UK Garland examples / Decision guide
Heated propagator controls: no thermostat, fixed or adjustable?
A UK buying guide to temperature control, using Garland’s G51 Super 7 and G78 Big 3 as documented examples. Checked 15 October 2026.
Choose a propagator by the temperature control you need, not just the word “heated”. A non-thermostatic unit adds heat without maintaining a chosen target. A fixed thermostat has a manufacturer-set target. An adjustable thermostat lets you select one within its supported range.
For the two Garland models compared here, the distinction is specific:
- G51 Super 7: no thermostat; Garland describes an increase in ambient compost temperature of around 8°C.
- G78 Big 3: a built-in fixed thermostat designed to maintain compost at 19°C.
Those are different kinds of specification. Neither means you can select any temperature you like. Garland G51, Garland G78.
If a supplied leaflet requires a controller that is missing, do not use the propagator until the seller or manufacturer has resolved the mismatch for your exact unit. A general guide cannot establish that your box contains the correct equipment.
Start with the temperature your sowing instructions require
Find the germination or propagation instructions for what you intend to grow before choosing a control type. This guide does not prescribe a temperature for particular seeds or assume one setting suits every sowing.
Then ask two practical questions:
- Do you need a particular compost-temperature target, or are you looking only for additional warmth?
- Will you need to change that target between sowings?
If you cannot answer those yet, postpone the control decision rather than paying for a feature whose purpose is unclear. Keep the distinction between surrounding conditions and compost temperature in mind when reading both seed instructions and product descriptions.
No thermostat: additional warmth, not a selected temperature
Garland identifies the Super 7 as model G51. Its product page describes a 13 W heating element and explicitly says the unit is not thermostatically controlled. The approximately 8°C figure describes the intended temperature increase, not a fixed endpoint. G51 product information.
Here is a deliberately simplified illustration of the wording:
- An unheated compost baseline of 12°C plus an 8°C increase would be 20°C.
- An unheated compost baseline of 18°C plus an 8°C increase would be 26°C.
These are arithmetic examples, not measured G51 results or predictions for a windowsill. They show why a quoted increase cannot be read as a promise of the same final temperature in different conditions. Garland’s “around” also matters: the specification is not an exact eight-degree guarantee.
Consider this control type when additional warmth is the job. If maintaining a selected target is essential, the non-thermostatic specification does not satisfy that requirement on its own.
Fixed thermostat: check the target before buying
The Big 3 is model G78. Garland describes a 50 W heating element with an inbuilt fixed thermostat designed for a compost temperature of 19°C. Its automatic control is therefore different from a user-adjustable temperature setting. G78 product information.
A fixed-control model is a candidate when its documented target matches your intended use. If your sowing instructions require a different target, do not assume “automatic” means you can change it.
Treat the stated target as the manufacturer’s design specification, not evidence that every tray in every setting stays exactly at that temperature. We have not measured temperature stability or variation across either propagator.
Adjustable thermostat: verify the complete control package
An adjustable model is worth considering when selecting or changing a target is part of the job. Garland’s separately listed Professional Variable Temperature Control propagator, G193, is an example of a product supplied with a digital controller and a probe. It should not be confused with the G51 or G78. Garland’s variable-control product.
For whichever adjustable model you are considering, check:
- The supported target range and any restrictions on surrounding temperature.
- Whether the controller and required sensor are included in that exact package.
- Where the manufacturer instructs you to place the sensor.
- Whether the instructions match the model and version offered by the retailer.
A display is not enough evidence of adjustable control. Look for an explicit description of how the user selects the target. Nor does a heater’s temperature setting establish cooling capability if the chosen location becomes too warm.
Resolve a model or leaflet mismatch before use
Compare the model code on the unit, the box, the order confirmation and the leaflet. If they disagree, photograph them and send the seller or manufacturer a specific question: “Which instructions and included components apply to this exact model?”
Garland provides an instruction-manual page and directs customers to contact it when their manual is not listed. Do not treat another owner’s experience or a similar-looking product as confirmation that an instruction can be ignored.
Make the final choice in this order
First match the control type to the task. Then check the exact model code and included components. Finally, confirm that its dimensions and intended location suit the space you have.
Do not use wattage as a substitute for those checks: the number by itself does not identify whether the temperature is uncontrolled, fixed or adjustable. The G51 and G78 examples establish that their controls differ; they do not establish which propagator produces better germination, lower running costs or more reliable results.
Research note: This is a comparison of manufacturer specifications, not a hands-on electrical or growing test. No seed-specific temperature, electrical modification, add-on controller compatibility or adjustable-model temperature range is recommended here.