Liming Rhododendrons - Part II
Alleyne R. Cook, Vancouver, B.C., Canada
Mr. Barbre's* description of the ordeal to which growing corn is subjected reminds me of a story told to me by a Park Ranger in the Smoky Mountain Park. He had married a girl from Honduras. There according to him they practice true democracy. Every year they shoot their President thus giving everyone a chance at that exalted position. It is probably necessary to watch the soil closely when the corn is growing for it is an annual crop and a greedy one.
*"More on Liming and Azaleas", A.R.S. Bulletin, October 1962.
If corn can be compared to the President of Honduras then a shrub in my estimation may be likened to the British Monarchy. Rather useless, certainly attractive, most convenient to have around, exceedingly durable and always in the best of health. And of all shrubs the rhododendrons are the ones most likely to give the greatest satisfaction for the least amount of trouble.
As far as I am concerned I don't care if the pH of my soil is 2 or 10 provided the shrubs I wish to grow are healthy. That is the only thing that matters and I suspect the only thing that interests most gardeners. If they are not healthy rather than use artificial fertilizer I prefer to use lime. If the plants look healthy and are growing well then why not leave them alone?
We know that the soil of this coast is acid. If this was not so we would not have the Ericaceae plants such as Gaultherias , Arbutus , Arctostaphylos , Cassiope , Phyllodoce , or the native rhododendrons growing here. So why worry what the pH is? What we do not know is what happens to the soil's acidity when anything is added to it. Regardless of whether that substance is lime or peat no one can say just what the new pH reading will be. Yet according to everyone if it is lime, even the lightest dusting, the soil will immediately become alkaline and all the plants will die. How stupid can that be?
Hemlock sawdust is nearly neutral, oak leaves are very acid, if either of these are used on a soil that is moderately acid the soil must change considerably. Peat is a very acid substance; before it can change from mulch and be of value as food it must have nitrogen. But in an acid soil this element is not available so that the addition of lime is the only way of correcting this. What is quite certain is that with few exceptions everything that is used to benefit the plants will be of greater acidity than the original soil and the elements needed by the plants will not be so readily available until some thing releases them. And that something is common agricultural lime. In New Zealand even though I worked for years with Ericaceous plants I never ever heard the term pH mentioned, nor in England. But in both these countries greater attention was paid to the fertility of the soil through digging in stable manures and mulching. As a result the land was in much better condition to receive and grow healthy plants. Yet as I pointed out in my last article the ground in the New Zealand nursery, fertile as it was, responded to a dressing of lime. It should be noted that Mr. Barbre uses 'soil' - any soil regardless of its fertility - and peat. To this he adds an artificial compound. What has he against using leaf mould, stable manure or compost? Or why not use a liquid fertilizer made from any of the above?
Whether the lime or the shade or the move improved Mr. Erdlich's R. 'Loderi King George' I would not say. The plant has improved, it is alive, and it is healthier than it was before. Apart from such habitually anemic plants such as R. 'Pink Pearl', R. 'Britannia', or R. 'Diane', the Loderi group as a rule show yellowing to the foliage to a greater extent than other rhododendrons. That lime can cure this rather than kill shows that lime is indeed a useful medium.
We had the same improvement with a small plant of R. 'Beauty of Littleworth' and a large plant of R. 'Jean Marie Montague'. When these were given to us the foliage was a bright healthy green. They were planted in a recently dug portion of the front lawn where the turf had been buried and the pure sand turned up to the surface. The foliage of both went yellow, not I would think from the absence of any single element but from general starvation. I limed the entire area, the color of the leaves returned to normal and the plants look healthy. Since then we have planted 80 rhododendrons and azaleas in this area and the only one that looks as though it is in distress is a small seedling of R. sinogrande .
This soil is low in fertility, not high in pH and when the former condition is corrected we shall have land that will grow anything. I feel that the dressing of lime released sufficient elements to enable the plants to obtain some of the necessary plant foods.
There is a section of garden writers who claim that lime will poison Ericaceous plants. Their experience I am sure is based on the fact that these plants will not grow in areas of England where free lime is available to plants. Because they do not understand why the plants die they use the word 'poison'. But none of these people have ever tried to lime a plant, at least I have never heard of anyone doing so, it is simply a case of following the leader. I have never killed a rhododendron by liming it and at the present time I don't think it is possible.