diagnosed, the best thing to do is to spray with a 2% solution of Epsom salts.
  • Fertilization via the roots: Inorganic: Epsom salts on hydroponics or Kieserite (magnesium sulphate mono hydrate). Organic: composted turkey or cow manure.

Recovery

Rectify the possible causes: In potting mixes, when the pH is too low (less than 5), use magnesium containing calcium fertilizers. In hydro, temporarily apply a nutrient solution with a higher pH (6.5). When the EC is too high, rinse and/or temporarily feed with drinking water only.

When growing indoors, keep the root temperature between 20 – 25 degrees Celsius. A little extra magnesium is not particularly harmful. When growing in potting mixes, excessive quantities of magnesium do not appear quickly. Too much magnesium inhibits the uptake of calcium, and the plant displays general symptoms of an excess of salts; stunted growth, and dark-colored vegetation.

Magnesium deficiency guide – Magnesium is an indispensable element for plants. In plants, it represents a building block for chlorophyll (green leaves), and therefore, it is essential for photosynthesis.

Rust spots on leaves

GD1576
BigCube

It could be rust. But I assume it would have spread to the others by now if it was. If it was nutrient build up, you think flushing would have stopped it. Not made it worse.

I’d be leaning more toward a deficiency maybe, like low in calcium. Are you supplementing calmag?

Another option could be your water source. Maybe too much chlorine I the water, but not likely since the other plants are fine..

If you can help us out, let us know your particulars. Feeding schedule, nutrients used, supplementation used, rh, avg temps. Ect..

GD1576
NairnM16
NairnM16

It could be rust. But I assume it would have spread to the others by now if it was. If it was nutrient build up, you think flushing would have stopped it. Not made it worse.

I’d be leaning more toward a deficiency maybe, like low in calcium. Are you supplementing calmag?

Another option could be your water source. Maybe too much chlorine I the water, but not likely since the other plants are fine..

If you can help us out, let us know your particulars. Feeding schedule, nutrients used, supplementation used, rh, avg temps. Ect..

Hey guys 2nd grow and I obviously have a problem. These rust spots on my leaves, what are they? Initially I thought lock out, so I flushed for 3 days but…