When we embark on a landscaping project, it is essential that we know at least two things: what are the current problems in our garden that we want to improve, and what types of plants we’d like to raise. This is important because the distribution of the ground and the selection of the most appropriate soil for our cultures – whether we expect to eat from our garden or we simply wish to create a handsome and harmonious ensemble – will define the successful outcome of our plans, as plants are living organisms with specific needs.
Trees, shrubs or flowers, that we would never imagine growing and blooming in proximity in nature, may coexist in full glory in a residential garden. A sandy coastal backyard can be transformed into an all-green, highly productive vegetable garden, if we fill in large flower beds with rich loam soil. That piece of land by the fence wall, which used to gather stagnant waters, can host a number of graceful plants and flowers – all that needs be done is to perform a few simple tasks: excavate, lay gravel and/or other permeable materials for the effective drainage of the lot, fill in with soil, voilà!
After installing a good drainage system and after laying the substrate of our garden with materials that will help improve its functionality (e.g. gravel, geotextile, etc), it is time to lay the garden soil level and proceed to planting.
By ‘garden soil’ we mean the topsoil, down to 24 inches deep, where plants sprout and grow. It is composed mainly of humus and mineral particles: clay (very fine grain), silt (medium-sized grain) and sand (large grain). The content percentage of the above mineral materials varies among different soil types.
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When adding topsoil, don’t just throw it on top of the ground.
Always incorporate some or all of it with the native soil,
or at least create a shallow transition zone between the two.
This way, water will be able to move freely across the newly created ground,
preventing the creation of soggy areas in the garden.
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How to tell apart the various soil types:
The simplest method is to pick up some soil when it’s moist and compress it.
- Sandy soils will feel gritty
- Loam soils will break apart into loose chunks
- Clayey soils will cling together in a ball
Here are some quick, empirical and effective ways to diagnose your soil before proceeding to your landscaping and gardening plans: Soil Types and Testing
In the section below we will examine the most common soil types, their characteristics, how they respond to cultivation, and what we can do to improve them for greener and healthier gardens.
1. Sandy soil
It is light and fluffy, therefore very easy to cultivate, as it allows the soil to break up and be worked for planting. It also helps prevent crusting, which could block seeds from breaking the surface.
As sand is a quite loose material, it allows water, the sun and its beneficial spring warmth, as well as the air and oxygen to permeate more easily and in greater depth than other types of soil.
Yarrow (Achillea millefolium) is a very useful
plant for preventing soil erosion due to its
resistance to drought. It also repels bad insects and
attracts good ones, while directly improving the
health of sick plants when grown near them.
Yarrow grows exceptionally well in well-drained
soils: sandy soils are ideal for the growth of this
Downsides: Sandy soils
- are not appropriate for plants with small root system, because their consistency does not allow for good support and the plants remain vulnerable to the force of the winds; furthermore, such plants will suffer during the hot season, when their tiny roots will be struggling to absorb scarce drops of water from a quickly drained ground;
- as water and humidity are quickly drained, they carry along all the useful nutrients that get washed away, far from the topsoil where they are most needed.
We can improve our sandy soil significantly by mixing it with clay, manure or humus.
2. Clayey soil
It is very consistent, which makes it exceptionally hard to permeate by water, light and air. It keeps warm during winter, and retains water in the summer, but may crack deeply in high temperatures; when dry, you can feel how heavy and hard this material can be.
Due to its dense, compact nature, the roots of plants penetrate it with great difficulty and may suffocate from inadequate airing. During droughts, when superficial humidity evaporates, the plants cease to grow, sometimes even shrivel.
We can improve clay by mixing in sandy soil, manure or humus.
3. Chalky soil
It comes from calcareous (lime-rich) soils and therefore very alkaline.
Most chalky soils are shallow, free-draining and poor in nutrients; however, when clay is present, nutrient levels may be higher and water holding capacity better. On the other hand, the high alkalinity of the ground will still prevent the absorption of iron by the plants.
Mix in sand and/or manure. Avoid limestone and dolomite, as they will increase the soil’s alkaline content.
4. Loam soil
Dark brown or black, it contains almost equal amounts of sand, silt and clay (40-40-20 %). It is outstanding for cultivation, as it is rich in nutrients and humus, retains the necessary amounts of water while at the same time allowing excess water to drain away, and it is easier to till than clayey soils.
Loam soil keeps relatively warm during the harsh winter days, while it doesn’t bake in the fiery summer. It also promotes the growth of beneficial microorganisms which help keep the soil healthy.
Loam soil is the gardener’s friend: a rich, healthy topsoil which, of course, still needs good management, so as not to get depleted and impoverished. Working in organic materials from time to time will keep the soil in good condition. We can also use it to enrich poor soils (clayey, sandy and chalky).
5. Silt soil
It is similar to loam soil, but contains smaller ratios of both sand and clay particles. Silt is the material deposited in river banks and floodplains and, therefore, it is very fertile ground. It holds water, like clayey soils do, yet it drains much better.
Silt soils tend to erode easily, as their fine, light particles are blown away by wind and carried down by water streams. They also tend to get compacted easily — avoid walking on flower beds and prefer to use pathways, such as narrow boards, between beds and plots, or build raised beds.
Mix in mulches, sand and/or other drainage assistance materials.