Build an EcoPropagator

Latest Update 5th April 2020.

Its mid winter, and not much happens in the seedling EcoPropagators at this time of year.

The furthest one has just been renovated, and the nearest one is new.  Between them they can propagate at least 180 seedlings at a time (more if some are sown in clusters). 

I cant keep up with demand during spring sowing with just one propagator, and occasionally at other times of the year, I need to take one off line for maintenance while the other looks after demand.

I have a third smaller unit dedicated to growing cuttings.

These are the components I use to build my EcoPropagator.  Detail drawings and explanations can be found below.

The components are painted with a light coloured, weatherproof acrylic paint.  I use 2 coats to ensure good protection from the elements.

The painted components are assembled ready for fixtures and fittings, which are added next.  The cover frame receives its plastic cover, the details of which are described in the schematic drawing at the bottom of the page.

I apply the self adhesive copper tape around the bottom of the structure a side at a time.  I use the bottom external pine bearers to help keep the tape straight as it is applied, and apply the front and back first overlapping at the corners.  I then use the short tags of tape which go round the corners to guide the application of the tape on the other 2 sides.

Next I drill a 40mm hole for the overflow pipe.  It is set in the middle of the rear panel about 180 mm (centre) from the base.

The whole area inside the cold frame can be used for propagating by using 2 layers of 200 µm plastic sheet as a liner for the water tank.

The plastic liners (which rest on the ground) are held 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.

Scoria (crushed volcanic rock) is used to fill the water tank.  It is very light and porous and it shares the space with water, which occupies about half the volume.  Its main purpose is to support the soil above it separated by a light fleece membrane.  The Scoria allows moisture to rise from the surface of the water up into the soil by capillary action.

I add Scoria until it reaches just below the overflow pipe.  I then fill the tank until it starts to overflow.  I then gradually top up the tank with more Scoria until it is level with the water.  More water overflows as it is displaced by the additional Scoria and captured in a tray as shown above.  Eventually they reach equilibrium.

A layer of horticultural fleece is applied to keep the soil out of the water tank.  Note that the fleece overlaps the edges so they can be sealed against soil penetration.

The fleece is covered with a 60mm layer of sieved homemade compost which is used to make intimate contact with the soil in the seed tray cells.  A consistent supply of moisture and beneficial microorganisms is delivered, vital to the rapid establishment of healthy growth.

The water tank is filled through a vertical, rigid PVC pipe emerging from the compost.  The level indicator and blue cap on the top of the filler pipe need to be removed first.  This water handling system including the overflow has worked faultlessly since 2012 in my earliest Ecobeds.  The overflow, which connects directly into the filler pipe and cannot be blocked saves beds from flooding and indicates when a water tank is full during filling.  The overflow device is crude (table tennis ball on the end of a stick) but effective, and checking tank levels can be done while strolling around the garden.

This sketch shows the left side panel of the 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 high, 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 untreated 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 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.