How to make a good drainage layer?

How to make a good drainage layer: Drainage is important, especially for potted plants. It may also be necessary in open ground if your soil is heavy and clayey. Excess water suffocates the permanently wet roots. 

Under these conditions, root rot is not uncommon. It gradually leads to the death of the plant. We explain to you how to make a good drainage layer quite easily. Follow the leader.

What is a drainage layer used for?

A drainage layer has several advantages. It promotes water evacuation and limits the risk of root rot. It also reduces the development of fungi and the appearance of cryptogamic diseases such as damping off or armillaria. 

These diseases weaken plants which wither and die. Furthermore, once established, the fungi spread their spores which remain in the ground and continue to affect the plants. 

A real vicious circle from which it is difficult to escape. Soil properties are also affected by this excess water. 

How to proceed?

Drainage layers are useful for potted plants, but also in the ground. However, the installation methods are different. [How to make a good drainage layer]

In a jar 

Flower pots and plants must be pierced to allow water to drain. Some are sold already with holes (this is particularly the case for terracotta pots), others have areas to be drilled. A large hole and several small ones will help the water to drain. They are essential.

Planters, bins, and pots with integrated storage, as well as those with a double bottom, do not need to be drilled. 

Here are the steps to create a drainage layer in a pot, tray, or planter: 

  • Pierce the pot if it isn’t already.
  • Place clay balls, terracotta pot shards, or gravel in the bottom of the pot. This layer must represent 20% of the tank. So, for a pot 20 cm high, the drainage layer should measure 4 cm high. 
  • Cover with potting soil suitable for your plants. Leave enough room to place the root ball.
  • Install the root ball and fill in any empty spaces. 
  • Tamp down.
  • Water.

In the open ground

Clay soils do not allow water to infiltrate deeply. It stagnates on the surface or makes the soil heavy. The roots then lack air. Furthermore, it is an environment favorable to the development of cryptogamic diseases. 

TIP: Do not drain light soil, such as already sandy soil, because it risks drying out even more quickly. [How to make a good drainage layer]

Here are some tips for draining garden soil: 

  • The easy tip: dig a hole twice as big as the root ball to be planted. Above all, add several centimeters of depth (20 to 40 cm, depending on the size of the root ball) to place gravel, shards of terracotta pots, or clay balls in the bottom of the hole. 
  • A complementary action: a layer of gravel on top of the soil, like mulch, also improves drainage.
  • Lighten the soil: if your potting soil is heavy, mix in potting soil or compost to lighten it. Adding sand is only recommended for plants that enjoy this particular soil type, such as cacti and succulents.
  • In the vegetable garden: you can dig narrow and deep furrows around the planting area. Then fill them with river sand. Water will seep in, which will dry out the rest of the garden. The heavier and wetter the soil, the higher the number of furrows will need to be. Installing your vegetable plants on mounds made of potting soil and compost is also a solution that will improve the properties of the soil over the years. 
  • A ditch at the bottom of the land: digging a ditch in the lower part of the garden is a way to encourage water runoff.
  • The lost well: it allows water to flow into it and infiltrate deeply. A well 1.50 m deep and wide must be covered with geotextile at the bottom and on the edges. Stones (or tiles) are placed at the bottom, then gravel and finally sand. 
  • Installing a drain: this is a solution that requires more substantial work. It is rather reserved for very clayey soils. A network of trenches (deep enough to be able to plant plants on top) must be dug with a spade into the ground. We then install felt and specific sheaths in this network. Finally, you will need to fill the trenches with garden soil. 

Drainage is therefore a significant step when you want to grow plants. By taking care to properly create this drainage layer, you will optimize the development of your plants.

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