Can You Bottom Water Soil Blocks?

Soil blocks are a great option for helping seedlings grow. They are eco-friendly and take up less space than traditional pots. But can you water soil blocks like any other growing medium?

You can bottom water soil blocks. Bottom watering is the best option for soil blocks because it helps prevent soil erosion. To bottom water soil blocks, place them on a deep tray and add water slowly until the entire block is saturated.

This article will talk about how to bottom water soil blocks and the benefits of bottom watering. I will also discuss the benefits of using soil blocks and how to make them yourself!

How To Bottom Water Soil Blocks

Bottom watering soil blocks requires a little setup but is easy to maintain. Here’s how to do it:

  1. Place your soil blocks onto a tray. The tray will need to have sides that are at least 0.25 inches (0.63 cm) deep, preferably deeper, to prevent the water from flowing over the sides. An aluminum lasagna pan or edged baking sheet are good options.
  2. Leave room for watering. You should leave some space on the tray, so you don’t risk getting water directly on top of the blocks.  
  3. Pour water over the side of the tray. Use a cup or watering can to add water to the empty space of the tray, keeping it close to the tray to avoid splashing. Slowly add water until you reach 0.25 inches (0.63 cm) of water. 
  4. Ensure the entirety of the blocks is moist. If the blocks absorb all the water and still seem dry on top, add a bit more water, giving the blocks time to absorb the additional water before adding more. If you have different sizes of soil blocks, separating them by size in different trays will help you avoid overwatering some and underwatering others.

Check on your soil blocks daily to ensure they do not dry out. Watering frequency will depend on the soil type, ambient temperature, and humidity. After a week or two, you will learn how often your plants need watering.

Benefits of Bottom Watering Soil Blocks

Since soil blocks are not housed in pots, they need to be able to hold their structure. This requires the soil to be packed tightly. Although they hold their own shape, they are still quite fragile. When you water soil blocks from the top, the water can erode the soil block or break it down completely.

Bottom watering is a gentler way to water the soil blocks and helps to prevent erosion. It also helps prevent over-watering by allowing the soil blocks to take up only as much water as needed. 

Since plants absorb water and nutrients from their roots, it makes sense that absorbing water from the bottom up helps ensure the roots get enough water. When you water from above, you risk not giving the blocks enough water to reach the roots.

Benefits of Using Soil Blocks

If you are used to using traditional pots for your plants, soil blocks may seem strange. However, soil blocks are a good alternative. 

There are three major benefits of using soil blocks over traditional pots. Soil blocks are easy to nest, provide plant roots with more access to oxygen, and take up less space. 

Soil Blocks Make Transferring Easy

Repotting plants can be a long and messy process. Moving a plant into a bigger block is quick and simple with soil blocks. Soil blocks come in three different sizes, 0.75, 2, and 4 inches (2, 5, and 10 cm). These blocks all nest or fit into one another to make transplanting simple. This gives the roots more room to grow without damaging them while transplanting.

Here’s a quick rundown of the best times to use each block size:

  • The 0.75-inch (2 cm) block is only used for the initial seed sprouting period
  • Once the sprout breaks through the surface, you should move it to the 2-inch (5 cm) block, even if you cannot see any roots. 
  • When the roots begin to show outside the 2-inch (5 cm) block, simply place the entire block into the hole in the 4-inch (10 cm) block.

Soil Blocks Provide Roots With More Oxygen

In addition to the nesting feature of soil blocks, they also provide roots with access to more oxygen. Instead of only having an oxygen source at the top of the ground, the plants have a closer oxygen source available on all sides. 

Oxygen makes the roots of a plant stronger. These strong roots give the plant a sturdy support system and help it absorb all the necessary nutrients.

Soil Blocks Require Less Soil and Take Up Less Space

Another benefit of growing plants in soil blocks is no excess soil. Unlike pots with a lot of soil that the plants may not need, soil blocks provide only the necessary soil and allow you to add more when the roots outgrow their current block. This saves money and resources by eliminating unnecessary soil.

Plants in soil blocks require less space for storage. This allows you to fit more plants on your windowsill or in your greenhouse. You can also store blocks together on a tray for easy watering and transport. 

How Do You Make Homemade Soil Blocks? 

To make homemade soil blocks, all you need is some soil blockers and some soil! You need to get soil blockers, select your soil, water down the soil, add soil to the blockers, and make holes in larger blocks.

You can purchase ready-made soil blocks, but the most cost-effective way to use them is to make them yourself.

Get Soil Blockers

Soil blockers are the best way to make soil blocks because they allow you to pack the soil very tightly. This will provide structure for your seeds and make the blocks less vulnerable to erosion.        

I recommend the Ladbrooke Soil Block Maker System (available on, which is durable and contains both the 0.75-inch (2 cm) and 2-inch (5 cm) blockers to get you started. 

Select Your Soil

You can use any type of soil you like to make soil blocks. Any soil with a good texture for planting will also work well for soil blocks. This soil will be an equal mixture of sand, silt, and clay. Check out this article to learn more about soil texture: The Ideal Soil Texture for Planting Explained

Penn State has published its own recipe for soil blocks, which you can check out here. They recommend adding peat moss to your soil to improve its texture.

Water Down the Soil

You’ll need to water down your soil before packing it into the blockers. Here’s how:

  1. Add warm water to the soil until it reaches a damp consistency. The soil will not hold its shape if it is too wet or dry. 
  2. Add water slowly until you can squeeze a handful of soil, and it will retain its shape but not drip too much.

It’s best to wear gloves for this process. If you use a soil mix with vermicompost, manure, or any other material that tends to have a lot of pathogens and bacteria, you’ll need to protect your hands and wash them thoroughly afterward.

Add Soil to the Blockers

Follow the steps below to add your soil to the blockers:

  1. Add soil to your blockers a little at a time to ensure you fill the entire area, including the corners. 
  2. Pack the soil as tightly as possible. 
  3. Ensure the soil reaches all edges to reduce erosion during transport and watering.

Make Holes in Larger Blocks

It is important that you add holes in the larger blocks to nest the smaller blocks inside. These holes allow for easy transfer when the seed sprouts or the plant roots begin to outgrow their blocks. 

  • The 2-inch (5 cm) should have a nesting hole that fits the ¾ inch (2cm) blocks. 
  • If you are making 4-inch (10 cm) blocks, they should have a 2-inch (5cm) hole to nest the smaller blocks.

Most blocker kits will contain cubes to make these holes. If you do not have one, you can use a piece of wood cut down the size of the smaller block. 


Bottom watering is the best option for keeping soil blocks hydrated. It helps the plant roots get all the water they need while preventing erosion. It also makes it easy to tell when your plant needs more water.

Soil blocks are a good option if you want to be able to transfer the plants into bigger blocks easily, help your plants develop stronger roots, and take up less space.

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

Recent Posts