Triangle Wicking System — Three £20 Planters, One Corner

Container

Triangle wicking system in a south-facing corner with three terracotta planters and a black centre pot, lettuce and other crops growing in all four positions — Three £20 wicking planters in a triangle, plus a fourth pot in the centre. Under £60 for the whole system.

I built a £20 wicking planter. Then I built two more and arranged them in a triangle to fill a dead south-facing corner where nothing else quite fitted.

This is not a new system. It is three of the same system arranged to make use of an awkward space, plus a discovery during the build that added a fourth growing position for free. If you have not read the single planter guide yet, start there. This page assumes you know how they work.

The real story here is the lettuce. I planted supermarket root stumps into these planters and had lush, productive lettuce growing back within five weeks. That is the centrepiece of this guide.

The Triangle Layout

Three Tesco wicking planters, each with its own trough reservoir, arranged in a triangle with all troughs facing inward. They are not linked together. Each planter is completely independent with its own water supply. The troughs face inward partly to keep things tidy, and partly because the plan is to link them to a shared central reservoir in the future. For now, three separate reservoirs work perfectly well.

The whole thing fills an awkward south-facing corner between the house wall and the side path. About 80cm across at the widest point. Previously dead space with some self-seeded chard and a bolted kale plant. Now it grows food.

The triangular corner bed before setup, showing self-seeded chard, a bolted kale plant, and bare soil in a south-facing corner against the house wall — The corner before: self-seeded chard, a bolted kale, and wasted south-facing space.

Site Preparation

I dug out the triangular bed, cleared the weeds, and laid gravel to create level bases for each planter. The ground here slopes slightly, so level gravel pads were essential to stop the troughs draining to one end. Brick edging around the perimeter defines the bed and holds the gravel in place.

The black centre pot sitting on a gravel base with a spade alongside, showing the level gravel pad prepared for the planter — Gravel base for the centre pot. Level ground matters when your reservoir is a shallow trough.

The Fourth Pot

This was not planned. Once the three planters were in position, there was an obvious space in the centre where they all meet. A plain black pot fitted neatly on top of the three troughs.

I trimmed the top of this pot down so it would not tower over the terracotta planters around it. Then I used the cut rim as a template, flipping it onto the ground and drawing circles to mark where to place the gravel bases. A genuine aha moment from actually building the thing rather than planning on paper.

The centre pot has a wick going into each of the three independent reservoirs below. So it draws water from all three, and if one trough runs dry the other two keep it going. It is a surprisingly resilient arrangement for something that emerged by accident.

The triangle wicking system just after planting, showing three terracotta pots with lettuce root stumps and one black centre pot, troughs visible between them — Day one: three wicking planters with lettuce root stumps, the black centre pot sitting on top of the three troughs.

The triangle system from a wider angle showing curved brick edging around the perimeter, all four pots in position against the house wall — Brick edging around the perimeter. The curve follows the natural shape of the corner.

What It Cost

Item	Cost
3 x wicking planters (pot, trough, board, wicks, gravel, coir)	~£60
Centre pot (already had one)	£0
Wicking rope for centre pot	~£1
Gravel for bases (leftover from other builds)	£0
Bricks for edging (reclaimed)	£0
Lidl living lettuce (2 packs)	~£2
Total	~£63

Under £60 if you are building the three planters from scratch. The gravel bases, bricks, and centre pot were all things I already had. The lettuce cost about £1 a pack from Lidl.

The Lidl Lettuce Hack

This is the real story. I first described this technique in the NFT herb wall guide where it worked brilliantly in an active pumped system. The question was whether it would work just as well in a completely passive wicking planter with no pump and no moving water. It does.

The Technique

Lidl (and some other supermarkets) sell living lettuce with the root systems still attached. They have been grown commercially in hydroponics. Each pack is actually two or three individual plants sharing a root ball.

Buy them. Eat the lettuce. Then split the root stumps apart and plant them in the wicking planters. That is it. The constant moisture from the wicking reservoir does the rest.

Two packs of Lidl living lettuce on a yellow floral surface, one green variety and one red and green mix, both with full root systems visible in coir plugs — Two packs of Lidl living lettuce, about £1 each. The roots are the valuable bit.

Three individual lettuce plants split apart from one pack, laid on a white plate showing their separate root systems — one green, one mixed, one red variety — One pack splits into three individual plants. Each has its own root system and will grow independently.

Close-up of three lettuce root stumps on a white plate showing the dense root networks and trimmed leaf bases, ready for planting — Close-up of the root stumps after the leaves have been eaten. Those roots are what drive the regrowth.

Planting the Root Stumps

I spaced six root stumps per pot, pressing them gently into the coir with the growing point just above the surface. The wicking reservoir was filled, and the coir was already moist from the wicks doing their job. No further watering needed on planting day.

Overhead view of a wicking planter with six lettuce root stumps freshly planted in coir, small leaf stubs visible on each — Six root stumps planted in one pot. The stubs look tiny now. Come back in five weeks.

Five Weeks Later

This is what those root stumps turned into. Five weeks of passive wicking with no intervention beyond topping up the trough every few days.

Wicking planter five weeks after planting, showing regrown red lettuce varieties, a transplanted perpetual spinach in the centre, and beetroot seedlings emerging from the coir — Five weeks later: regrown Lidl lettuce, a self-seeded perpetual spinach transplant holding court in the centre, and beetroot seedlings pushing through.

Second wicking planter showing regrown lettuce with one bright green head and two dark red lollo rosso varieties, all lush and healthy — The second pot. One bright green head and dark red lollo rosso varieties. All from stumps that cost pennies.

Overhead view of a wicking planter with regrown lettuce showing one vivid green plant and two deep purple-red varieties contrasting against the coir — Overhead: the colour contrast between varieties is striking. Green and red from the same pack.

The lettuce grew back healthier and more vigorous than I expected. The passive wicking system keeps the coir consistently moist without waterlogging, which lettuce loves. No pump, no timer, no daily watering. Just physics and a trough full of water.

This confirms what I suspected from the NFT herb wall: the technique works across completely different systems. The NFT wall is active, pumped, and soil-free. These wicking planters are passive, coir-based, and have no moving parts at all. Same result. The roots just grow.

What Else is Growing

The lettuce is the headline, but there is more going on across the system.

Carrots in the Original Planter

The original single wicking planter from the £20 build guide has rainbow carrot seedlings coming up. They are following the spiral sowing pattern from the original build and are establishing well. This planter sits at the front of the triangle arrangement, so all four positions are now producing.

Overhead view of the original wicking planter showing small carrot seedlings emerging from the coir in a spiral pattern — Carrot seedlings in the original £20 planter. The spiral sowing pattern from the first build is visible.

Beetroot

Beetroot seeds are in as succession planting. Once the lettuce is harvested and the weather warms up, the beetroot will take over those positions. Having multiple planters means you can stagger your plantings rather than having everything ready at once.

Self-seeded Chard

While prepping the corner bed, I found self-seeded chard and perpetual spinach growing in the soil. Rather than composting them, I transplanted a few into the wicking planters and into the old tomato gutter grow system. Free plants from a bed that was about to be cleared anyway.

The Experimental Platform

Four identical growing positions. Same pot design, same coir, same wicking mechanism, same sun exposure. Change one variable and you have a controlled experiment.

Same crop, different nutrient concentrations. Same variety, different EC levels. Same conditions, two different lettuce cultivars. The possibilities are obvious, and at under £20 per unit the cost of adding a control group is trivial. Detail comes in future experiment posts.

The completed triangle wicking system viewed from above, showing all four pots in position with brick edging, gravel bases visible, and the south-facing house wall behind — Four identical growing positions in one corner. The starting point for controlled experiments.

What I'd Do Differently

Level the gravel more carefully. One of the troughs drains slightly to one end because the gravel base was not perfectly flat. It still works, but the reservoir capacity is reduced. Five extra minutes with a spirit level would have fixed it.
Trim the centre pot before positioning. I trimmed it in place, which was fiddly. Easier to measure, cut, and then place it.
Plant more root stumps per pot. Six per pot worked, but there was room for eight. The lettuce fills out regardless, and more plants means a faster visual impact and more variety in the harvest.

What's Next

Harvest and rotate: The lettuce will be picked and replaced with beetroot as the season progresses. The wicking planters make rotation simple because each pot is independent.
Carrots in the original planter: The rainbow carrots are establishing well and will be the next big result. Root vegetables in a wicking planter are the real test of the system.
A/B experiments: With four identical positions, proper controlled experiments are planned for later in the season. Same crop, one variable changed.
Linked reservoir: Eventually, connecting the three troughs to a shared central reservoir with one fill point. For now, three separate fills every few days is manageable.

Wide view of the triangle wicking system in mid-April, showing all three terracotta pots with established lettuce growth, the black centre pot, and the original planter with carrot seedlings at the front — Mid-April: lettuce thriving in the back two pots, carrots establishing in the front. All passive, all self-watering.

Watch the harvest

The lettuce is about to be picked, the carrots are establishing, and the A/B experiments are being planned. The Glut is where I share results, harvest data, and what I cook with it all.

Free newsletter. No spam, ever.

Frequently Asked Questions

How do you regrow lettuce from supermarket scraps?

Buy living lettuce with roots still attached (Lidl sells these regularly). Eat the leaves, then plant the root stump in moist growing medium. In a wicking planter, the constant moisture supply means you barely need to think about watering. Expect harvestable leaves again within 4 to 5 weeks.

Can you arrange wicking planters to fit awkward spaces?

Yes. Because each planter is independent and self-contained, you can arrange them in any configuration that fits. Three in a triangle fills a corner. Two in a line fills a narrow strip. The troughs face inward to keep things tidy, and each unit waters itself from its own reservoir.

What is the cheapest hydroponic system to build?

A single Tesco wicking planter costs under £20. Three of them arranged as a triangle system costs under £60 and gives you four growing positions. No electricity, no pump, no specialist tools.

Can you grow vegetables in a small garden corner?

A south-facing corner is ideal. This triangle system fills a space roughly 80cm across with four independent planters, each producing salad leaves, root vegetables, or herbs. The wicking reservoirs mean each pot only needs topping up every few days.

Related growing guides

Build a £20 Wicking Planter from Tesco Gutter NFT Herb Wall

Triangle Wicking System — Three £20 Planters, One Awkward Corner