Lime may supply the key to success for some of the plants in your garden.
My first experience with the magic which can be performed by the addition of lime to the soil came when I transformed a bed of sweet sultans from sickly plants to vigorous specimens with blossoms of exhibition quality.
In common with most beginners, I wanted to have outstanding success with one certain flower.
In my case, it was the sweet sultan Centaurea moschata (C. suaveolens), but if they flowered at all for me, the blossoms were small and the stems weak and crooked.
Secret Of Success
The secret of success was so simple that I blushed to mention my repeated failures.
I learned that the centaureas as a family is lime-lovers, and when I worked finely broken plaster rubble into the bed of sweet sultans the crop of cut flowers rivaled the florist’s finest, tallest plants were 51” inches in height and bushy, the long-stemmed blossoms huge and the colors particular bright.
My next revelation of the mag properties of lime concerned the admittedly difficult Thalictrum dipterocarpum.
Louise Beebe Wilder, accepted audit for generations of gardeners, furnish the clue to its successful culture, deduction as to its inability to thrive acid, or even neutral soil saved the plant of my flat of ailing young seedling that solitary survivor made the astonishing about-face.
I have yet to plant and live to grace my game for ten years in its well-limed spot.
Such spectacular results with so little effort aroused my interest to the point of obsession. Although experiments to ascertain the degree of soil acidity certain plants require have been given wide publicity, information about the effects of lime in the soil has not been well disseminated.
My accumulation of notes on the subject certainly provides facts enough to justify using lime as a sound working practice rather than mere theory.
Well-Limed Soils
Farmers and market gardeners find it profitable practice, for they know that many field and vegetable crops produce a consistently higher yield on well-limed soils.
Conversely, liming becomes necessary for most vegetables where the soil is inclined to be acidic.
Legumes usually require an alkaline soil, and soybeans, squash, asparagus, cantaloupe, cauliflower, onions, parsnips, and rhubarb appreciate extra lime in the soil.
Generations of adaptation to various environments have conditioned most of our favorite ornamentals to neutral soil, although carnations, gypsophila, delphiniums, mignonette, nasturtiums, sweet peas, and many others prefer sweet soil.
Lime Loving Plants
When plants are brought from high mountain ranges, deserts, plains, jungles, or any specialized environment, they cannot conform to the soil difference developed through centuries by our garden hybrids.
The difficulty and expense involved in obtaining these plants make it imperative to ascertain their special requirements and duplicate these as closely as possible in the garden.
In recent years, this process is usually undertaken with the greatest consideration regarding the acid soil group but with less understanding of where lime-loving plants are concerned.
It would be just as reasonable to hope those plants requiring an extremely low pH will thrive in neutral soil as it is to expect that plants native to a strongly alkaline territory will be satisfied with neutrality.
Natural Habitat
The best way to determine soil preference in plants is by reference to their native habitat.
Plants from the high Sierras, Rocky Mountains, or any other granite range will not tolerate lime in any form. But many other plants from the western plains are lime-tolerant, if not calciphilous.
A lime deficiency is now considered the main cause of their frequent-poop growth- in many eastern gardens. Therefore, many plants from the limestone ranger would require a straight acid soil treatment.
But further investigation will often prove that while the plant seemingly grows in leaf mold or detritus, the long taproot strikes deep into the crevices of the limestone formation below the humus of the surface soil.
Soil Acidity
The fact that many flower families are divided among themselves makes it even more important to consider the native haunts of the species in question.
Plant explorers and many of our nurserymen designate the locale, and often the formation found beneath the plants under discussion. This is often the key to their culture.
Soil above marble, limestone, and serpentine is almost certain to be alkaline, while that above quartz, granite, and mica are usually acidic.
Acidity generally prevails above sandstone and shale, although it may be neutral or even mildly alkaline.
Calciphobes
Where acid soils occur in nature, we find a class of plants to which the least taint of alkalinity is a deadly poison known as calciphobes. Conversely, where the soil is alkaline, lime lovers, or calciphiles, are found.
These plants seemingly depend on the action of lime to release nutrients in the forms most easily assimilable by their roots. This is done by altering the mineral compounds present in the soil to the essential elements required for plant growth.
It must be remembered that lime is not a fertilizer and is to be used only as an amendment to improve the texture and change the chemical analysis of the soil.
Its action is purely chemical, which process also greatly increases the activity of the beneficial soil bacteria.
Top Dressing of Limestone Chips
When it has been determined that the plant in question requires increased alkalinity, the next step is to decide in which form it is best to provide it. Many rock plants are happiest with a top dressing of limestone chips.
These also serve to protect the crown of the plant from undue dampness and the blossoms from being splattered with mud.
Old mortar rubble may be used as a top dressing or dug into the soil. The degree of pulverization depends on the plant and the location.
Coarse pieces used in the root run will help improve drainage and most nearly simulate the stone, calcareous range where limestone is unavailable.
Hydrated or Agricultural Lime
In garden beds and for field crops, it is better to use hydrated or agricultural lime, the proportions depending on the soil’s acidity and the nature of the proposed planting, or ground limestone, which can safely be used in large quantities where available.
Wood ashes and fertilizers with an alkaline reaction, such as bone meal and superphosphate without their usual gypsum content, may be used to advantage.
Frequency Of Application
Lime should not be needed more often than every two years. The alkaline reaction may continue for as long as five years or indefinitely, depending on the type of soil.
Because of the constant leaching, sandy soil, derived from granite and naturally inclining toward acidity, requires lime and fertilizers more frequently than close, fine-textured soil derived from limestone.
Glacial soils, silts, and loess deposited by wind will need constant attention. In contrast, a sedimentary soil of alkaline reaction may never need amendment except for the accommodation of acid-loving plants.
Provide Acid Soil Stations
It has become common practice in landscape design to provide for acid soil stations. Some provision for the segregation of calciphilous plants is also desirable.
Where such a grouping of plants is impossible, as in established plantings, the soil preferences of surrounding plants must be determined before lime or fertilizers of alkaline reaction are added to the soil.
The importance of this step cannot be overemphasized, as lime is an immediate and deadly poison to acid lovers and will do irreparable damage if allowed to seep into their root zone.
Establishing Alkaline Soil Stations
The idea of establishing alkaline soil stations may seem far-fetched. Still, it will surely appeal to the serious gardener as an easy way to get the best performance from this class of plants without damage to others.
In the rock garden and perennial borders, the sunny, open spaces might be designated as alkaline stations, as the lime lovers, broadly speaking, are sun-lovers, and the acid soil plants require shade.
There are exceptions to this rule in both groups which should be confirmed concerning local conditions such as altitude, humidity, summer temperatures, etc.
Soil Type
In certain regions, the soil type is so well known to eliminate the need for testing, except for the culture of those plants requiring a precise pH.
In other localities, acid and alkaline soils are found in a small area, often within the same garden. For example, the sandy soil of my old home, where I gardened for 15 years, was inclined to be acidic.
The water was soft, the table was low, and the soil was loose and perfectly drained. The new garden, not three miles away, has sweet soil with hard water at a high level, and the drainage is poor. The acid soil stations require constant observation and renewal.
Yet I have found that those plants with a decided sweet tooth need top dressings of plaster rubble for best results, just as they did in my other garden. Plants that are merely lime-tolerant thrive as weeds—a case in point being the henryi lily.
This small garden was practically overrun with them. Other lilies which are either lime-tolerant or calciphilous are:
- Lilium giganteum
- Martagon
- Aurantiacum
- Candidum
- Monadelphum
- Pomponium
- Testaceum
- The incorrigible scarlet Turk’s cap, L. chalcedonicum.
Preferred Lime
Violets also flourish here. I suffered a heavy loss on moving into the new garden when all my violet hybrids were thoughtlessly placed in an acid-soil bed. It did not take them long to die.
Their preference for sweet soil is undoubtedly the reason why violet growers give as a cultural tip the rather ambiguous advice that violets should not be planted under pine or redwood trees.
These directions apply only to varieties of the sweet violet, Viola odorata, as most species require acid soil. However, limestone chips are recommended in any compost prepared for V. alpina and V. pedatifida.
We find few families in which the members are unanimous in their needs. On the contrary, in almost every large genus, there are species as equally insistent in their lime hatred as the related calciphilous species are in their demand for it.
All achilleas and aethionemas are believed to need lime, and the dianthus family is in almost complete accord.
Schizanthus, when grown in pots, should have a handful of finely pulverized mortar rubble in each pot. Gloxinias will also make a finer growth in sweetened soil.
The lovely prairie gentian (eustoma) needs lime in the seed compost as well as a strongly alkaline growing medium.
An Alkaline Diet
All the border campanulas and many of the rockery species thrive in limey soil. Clematis as a family demands well-limed soil, exceptions being C. verticillaris and C. crispa, which require a pH of 5 to 6.
Scabiosa Caucasica
Scabiosa caucasica and its numerous beautiful varieties cannot be expected to thrive in acid soil.
Recalcitrant stock plants can often be coaxed to bloom by an application of lime as a top dressing, and the thrifty growth of wallflowers in alkaline soil is evidence that lime in some form is a requisite.
Sweet Soil
Generations ago, gardeners realized that bearded iris made their best growth in sweet soil, with consequent heavy liming the accepted procedure in preparation of iris beds.
This practice quickly fell into disfavor when it was discovered that the lush growth induced by applying lime rendered the iris more vulnerable to attack by fungus diseases.
This does not mean, however, that acid soil is preferable or that alkaline soil is not the finest medium for their cultivation, but only that lime should not be used to force a soft, spongy growth that may have less immunity to disease.
Alkaline Soil
A few of the trees which thrive in alkaline soil are the casuarina, catalpa, yellow locust, hickory, and walnut.
Among the evergreens are red cedar, juniper, and yew, the chalk soils of England boasting noble specimens of its finest development.
Just as the best results are obtained from acid-loving plants when special consideration is given to the soil, lime lovers, too, should be given the conditions they like. An application of lime to calciphilous plants will do wonders if they are growing on acid soil.
44659 by Lila Mccombs