Old hat, zone 4, cold climate garden blog.

About a week ago I was working in the greenhouse when I noticed some of the regal geraniums had yellowing leaves.

My first thought was Botrytis, which is a blight that can be easily controlled with a fungicide.  We use a product called Serenade to control any fungus in the greenhouse because it is organic and will not kill us.  For more info or to find a store go to their website at www.serenadegarden.com

After looking at some images on the web I was concerned that this might be a bacterial infection like Ralstonia solanacearum or Xanthomonas campestris so we called our Cornell Cooperative Agent and she came by and picked up a plant to send down to the Cronell lab to be checked out.

I picked a few leaves to hand her and she said she needed a complete plant, holding a 6″ by 6″ box open.  Hmmm, most of the plants are much larger than that but after some looking we found a small 3 inch pot with a scented geranium with some yellow leaves.

She sent the plant off and advised me that it would be a few days before we knew what was what.

If the problem turned out to be Ralstonia or Xanthomonas we would need to destroy all the plants.

In the mean time our state inspector, who I had called also, stopped by to take a look.

He thought that the problem was more of water uptake than anything else.   Some of the plants were root bound and we knew this as we were in the process of re-potting all of the plants.

Sure enough the lab agreed and we gave a sigh of relief.

Now we can get back to re-potting the root bound plants.

When plants are kept for a time in a confined space the roots grow in circles  and the soil is taken up and washed away.  After a while it is almost impossible to water the plants because there is no soil to hold the water.  Most of it pours right through the roots on to the greenhouse floor.

In addition to that the roots become covered with salts from the water and feeding and this makes it even harder for the plant to take up water and nutients.  New roots are nice and white and fuzzy while old roots are course, brown and stringy.

We break all the soil from the roots and pull a good deal of the dead roots loose.  The idea is to pot the plant up in a larger container but we also want to loosen the roots up so they do not continue to grow in a circle.

After potting up in fresher soil we keep them in the shade for a few days and make sure they are well watered but not soaked.  In a few weeks new roots will be exploding and the whole plant will look and be better for it.