Curling crumbling leaves

I use six 40-watt tubes in a two by four shelf. I use a soil mix with a pH of 6.8 and use half-strength fertilizer every time I water.
I ran into problems with my last crop. The clones and seeds started fine, but when they were 10-12 inches high after four to six weeks, they started getting upward leaf curl and browning of the leaf tips, which then started drying and crumbling. Some remained green but also got this upward curl and crumble. The condition started right below the new growth and spread to the rest of the plant. What was happening?

Perplexed,
Ohio

The plants are dying from over-fertilization. At some point the nutrients in the soil mix became so concentrated that they began to draw water from the plant, leaving the leaves curled and dry.

To solve the problem, flood the soil to dissolve water-soluble salts and drain them from the container. Flood a two-gallon container to at least a gallon of water drain. The drained water can be diluted and used to water outdoor plants. Residual nutrient salts remain in the planting mix. The plants will use these so you can stop fertilizing. Restart only when there is an indication that the plants need additional nutrients. In the future, supply the plants with only one-third to one-half the fertilizer they were previously receiving.

Readers with grow questions (or answers) should send them to Ed at: Ask Ed, PMB 147, 530 Divisadero St., San Francisco, California 94117, USA. You can also email Ed at [email protected], and send queries via his websites at www.ask-ed.net. All featured questions will be rewarded with a copy of Ed’s book, The Big Book of Buds. Sorry, Ed cannot send personal replies to your questions.

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