I have a client that has 20-25 4-6' Foster Holly trees. (I didn't plant) They are at best ok down to almost dead. They have had almost NO gowth since planting 4-5 YEARS ago. He is concerned that the wash off from the concrete slab directly in from of them is affecting them. Apparently there is a chemical in concrete that is bad?????? He has since installed slate over the concrete. Here are my questions.. could concrete have hurt them?? If so, can it be undone?? HOW??? IF not, what can I do to try to heal them....ie. fertilizer, deep root fert, WHAT????? THANKS FOR ALL YOUR HELP IN ADVANCE!!!!!!!!!!!!!!!
Not familiar with Foster Holly, but if they are in the same family as Princess or China Holly, then yes, your client is correct. Hollies require acidic soil and the nearby concrete is leaching calcium into the soil, causing a life threatening alkaline condition. Do a soil test to find out the ph and correct it with aluminum sulfate. 1# of aluminum sulfate/100 sf will reduce the ph approx. 0.2 units. Hollies like ph of 4.5 - 5.0.
They need fertilizer. Do a soil test around the ones near the concrete and another soil test away from the concrete. Then you will see what nutrients are lacking and pH levels need correcting.
I wonder if that's what has been wrong with my Japanese Boxwoods all this time. I used crushed limestone as the mulching material. They were planted in summer of 1998 and they have never done well. Only a few have grown enough to trim once a year and most are only a few inches taller than they were when planted. I've always assumed it was the heat from the rocks that was causing them to do poorly. But I'm now thinking the wash off from the limestone was too basic or acidic and moved the soil pH to a range that the plants don't like. Isn't crushed limestone a big ingredient in concrete? I'm ordering a soil pH tester from Gemplers today. pH can just cause too many problems for too many plants if it's not in an acceptable range. Later, DFW Area Landscaper
Crushed limestone will act almost like the lime you apply in your turf areas. Its raising the pH level around those boxwoods. Thats the main reason i use all wood barks around shrubs.
Although the PH may be a problem, no growth indicates another problem. They were most likely planted too deep and may have girdling roots. http://www.upenn.edu/paflora/plantclinic/damagedroots.htm Often, an experienced arborist can identify girdling roots from an above ground visual inspection. Once girdling is suspected, a below ground inspection is needed to assess the extent of damage. Where possible, removal of the girdled roots can often extend the useful life of the tree. Young trees may require another inspection after several seasons to remove any girdled roots that have redeveloped. A Certified Arborist should look at the trees before any action is taken. http://www.isa-arbor.com/findArborist/findarborist.asp
