I have a number of box bushes in pots in my garden which have been there for many years. I have noticed this year that the leaves on some of them are looking quite yellow, not the glossy green that they should look like. Why is this, what should I do about it and at what time of year should I do it? Thanks

Angela, October 2007

It sounds like you may have been sleepwalking and painting the leaves yellow, check your tool shed for missing yellow paint and the tell tale signs of yellow fingers and a turps smell first thing in the morning. May i also suggest a padlock for the toolshed door.

Alan Titchmarsh, February 2008

There can be many different reasons for this. I just took a class on this and it can be potassium, nitrogen, or phosphorus deficiency. I do not have the specifics with me right now, but depending on which leaves are yellow you can tell which one your plant is low on. I'm pretty sure if the yellow leaves are on top than it is short in nitrogen because nitrogen can spread in your plant. When you go buy a fertilizer it goes N-P-K (nitrogen, phosphorus, and potassium) The number on the bag tells you how much of each nutrient is in the fertilizer. When you go buy fertilizer be sure you get the one with most nitrogen, because soils usually have high potassium already and phosphorus is immobile, which means it doesn't move easily through the soil. To get more phosphorus you would have to dig down to the root and put phosphorus in. Hopefully this helped some people, sorry i couldn't add more detail my notes are back at college, and I am home for winter break.

Brian, December 2007

From my experience, pot plants will eventually begin to turn yelllow when they have used up all the nutrients available in the soil. If they are evergreen plants you could try giving them about a 1/2 dose of plant food/fertilizer from any garden centre now. Small dark brown/black patches within the yellow areas would be a sign of a phosphorus deficiency which the plant food will fix. A full strength dose could cause a shock to the plants and possibly kill them so a 1/2 strength dose now and seeing is there any improvement over 1-2 weeks might help before going full strength. If the plants are due to lose their leaves in winter then you would be better off to wait until the first shoots return in spring and dose them the same as for evergreen.
Hope this is of some help to you.

Brian, November 2007