In landscaping, thinking about the design in three dimensions can always help you to come up with options that work with nature and with the terrain. Having some areas of the garden lower than others is one option that can help achieve the results you are looking for.
A “sunken garden” may mean different things to different people. So, to make sure that you meet your goals for a sunken garden, it is important to determine exactly what you mean by this concept, and what precisely you hope to achieve.
What Is a Sunken Garden?
This term refers to an area of your garden that is lower than the surrounding ground level. This might be a lowered area for planting or an area for outside recreation that sits below neighboring plantings.
Sunken gardens come in a wide range of shapes and sizes. They vary from small beds in a tiny outside space, slightly lower than the surrounding soil, to grand lowered garden areas surrounded by impressive retaining walls.
Sunken Planting Areas
First of all, let’s take a look at sunken planting areas and why you might want to create planting areas which are slightly lower than the surrounding soil.
This type of sunken garden is all about water. By creating dips or hollows in a garden landscape, you can create areas where water gathers. These planting areas generate different growing conditions, which allow you to grow certain plants more effectively within your garden or manage water more wisely.
Bog Gardens and Natural Ponds
One example of a sunken garden of this type is a natural or manmade hollow in a landscape that is used to create a damp or watery environment suited to marginal or aquatic plants.
By placing a pond or filling a hollow with moisture retentive organic materials, you can create a sunken garden that is a watery zone—with far more water than the surrounding terrain.
When placed in the right location, such a feature makes a wonderful habitat for wildlife and potentially helps to drain excess water from other waterlogged areas.
Where rainfall is low, planting basins can be used to slow the flow of water and retain it within a garden. Features like rain gardens are a type of planting basin, where water is retained within the landscape.
With careful thought as to positioning, these slightly sunken areas within a garden reduce the need for irrigation and, when planted correctly, allow gardeners to use water wisely and minimize water use.
Sunken Waffle Gardens
A more evolved version of this simple idea is the concept of the waffle garden. This is an idea that was used by native Americans growing in arid areas.
They created a series of small sunken planting areas filled with organic matter within a series of raised berms which, when viewed from above, looks rather like a waffle.
These areas allowed for better water retention in dry areas and are a great solution for low water and desert areas.
Sunken Patio Gardens or Seating Areas
The second type of sunken garden is primarily about creating areas for humans to use within a garden, rather than providing optimal growing conditions for plants.
Sunken patio gardens or seating areas are lowered areas within a space which are used to create a wonderful sense of privacy and seclusion, as well as sheltered conditions.
These areas can create warm and sunny spaces out of the wind, and a comfortable microclimate for people and plants. They are usually more deeply incised into the ground, with a central area surrounded by earth held back by retaining walls.
The key thing to remember when creating a sunken garden of this type is that water flows downward. Drainage is something that you most definitely need to consider—or your sunken garden could potentially turn into a swimming pool.
French drains or other land drainage techniques can be used to ensure that water won’t pool in the base of a sunken garden. Using permeable materials will allow excess water to drain away freely.
Once the basics of the drainage and retaining walls have been created, you can think about what features you might like to add to your sunken garden area.
Water features, fire pits, outdoor cooking, dining or seating areas are all popular options. At the tops of the retaining structures, at ground level, planting can be at head height when people are seated within the sunken garden. So, using fragrant plants can be a wonderful idea. With plants at head height, you can really get up close and personal with the planting.
You can also incorporate plenty of plants in the base of the sunken garden area, either in the ground around the edges of the recreational space or in pots. Remember, the sheltered conditions allow you to grow plants that might not thrive in other parts of your garden.
There is a lot to think about when digging down in any garden. But these are just some sunken garden ideas that you might consider including within your garden designs.