A self-watering capillary tray is a wicking tray that has its own water source. It can be used to water seedlings in pots. All you have to do is occasionally top up the main water reservoir, and that’s all!.
They’re great for watering seedlings, freshly rooted cuttings, and anything other plants that require constant moisture.
Starting seeds in DIY self-watering seed trays is a great way to get your plants off to a healthy start. These trays provide consistent moisture to seedlings without you having to water them manually every day. With just a few simple materials, you can create an easy self-watering system that will keep your seeds happy and healthy.
What is a Self-Watering Seed Tray?
A self-watering seed tray is a container that can hold multiple seedling pots or cells and provide water to them automatically through a wicking system This allows you to avoid daily watering and ensures seedlings always have access to moisture
Self-watering trays use capillary action to move water from a reservoir up to the soil. The key components are:
- A water reservoir – usually a tray or pot filled with water
- A wicking medium – an absorbent material like capillary matting that wicks up water
- Seedling pots/cells sitting on the wicking medium
As the seedling soil dries out, the wicking medium draws water from the reservoir to replenish moisture levels. This creates a self-contained hydroponic system for starting seeds.
Benefits of Self-Watering Seed Trays
Self-watering seed trays offer a few advantages over traditional seed starting methods:
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Consistent moisture – Seedlings get water as needed, avoiding dry outs or overwatering.
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Less maintenance – No need to water manually every day once set up. Just refill reservoir as needed.
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Promotes healthy roots – Seedlings get moisture from the bottom up, encouraging deep root growth.
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Portable – Move seedlings easily since the water reservoir travels with the tray.
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Space efficient – Fit more seedlings in a small area since no room needed for watering overhead.
How to Make a DIY Self-Watering Seed Tray
Making your own self-watering seed tray is an easy project with minimal materials required Here are the step-by-step instructions
Supplies Needed
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Shallow tray or container with drainage holes – This will hold the water reservoir. Plastic seedling trays work well.
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Wicking medium – Absorbent material like capillary matting, felt, cotton towels, etc Cut to fit tray.
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Plant pots or seedling cells – Must have holes for wicking action.
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Water reservoir – A jar, container, or terracotta pot filled with water.
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Sealant (optional) – To seal reservoir if needed. Silicone caulk works well.
Instructions
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Prepare the reservoir. Select a container that will hold adequate water, like a terracotta pot or jar. Seal any drainage holes with sealant so it can contain water.
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Cut wicking medium to size. It should fit neatly into the bottom of the tray. Tip: Use root control mesh to prevent roots from growing into the wicking medium.
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Place reservoir in tray. Position it in center or corner to ensure all seedling cells have access.
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Add seed pots/cells. Arrange on top of the wicking medium, spacing evenly to disperse moisture.
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Fill reservoir with water. Pour water into reservoir container until full.
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Let seedling soil wick water. Wait for moisture to distribute through wicking medium into soil. May take a few hours.
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Plant seeds and place tray. Sow seeds according to packet directions. Situate tray in a warm, protected area with light.
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Top off reservoir as needed. Check water levels every 2-3 days, refilling reservoir to keep soaked.
Maintenance Tips
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Re-wet seedling soil if it dries out completely to reestablish wicking.
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Add water if reservoir empties. Keep it consistently filled.
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Monitor for algae growth in reservoir and change water if needed.
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Consider using water soluble fertilizer in reservoir for added nutrients.
Ideas for DIY Self-Watering Seed Trays
Almost any shallow tray or tub can be transformed into a self-watering system. Here are some ideas:
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Use a plastic seedling tray,dish tub, or recycled container. Ensure adequate drainage.
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Try a hydration station water bottle as reservoir. The long, narrow shape fits trays well.
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Repurpose food trays or takeout containers as mini self-watering trays.
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Add a layer of gravel or stones under the wicking medium to increase humidity.
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Use cotton pillowcases, shredded cloth, or old towels as a cheap wicking material.
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Stack two trays, one for reservoir and one for seeds. Allows easy refilling.
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Grow microgreens in a self-watering setup. They don’t need drainage holes.
Getting the Most from Your Self-Watering Tray
Position your DIY self-watering seed tray in a warm area with light. South facing windowsills work well indoors. Outdoors, choose a sheltered location protected from harsh sun and wind.
Monitor water levels in the reservoir regularly. Top it off every 2-3 days or whenever it gets low to ensure continuous moisture to seedlings. Add water soluble fertilizer to the reservoir as needed for an easy nutrient boost.
DIY self-watering trays are an easy, efficient way to get seeds started right. They prevent many common seedling problems like damping off and inconsistent watering. With just a bit of effort, you can build a system that practically grows your seeds for you!
How Does a Capillary Watering Tray Work?
This capillary watering tray works by the principle of wicking. Because the terracotta pot is porous, water seeps through it. The water then moves through the capillary mat, which absorbs it. Plant pots sitting on the capillary mat will wick water up from it to the plant roots.
- The water slowly leaks out of the terracotta pot and onto the capillary matting.
- The synthetic material used for capillary matting soaks up water like a sponge.
- The clay in the plant’s pot soaks up water from the wet capillary matting.
Here’s a simple explanation how capillary action works in a capillary watering tray.
- One of the things about water is that it sticks to itself. This is called cohesion. We’ve all seen this happen: two drops of water touch and join together to form a single drop.
- A property of water that makes things wet is called adhesion. Water also sticks to other things.
Small drops of water can join together to form a larger drop. In the capillary watering tray, the water in the potting mix connects to the water in the capillary mat, which in turn connects to the water in the terracotta pot. The three objects then work like one big wick, drawing an even amount of water across themselves as long as there is water in the terracotta pot to draw from.
So, when the plant pulls water out of the potting mix or dries out from evaporation, water will wick back into it to replace it. This way, the plant gets the water it needs and stays happy, which is how we like them!
Step 1. Gather the materials
The capillary watering tray is built around a plastic tray with drainage holes.
Pictured below is a plastic seedling punnet tray that is used commercially in nurseries. Any plastic tray with drainage holes will work. Plastic seedling punnet tray.
Next, we’ll need a sheet of capillary matting. It’s a grey synthetic fabric about 5mm thick that doesn’t rot when exposed to constant moisture.
It can be purchased from stores that sell greenhouse or hydroponic supplies.
Note: Instead of the capillary mat, you might be able to use any absorbent material—even newspaper—which will break down over time but is easy to replace. I haven’t tried it yet, but if you want to, please do so and let me know what you think! Capillary matting is a synthetic material that doesn’t rot and soaks up water very well.
The final component required is a small terracotta pot. The one used here is a 5″ (13cm) wide pot. Some silicone sealant will also be required. A small terracotta pot—the size doesn’t matter much here—it just needs to be big enough to hold water!
Step 2. Seal the drain hole in the terracotta pot with silicone sealant.
Silicone sealant (or something else) is used to close the hole in the pot so it can hold water and not leak. Allow the sealant to harden. Terracotta pot with drainage hole sealed with silicone sealer.
Step 3. Cut capillary mat to size
That is, the capillary mat needs to be cut so that it fits nicely in the tray’s bottom. Capillary mat cut to size to fit in plastic seedling tray.
Step 4. Sit terracotta pot water reservoir in the centre of the capillary tray
When the silicone sealant has dried properly, the capillary watering tray can be set up. Place the terracotta pot in the centre of the tray. This position ensures an even level of moisture right through the tray.
Step 5. Relocate pot and tray to a protected location
It’s hard to move the pot and tray once they’re full of plants, so put them where they’ll stay.
It’s best to put the plants somewhere protected with some shade or dappled sunlight. Weak plants don’t like being in direct sunlight or strong winds, and the water will evaporate faster in those conditions. Pot place in centre of tray for even watering of pots.
Step 6. Place pots of plants in tray and fill terracotta pot with water
Spread out the plant pots around the terracotta pot water reservoir so that each one gets enough water.
Next, fill the terracotta pot with water. Fill the terracotta pot water reservoir with water. In this picture, Japanese maple (Acer palmatum) seedlings in tube pots are placed on the capillary watering tray.
Step 9. Water the plant pots to start them wicking
Water the plants in pots until extra water starts to drip from the bottom of the pots onto the capillary mat. This will start the wicking process into the potting mix. Watering pots sitting on the capillary watering tray.
Step 10. Top up water level in terracotta pot as needed
Maintain the water level in the terracotta pot to ensure that the plants don’t run out of water.
If the terracotta pot accidentally runs dry, fill it back up with water and then water each plant pot again to get the wicking to work again.
DIY Self-Watering Seed Tray | Using Bootstrap Farmer Microgreens Tray | water seedlings while away!
FAQ
Do self watering seed trays work?
How do you make a homemade self watering system?
What can I use instead of capillary matting?