[Cristina]

Cristina asked the Naked Scientists:
   
Hi, I'm Cristina from Spain.

I have a plant in my terrace, in Madrid. (in case it was important, the terrace in glazed). Some of the plant leaves are yellow, brown...almost dying.

I thought it wasn't doing photosynthesis properly, so as far as I remember,  the product from photosynthesis is starch.

To help the plant, I have started leaving some sugar in the earth of the plant pot.

However, I don't dare to leave too much sugar.

Do you think this thing of  leaving some sugar in the earth plant pot,  can help the plant  to recover the green colour of its leaves??

Thank you in advance!!

Cristina

What do you think?

[nickki33flem]

Adding sugar to soil will work, it consist complex carbohydrates and plants do need it. Green plants use this sugar to make starch, proteins and fats. But instead of adding sugar directly, you can add sugar dissolved in water to your plants, so that soil can absorb it in better manner. Hope this will help you Cristina.

[Don_1]

What are you growing? Different plants have different requirements.

One of the most common causes of yellowing leaves is over watering, but this will often depend on the plant. Pelargoniums and marigolds are among those plants which do not like being over watered and will show yellowing of the leaves if the are.

A lack of nitrogen, iron or manganese could also be your problem, or having acid loving plants in an alkaline soil. The soil/compost in your tubs may have become exhausted.

While the addition of sugar may, and I stress may, help put some nutrition back into the soil, it is more likely to simply attract unwanted insects into your pots such as ants, which can undermine the soil's structure.

If you are growing annual bedding plants, I would suggest you discard them, renew the compost and replant with fresh young plants. If you have perennials, you might find it best to take cuttings and start again with fresh compost. In the case of evergreens and deciduous shrubs, it may well be that they have exhausted the compost to a point where it can no longer be replenished. Again I would suggest taking cuttings or replacing them.

Personally, I would not recommend using sugar, it sounds more like a water, acidity or lack of nitrogen problem to me.

If you are growing flowering plants, overdoing the nitrogen can result in masses of leaves and few flowers. Your best option on fertiliser is one of the balanced proprietary plant foods with nitrogen, potassium and phosphorous.

Make sure you use the correct compost. A general compost is fine for bedding plants, but a soil based compost, such as John Innes No. 3, is best for long term planting and an ericacious compost for most evergreens and shrubs. Also, in the case of evergreens, shrubs and other acid loving plants, be sure not to use tap water, as it will be alkaline and would eventually alter the Ph of the soil.

[Bored chemist]

I suspect that adding sugar (with or without water) to the soil would mainly feed the soil bacteria.

[PaulFlores101]

Hmm! i've never heard about adding sugar to help crop grow healthier. What can we do about the ants. Plus, sugar contains mostly carbon and too much of this will only slow things down. So if you're going to make organic compost then you should look for common source like bone meal or blood meal. Cheers

[Bigjoemonger]

Don't just put sugar. Plants have complex nutritional requirements just like animals.

Try chopping up some banana peels and mixing it into the soil.

[smart]

Adding sucrose to your soil medium will strongly inhibit plant growth while in the vegetative state. To improve your soil medium, stick to the basic and just add a fertilizer with balanced nitrogen/phosphorus/potassium ratio. You might also want to experiment with compost while you are at it...

See: https://en.wikipedia.org/wiki/Compost
 

[Colin2B]

Adding sucrose to your soil medium will strongly inhibit plant growth while in the vegetative state.

A study published in the Journal of Vegetation Science, shows it does. The researchers added sugar every year to a hay meadow. After 10 years the weight of vegetation was lower and the amount of bare ground greater in plots treated with sugar than in control plots.
What is really interesting is why. Apparently the sugar gives soil microbes a shot in the arm, so they grow faster and compete more effectively with the plants for nutrients. The total amount of soil nutrients doesn’t change, but there is less for the plants, so these grow more slowly and biomass goes down.

So, @Bored chemist you were right