How to Build an EcoPropagator

Latest Update: 3rd March 2018.

An EcoPropagators allows the gardener to maintain a reliable supply of healthy seedlings and cuttings throughout the year.  It provides protection against insects, extremes of weather and delivers a constant supply of nutrients and water to the plants' roots. 

The EcoPropagator is a mini Ecobed sat inside a protective enclosure.  It uses a subsoil tank to supply water as required, and the soil is 100% compost.  The compost is homemade and biologically active.  

By sowing seeds in plastic mini pots up to their rims in this soil, germination rates are quick and secure.  I rarely get a failure, which means I only need sow one or two extra seeds to ensure I get all the seedlings I need.  Similarly when transplanting the seedlings individually into small fibre pots, I rarely have a failure.  Because of this, I don't need to grow large numbers of seedlings to guarantee success in my EcoPropagators.  When the mature seedlings are planted out into my Ecobeds (in their fibre pots) they establish themselves very quickly without exception.


This page takes you through the process of making an EcoPropagator, and I trust you will find as I did that the resulting device will become a vital tool in the process of growing strong healthy and tasty vegetables in your veggie patch.

This sketch shows the left side panel (looking at it from the front of the assembled unit).  Its made from 9mm marine ply cut to the dimensions shown, with a 50mm hole cut using a hole saw (centred 60mm from the side and 130mm from the top corner of the panel).  The swiveling vent cover is also made from 9mm marine ply and is 70mm in diameter.  A tight fitting 30mm long stainless steel M6 nut, bolt and (3)washers, supports the swivel vent and holds it in place.

This vent is used when daytime temperatures are very warm, but night time temperatures are still low in Spring.  The vents are closed at night for protection, and opened during the day to allow accumulated hot air to escape.

The sketch asks you to imagine you can see through the side panel to the ends of the front and rear panels and the side of the cover.  It's drawn like this so you can see how the front and rear panels will be positioned when the unit is assembled.  It also shows how the cover panel sits on the front and rear panels, and how a timber block stops the cover from sliding off the unit.

The side panels are painted before assembly with a water based weatherproof acrylic paint. (2 coats)
The front and rear panels are also made from 9mm marine ply, and the 19 x 42mm pine braces are cut to size and screwed into place using 35mm galvanised button head screws.  They are painted after the braces are fixed, but before the unit is assembled.
The EcoPropagator is assembled with the braces on the outside of the unit so the inside is flat enough to fit the polythene tank liner.  The Button head screws are on the inside and are screwed through the marine ply into the pine bearers (screw heads shown above).

The cover is made from 19 x 42mm untreated pine, and after cutting to length the components are screwed together as shown above using two 75mm countersunk galvanised wood screws at each joint. It's best to pre-drill the holes for these screws because there isn't much space, and you must avoid splitting the timber.

Two screws are needed in each joint to keep the frame flat, but only two 35mm countersunk galvanised wood screws are needed to hold each stop in position, and there is no need to pre-drill the holes for these screws.

Paint the assembled frame with 2 coats of weatherproof water based acrylic paint.

The sketch shows the screw positions needed to secure the polycarbonate cover (winter use). Twenty-four 15mm galvanised button head screws are needed to hold the plastic sheet flat enough to keep insects and extreme weather out of the EcoPropagator.

In warmer conditions Vegenet replaces the polycarbonate cover using four 30mm galvanised bullet head nails as hooking points (one in each corner) to hold it in place. It keeps airborne pests out and reduces sunlight intensity by over 20%.

The extra lengths of each leg of the cover frame at the top and bottom are handles designed to make it easy to take the frame off the bed and replace it later. The stop locates the frame so that the cross members line up with the top of the front and rear panels to seal the unit from insect penetration and drafts.
Here is one of the button head screws holding the polycarbonate cover in place.
Here is Vegenet held in place tightly over the EcoPropagators cover frame using 4 bullet head nails as anchoring points.
The whole area inside the cold frame can be used for propagating by using 2 layers of 200 ┬Ám plastic sheet as a liner for the water tank.

The plastic liners (which rest on the ground) are suspended in position by stapling them along their top edges to the walls of the propagator.  The design of the filling, distribution and overflow unit is similar to that used in full sized Ecobeds.  The water tank depth is 160mm which is plenty because seedlings take up far less water than mature plants.
This picture shows the tank being filled with rainwater and Scoria.  When the water starts to overflow through the overflow tee section turn the supply off.  More Scoria is added until it is level with the water.

A piece of horticultural fabric is placed over the Scoria and cut 25mm oversize on each edge so it can be turned up the sides of the unit to seal the tank when the soil is added.
A high carbon content soil (100% sieved homemade compost) is added to the bed.  This wicking medium stays moist at all times as water is wicked up from the water tank.  Up to 90 mini pots and small jiffy (fibre) pots containing seedlings growing in organic potting mix are buried up to their rims so that moisture and beneficial microbes can migrate from the biologically active soil into the seedling's root zone.  Here the microbes quickly establish symbiotic relationships with the seedlings.  The compost's constant moist state could become anaerobic if not replaced from time to time, and to avoid this, I replace the soil and the horticultural fabric every 3 months.  The compost is recycled through my composter where high temperatures destroy any developing plant pathogens.
I need to leave the Eco Propagator's polycarbonate cover in place during early spring to protect tender young seedlings from cold, windy conditions at night, but during the day temperatures swing the other way and sometimes the propagator gets quite hot.  I open vents installed in the top corners of the propagator to remove hot air during the day.   A VegNet filter is stapled over the opening inside the propagator.  It keeps insects out when the vents are open.