Sunken tugboat planting beds

“Sunken O’ Tugboat” by no_akira


I’m just a muddy old Sunken Tugboat 

cargo: a spades-depth mound of tilth and worms

a waterline over two fathoms

and a beam of six paces

unfurling slowly my Chlorophyll sails

tacking to port, headway into a photonic storm


a thermal bow wave of warmed stones

afront of my cycloidal  fender of rubber

Crown passengers parade across the forecastle

Paired births clumped across the keel line


In the mornings I see my  sister ship Dawn then later Dusk

My aunts are behind and my nieces ahead

a fleet of Nine

Sometimes the aunts raise sails across the stern


This is always my annual journey

Chasing the orange orb and its looping, UV arc

long shadow of the wisening garden sailor


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This Sunken tugboat planting bed system is an alternative solution to the age-old Horizontal vs Vertical bed orientation puzzle. The answer is through a simple but obvious bit of design. Why be either-or when you can be both!

It is a uniquely shaped ‘informal potager’ meets ‘kitchen garden’ meets rectangular ‘yam mounds’ hybrid idea. Basically its a vertically positioned rectangular planting bed with a Full-sun facing rounded top end. A sort of shallow curve (cycloid) similar to an Egyptian Stelae shape. Because this shape only has one line of symmetry its much easier to position this planting bed pointing at the sun at 13:00pm (BST). Basically along a “North-to-South” axis or as close to this axis as your plot will allow.

The rounded Full-sun end is dedicated to a trio of your sun loving heavy cropping veggies planted-out horizontally curving across the semi circle (courgette, aubergines, bush tomatoes and chillies). Behind this crown we can grow our usual more shade-tolerant typically British crops in a paired bed. The dimensions of this planting bed create x3 crown and x6 paired vertical growing positions (15 growing positions in total) for your typically larger vegetables. An average sized maturing Potato plant being our standard size guide (14-16 inch circle).

Two more Sunken tugboat planting beds are dug next to the first one creating 3 planting beds. This creates your first “3Block” of side-by-side planting beds.

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At the very heart of this system is the Main, Second early and First early category of potatoes for which we require 3 planting beds. Each potato type planted in pairs along the vertical axes of these beds, 6 paired plants = 12 plants per type. Potatoes are the basic mainstay crop of the allotmenteer because they’re among the first crops to go into the soil and the last to come out across the six months of the growing season. They are fantastic because they are virtually maintenance free, plant-and-go. Every year we will rotate this 3Block of potato types from one 3Block to the next.

The other clever part is that we have created a horizontal Cycloid curve looping across the head of our 3block of planting beds, 9 sunny positions for those VIP full-sun warm-soil loving plants. That is potentially 27 heavy cropping plants from our 9 bed Sunken tugboat planting bed system.

The aim of this design is that by using standardised dimensions you save new starters a lot of  time and effort digging beds in wrong positions or digging the whole plot over or wasting money on wood enclosed Raised beds. Also the more widely Sunken tugboat planting beds are adopted across allotments the easier it will be for new starters to revive their new-to-them neglected plots.

Positives (Pros)

<< CLICK + line to expand or hide >>[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Unique shape with easy-to-grasp planting bed idea” collapse_text=”+Unique shape with easy-to-grasp planting bed idea” inline_css=”font-size: 11pt;” ]A unique design with its combination of horizontal Crown header ahead of vertically laid out paired-bed, breaks from convention. With its memorable boat analogy.[/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Thermal mass Heat-store using bricks, semi circle” collapse_text=”+ Thermal mass Heat-store using bricks, semi circle” inline_css=”font-size: 11pt;” ]I have used Block paving bricks as they are readily available; dense, frost resistant and a uniform size. They easily absorb solar thermal heat and continue to warm the soil an extra hour after dark. It also useful that nine blocks fit across a 16″ tyre, about 62 inches in width. Stones or rocks could also be used. Also looks attractive, form and function combined. Also Song Thrushes use these bricks as anvils helping to clear snails from your plot.[/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Quick-warming tyre, soil warmer idea” collapse_text=”+ Quick-warming tyre, soil warmer idea” inline_css=”font-size: 11pt;” ]A de-walled and cut through to break-the-circle tyre is stretched out and half buried at the top of our vertical planting bed. The cycloid shape of this adapted tyre also makes it easier to create the rounded end of our planting bed. The black rubber heats quickly in the sun warming the soil around our full-sun loving crown plants. Also it creates an impermeable barrier reducing water loss through the full sun facing soil.  The tyre is only sunken 2 or 3 inches into the soil and helps as a height guide for the soil level of our semi-raised bed.[/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Worm corraling due to the semi-circle rubber barrier” collapse_text=”+ Worm corraling due to the semi-circle rubber barrier” inline_css=”font-size: 11pt;” ]You will notice over the winter a greater mass of worm casts in the soil of the crown header section. It appears the worms are getting trapped in this cul-de-sac of rubber. Might be an idea to cover the area with fresh manure to provide food for our overwintering worms.[/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Crown header section for Snowflake plants and overwintering” collapse_text=”+ Crown header section for Snowflake plants and overwintering” inline_css=”font-size: 11pt;” ]Snowflake plants are those exotic vegetable plants that we all want to grow such as Aubergines; Chillies and Courgettes but which go on strike (stall) in the early outdoor British summer weather. Also its an ideal area to grow those few overwintering plants (onions, garlic) as they will be occupying that space until late May so when they come out you can transplant in the last of your sown-indoors plants. [/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Dedicated sections of the bed by plant requirements” collapse_text=”+ Dedicated sections of the bed by plant requirements” inline_css=”font-size: 11pt;” ]The dividing up of the planting bed makes it more obvious for the new starter were full-sun and shade tolerant plant types should go.[/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Semi-Raised bed digging concept ” collapse_text=”+ Semi-Raised bed digging concept ” inline_css=”font-size: 11pt;” ]The first time we dig the bed over it was to a spades depth but after adding the half buried car tyre, the height of the bed has then been increased by 3 inches. We then mound our soil up against the level of the tyre which means the depth of our soil is a third higher. We have easily created a Semi-raised planting bed. Be aware this will shift the soil in this planting bed up towards the top end, leaving a trench along the sides and at the bottom end, by design.[/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Standardised dimensions and access to plants” collapse_text=”+ Standardised dimensions and access to plants” inline_css=”font-size: 11pt;” ]Because the aim is to have each bed approx the same dimensions (1.8m x 3.8-4m or 5.5 paces x 13 paces) this means its easily scalable and interchangable for crop rotation. Also narrow paths between beds gives us easy access to both sides of the planting bed.[/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Paired bed concept, light / shade, damp / dry ” collapse_text=”+ Paired bed concept, light / shade, damp / dry ” inline_css=”font-size: 11pt;” ]By growing plants in vertical paired-rows means the shaded band of soil between the plants acts a leaf shaded moisture retaining zone. The outsides of the paired bed each get half a days sun which is the drying zone.  This will cause water to be pulled through the mound of soil, drawing nutrients across the plants roots. Obvisously this mainly applies to the larger plants.[/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Design improves water conservation ” collapse_text=”+ Design improves water conservation ” inline_css=”font-size: 11pt;” ]Because its a sunken planting bed with un-dug compacted soil sides, water will drain into rather than away. At the bottom end of this planting bed there needs to  be a drainage trench area. see profile diagram[/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Slightly oversized bed to start ” collapse_text=”+ Slightly oversized bed to start ” inline_css=”font-size: 11pt;” ]At 1.8m or 5.5 paces in width the planting bed is a little wider than normal but this is because we are going to pull up the soil from the sides to create our semi-raised mounded bed once we start planting out. This will create 4″ wide drainage channels along the sides and at the bottom end of the bed.[/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Clump planting concept ” collapse_text=”+ Clump planting concept ” inline_css=”font-size: 11pt;” ]Basically rather than sow a long single row of seedlings we use a 3 pronged rake drawn across the back half of our 4 foot rectangular mound of soil. Then sow half of your seed packet into these 3 trenches. All sown from one single position.[/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Mounding the soil for each clump within the planting bed ” collapse_text=”+ Mounding the soil for each clump within the planting bed ” inline_css=”font-size: 11pt;” ]For each Clump plant groupings we are going to draw up the soil into a mound within the planting bed. Again the top of this mounded soil will be level with the height of the sunken tyre. Might be a good idea to spread out fresh manure in the drainage valleys between clumps towards the end of the growing season for the worms to break down. [/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Planting beds are isolated from each other, disease control ” collapse_text=”+ Planting beds are isolated from each other, disease control ” inline_css=”font-size: 11pt;” ]When I have experienced Blight it appeared to move fastest when plant roots share soil. Because of the compact soil barrier between beds plant types are isolated from one another. [/bg_collapse]

[bg_collapse view=”link” color=”#4a4949″  expand_text=”+ Grass borders between blocks of planting beds” collapse_text=”+ Grass borders between blocks of planting beds” inline_css=”font-size: 11pt;” ]Each 3block of planting beds is separated by 3ft grass paths. This help keep the natural level of your plot as well as being a reservoir for worms. Grass paths soak up heavy rain easily and the grass cuttings can be used as a mulch. [/bg_collapse]

Negatives (Cons)

[bg_collapse view=”link” color=”#4a4949″  expand_text=”- Soil is wetter for longer at start of season” collapse_text=”- Soil is wetter for longer at start of season” inline_css=”font-size: 11pt;” ]Because it is a well dug over and sunken planting bed with compacted soil walls. Over the winter the planting bed can become saturated with water and take longer to dry out especially if it is a wet winter during Feb and early March. Green manuring the vacant beds from late Sept to overwinter does reduce the water saturation. Dig over the bed in late February into slither clods using a sharp spade and cover with a clunnel to speed up the drying out of the soil through wind channeling. .[/bg_collapse]


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Sun goddess wall sculpture

This growing system is the culmination of 5 years of experimenting with planting bed orientation and design at my allotment plot. After being dismayed at the sketchy information about this most crucial point for a new starter whose very first questions are Q:1# How do I set out my plot ? What; where, how, should I dig ?

The best book I found was the concise “How to Garden” (2009) by Alan Titchmarsh, he at least attempts to explain various growing systems (page 18) and also mentions the easier Semi-raised’ digging concept that is used in this system. It sort of feels that vegetable growing on allotments is stuck in a “DIG FOR VICTORY” mentality with its fully open-soil farming inspired techniques from 1940 and plant spacing giving every plant full sun.

Sunken tugboat planting beds are all about maximising growth for plants that have a high water and nutrient demand due to deep roots, bushy growth and heavy cropping. Such as aubergines, chillies, tomatoes, courgettes and potatoes.

My plot in Essex is heavy clay that settles within a few months into a heavy claggy root suffocating type consistency. This is the reason unfortunately that the soil has to be dug over to dry out.  A main aim with this planting system is to try to reduce the soil settling especially during the crucial root developing early months (March – April – May).

When Sunken tugboat planting beds are used in combination with my Clunnel cloche design (link) and a clump seed sowing approach successes become achievable.

Another important aim is to only use the soil from your plot and work towards improving it by dressing using bedding-heavy acidic horse manure to try to reduce the alkalinity of the clay soil and which will increase the yields as well as the range of vegetables that we can successfully grow. Also it avoids the physical hardship of wheelbarrowing or carrying imported soil bags across the site to your plot.

On the sew-saw of work over success we want medium effort but we want to maximise our planting successes and yield. Initially there is a lot of effort in the first year but going forward into the second and consequent years the effort is reduced considerably with this system and hopefully less disenchantment for new starters by taking the guess work out of veggie growing. Other considerations are ‘low cost’ (FREE) and upcycling skipped materials (pallets; tyres & block paving bricks) as well as being easy to construct by persons of all abilities with basic tools.

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