Seedling heat mat, 25 cm wide, black with green markings, laid flat on a white background

Narrow-strip seedling heat mat, black with green markings, seen from above on a white background

Diagram of the two heated seedling mats with their dimensions, the power cable and the mat rolled up for storage

Cell tray of seedlings placed on a heat mat, with heat rising from underneath

Heating mat for seedlings

Name: Heating mat for seedlings
SKU: TC-SEMIS-10X52-EU
Availability: InStock

$23.00

$7.66 × 3 with no fees Klarna.

This heat mat, 52.5 cm long, slips under a row of pots or under your seed trays, and warms the grow medium from below. Choose the narrow strip for a windowsill, or the 25 cm mat for one to three germination trays.

Ref. TC-SEMIS-10X52-EU·Germination accessory

Size : 10 x 52.5 cm

10 x 52.5 cm

25 x 52.5 cm

Plug : Eu (230 v)

EU (230 V)

US (120 V)

Customer support 7 days a week by email

Delivery within 2 to 15 business days

100 % secure payment

The summary

What you receive: a heated mat 52.5 cm long, as a narrow strip or a 25 cm wide plate, with an EU or US plug.
Which width: the narrow strip for a row of pots on a windowsill, the 25 cm plate for one to three trays.
What it does: the base of the tray gains 5 to 11 °C over room temperature.
Getting it right: a probe thermostat controls the heat, which the mat supplies continuously.

Background heat for seedlings, in a narrow strip or a 25 cm mat, EU or US plug

This seedling heat mat is a flexible waterproof plastic sheet, 52.5 cm long, that sits flat under your pots or trays and warms the grow medium from below. A seed responds to the temperature of the soil around it far more than to that of the air, yet a tray left on a windowsill or a shelf often stays colder than the room. The mat keeps the base of the container between 5 and 11 °C above the ambient temperature, so that cold-sensitive species germinate without waiting for the season to warm up. Depending on the version you choose, its cable ends in an EU or US plug, which you connect directly to a wall socket.

📏 Two widths, one length

Choose the width according to the containers you will place on it, since the mat only heats what rests on its surface. Both sizes share the same length of 52.5 cm and the same cable of about 1.4 m, which reaches a wall socket at floor level. A tray that overhangs the mat keeps its outer cells cooler than those in the centre, and germination there is slower: so measure the base of your trays or the length of your row of pots before choosing.

Narrow band

It holds a row of small cups or germination plugs, and fits on a windowsill or a narrow shelf.

25 cm plate

It takes one 37 × 23 cm tray, or three small 19 × 14.5 cm trays placed side by side lengthways.

Same length

Both formats measure 52.5 cm in length, so a strip and a plate can be lined up on the same shelf.

🌱 Sowing on the mat

First prepare your pots or cells, moisten the grow medium, then sow and cover the tray before placing it on the mat. Tomato, pepper, aubergine and basil germinate best between 21 and 29 °C, so it is their late-winter and spring seedlings that benefit most, as do the herbs you restart indoors in autumn. On a windowsill at 17 °C, for example, the base of the tray settles between 22 and 28 °C, right within the useful range. The mat has no regulation and heats continuously: a probe thermostat, with the probe slipped into the grow medium, lets you aim for a precise temperature. Once half the seeds have sprouted, remove the lid and unplug the mat, as stated in the instructions printed on its surface. Cold grow medium is, incidentally, among the most frequent causes of germination failure.

A domed tray on the 25 cm plate

The 25 cm mat takes a 37 × 23 cm germination tray with its dome, leaving about 15 cm free along the length. The dome holds the heat supplied by the mat from below above the cells, so the grow medium stays at a steady temperature through the night. With 40 cells per tray, you can start a full batch of tomatoes or basil in one go, then crack open the vents as soon as the first shoots appear.

Continuous heating, never in full sun

Once its heating has stabilised, the mat reaches roughly 32 to 38 °C, and it does not switch off on its own. In direct sun or under a grow lamp, the grow medium then goes beyond the useful range and the young roots dry out: never use the mat in either of these situations. Check the temperature of your grow medium every day during germination, or entrust it to a probe thermostat. Store the mat rolled up and never folded, do not place anything hot on top of it, do not cover it with insulation and never get the plug wet.

🐟 Before transplanting in aquaponics

In an aquaponic system installed outdoors or in an unheated greenhouse, the water stays cool in spring, and a seed sown directly into the circuit germinates slowly. The mat lets you start the seedlings indoors, in peat germination pods or rockwool cubes, then transplant into the grow bed baskets plants whose roots have already emerged. Germination therefore takes place outside the circuit, and only a rooted plant joins the fish water. Do, however, keep the mat away from the bed: it warms a grow medium placed on top of it, not the water of a pond, and its plug must stay dry.

🫙 Other uses for the same mat

The mat is also useful beyond seedlings, whenever a container needs to stay a little warmer than the room. In the kitchen, it keeps a jar of kombucha, kefir or lacto-fermented vegetables gently warm, as they ferment slowly in a cold room, as well as bread dough that needs to rise. Finally, it speeds up the rooting of cuttings, whether they come from houseplants or the vegetable garden. In every case, the rule remains the same: the mat heats continuously, it is for indoor use, under supervision and out of reach of young children, and a probe thermostat prevents exceeding the desired temperature.

Technical specifications

The format

Dimensions: Narrow strip or 25 cm mat, 52.5 cm longTwo widths for the same length
Connection: EU 230 V or US 120 V plugPlugs straight into a wall socket, with no separate power block; choose the plug for your country, as the US version will not connect to the European mains

Heating

Temperature gain: 5 to 11 °CAbove room temperature, at the bottom of the container
Stabilised temperature: Around 32 to 38 °CTo be checked under a closed dome

The use

Regulation: None, continuous heatingA probe thermostat lets you aim for a set temperature
Cable: Approximately 1.4 mEnough to reach a socket on the floor

To budget for separately

A dome tray: 37 × 23 cm traysOne tray fits on the 25 cm plate
A thermometer: Thermometer and hygrometerTo track the heat and humidity under the dome

In the box

1 heated seedling mat, in the width of your choice, with its cable and the plug of your choice (EU or US)

Length, width of the plate, plug and material: product sheet and diagram. Temperature gain, stabilised temperature, cable and germination markers: instructions printed on the mat and product visuals, taken on 02/10/2026.

What width for your seedlings?

The same length of 52.5 cm, as a narrow strip or a wide sheet.

Narrow strip or wide sheet The width of the mat follows the containers placed on it.

	Format	Length	Receives	Tray of 37 × 23 cm	Price
Narrow bandYour choice	Narrow band	52.5 cm	a row of cups or plugs	No	$23.00
Recommended 25 cm plateYour choice	25 cm plate	52.5 cm	one 37 × 23 cm tray or three small trays	Yes	$32.00

Narrow band

The format

FormatNarrow band

Length52.5 cm

Receivesa row of cups or plugs

Tray of 37 × 23 cmNo

The price

25 cm plateRecommended

The format

Format25 cm plate

Length52.5 cm

Receivesone 37 × 23 cm tray or three small trays

Tray of 37 × 23 cmYes

The price

Length and width of the plate taken on 11/10/2026 from the product diagram.

Estimate your
delivery time

The exact shipping cost is calculated at checkout, based on the total weight of your order and the destination. Lead times start from dispatch and remain estimates. For a destination not listed here, write to us at contact@univers-aquaponie.com.

Frequently asked questions

8 questions

6 key questions, 8 in the detailed view

Which width should I choose, narrow strip or 25 cm sheet?

How many days do seedlings take to sprout on a heat mat?

Species	Emergence
Lettuce	3 days
Cucumber	4 days
Tomato	6 days
Aubergine	6 to 7 days
Basil	5 to 7 days
Pepper	7 to 10 days

These times apply to a grow medium kept between 21 and 29 °C, and they vary with the variety. Lettuce, which germinates poorly above 25 °C, generally does without bottom heat.

Do I need a thermostat with this mat?

How do you fit the mat under a seedling tray?

Can it be left plugged in day and night?

Can it be used for cuttings?

Do you need to water more often on a heat mat?

Can the pots be placed directly on the mat?