Making a Wicking Pot Growing System

I’ve been using wicking pots since 2017 and I’m convinced they’re the best method for pot growing tomatoes, peppers, aubergines and cucumbers. I started with Quadgrows and Chilligrows but over the last few years have experimented with making my own wicking pots. My latest design seems to have cracked it! It is arguably superior in that it has a larger reservoir and saves a third on the cost of a Quadgrow.

What are Wicking Pots?

Wicking pots are a self-watering pot system that ensures the growing medium is at near optimum, containing both moisture and air. Both are necessary for plant growth. A cross between an aerated hydroponic system and standard pot growing. In some ways similar to ring-culture, which was popular with keen tomato growers in the past.

They are in three parts:

1. The reservoir that stores and supplies water and nutrients.
2. A wick (usually made from horticultural capillary matting) that transfers the water and nutrients to the growing medium
3. A pot that contains the growing medium and, of course, the plant itself.

Advantages of Wicking Pots over Standard Pot Growing

Standard pots are usually watered daily or, at best, twice daily. Initially, the pot is saturated, which displaces any air from spaces in the growing medium. Strangely, plant roots do require some oxygen and it is easily possible to drown plants.

Hydroponic systems, where the roots are continually immersed, provide the necessary oxygen by aerating the water. Similar in some ways to the air stone bubblers used in fish tanks. These require continuous power to the pump to function. Power is obviously not available in all greenhouses.

As the day proceeds, the water is absorbed by the plant, which sucks in the air required by the plant to live. Once the remaining water has been used, the compost dries out. If the pot gets too dry, the plant become thirsty and can begin to wilt. Tomatoes in particular can be badly affected by irregular water availability, with fruits developing blossom end rot.

With a wicking pot system, refilling the reservoir is usually a weekly task, although the reservoir may hold enough water to last a fortnight or more. However, forgetting to refill the reservoir when needed is likely to be as problematic as forgetting the daily watering of pots.

Early Attempts

Initially I thought to just sit a large pot in a seed tray of water. This didn’t work as the compost in the pot absorbed water at the base but failed to take it up to the top. Using some capillary matting as a wick solved that problem, giving even moisture availability throughout the pot.

After a while the seed-tray nutrient solution grew algae becoming a slimy, smelly mess, basically. Obviously, something more sophisticated was required. Something that would act as a reservoir but not allow light into the water.

Some searching about on eBay resulted in my buying a black plastic box to act as a reservoir. This worked in that it prevented light causing problems with the water, but the lid was a little too flimsy to support the pot well. It was also too small to comfortably fit 2 large pots. However, it proved that it was possible to build my own working, inexpensive wicking pot system.

I’ve now developed a system – detailed below – that ticks all the boxes. The lid is strong enough to hold the pots and works just as well as my Quadgrows but cost less. It’s not quite as neat as the original Quadgrow but since that changed to the current version with 2 double potholders linked by a tube, just as convenient. The reservoir holds significantly more, reducing how often it needs refilling.

How to Build a Wicking Pot System Similar to a Quadgrow For Less

Parts Required for a 4 Pot System:

• Reservoir – 2 off Wham 36L Heavy Duty Storage Box & Lid (Halfords) £20.00
• Pots – 4 off 11L Square Plastic Plant Pots (Elixir) £10.99
• Wicks – Capillary Matting (Elixir) £7.99

Total Cost £38.98

Note: I buy my matting in 1m X 10m packs because I use it to make new wicks for the Quadgrows and on benching to keep plants watered. Any pot of suitable size will do, just go for a strong pot that will last for years. If growing peppers, you can adapt the design for 3 5.5L pots

Tools Required

• Electric Drill
• Hole saws approx. 25mm and 50mm diameter
• Scissors

Time Required

Less than 15 minutes (Excluding the time it took me to find my hole saw set and recharge the drill’s battery!)

Method to Make the System

Use the 25mm hole saw to make a hole in the centre of the bottom of the pots.

Place 2 pots on the lid of the Wham storage box, in the corners and use the hole in the pots to mark out where the holes need to be in the lid. Drill these out with 25mm saw,

Between the 2 pots at the front of the lid, drill out a hole using the 50mm saw. This will be used for adding water to the reservoir.

Cut strips from the capillary matting approximately 100mm (4 ins.)wide. The strips need to reach the base of the reservoir, go up through the pot, bend and go to the side of the pot and then up to the top. Allowing a little slack, 60cm (24 ins.) length was sufficient.

Feed the capillary matting wicks through the bottom of the pot and down through the lid of the reservoir. Job’s a good ‘un!

Growing Medium

You can use a multipurpose compost to fill the pots. If available, adding 10% perlite or vermiculite to lighten the compost is beneficial, but not necessary with a good commercial compost.

Feeding Wicking Pot Systems

The compost will usually have enough nutrients to last the plants for 4 to 6 weeks. Many brands will give an indication on the bag of how long the nutrients in twill last. After that period, start adding suitable soluble feed to the water at half strength, moving up to full strength when fruits begin to form.

Plants grow so well in wicking pots that they use up nutrients faster than they would otherwise. Because of this, it is important to use a suitable fertiliser containing a full range of micro-nutrients and elements, such as those used in hydroponic systems.

2 Part Systems

Most of the suitable fertilisers come in two parts. The reason for this is that complete fertilisers need to contain calcium. Calcium is a vital secondary nutrient, essential for plant growth and development. It improves the absorption of other nutrients by the roots and the delivery of nutrients from the roots to the rest of the plant. Without sufficient calcium growth is, at best stunted. Tomatoes will suffer blossom end rot without enough calcium.

When soluble calcium salts are mixed in solution with soluble phosphorus salts they react together and produce an insoluble calcium salt. This insoluble calcium salt is not available to the plant.

The longer the calcium and phosphorus are mixed, the more of the soluble calcium is converted to the insoluble form. This limits the value of the fertiliser as the bioavailable soluble calcium level decreases over time.

Because of the calcium decrease, I now use S-Chelate Protom fertiliser. It has a slightly higher calcium level than S-Chelate 12 Star fertiliser which is very useful in our soft-water area. Soft-water doesn’t contain as much calcium as hard-water. S-Chelate solves this problem by solubilising the calcium with a proprietary chelation technology.

Also, S-Chelate comes as a very concentrated powder which is mixed at point of use, rather than pre-mixing two concentrated solutions that are then combined at point of use. Much more convenient and environmentally better, reducing shipping costs.

Organic Feeding with Wicking Pot Systems

I have not tried growing organically with wicking pot systems, but some readers report being able to successfully.

Generally the growing medium they use contains a high proportion of rich home-made compost with added perlite or vermiculite to improve moisture transmission. The nutrient mix supplied with the water utilises comfrey liquid and or liquid seaweed-based, organic fertiliser.