Growing Indoors - Light & Heat

Growing or Starting Plants Indoors - Light & Heat

The ability to start plants indoors means you can get started in late Winter/early Spring, much earlier than if sowing outside. However seedlings need to have adequate light and heat to grow into strong healthy plants, that's why using supplemental lighting and heat mats can be a good idea if your indoor environment cannot provide this.

Why use supplemental heat?

Most seeds need temperatures of 18°C to 20°C to germinate, with warmer climate crops such as tomatoes, peppers and aubergines needing 22°C. It can be hard to create a steady temperature in some houses during late winter/early spring. Therefore using a heat mat or heated propagator can allow you to sow seeds and raise plants much earlier than if sowing outside.

Why use supplemental light?

Seedlings need at least 12-16 hours of light each day. Most houses will not have enough natural light to accommodate this. Placing your seedlings in a window - even south facing - may not be enough to do the job. The quality of light on a windowsill is also not great as it is coming from an angle. Seedlings are likely to grow towards that light causing a leaning stem. Some people may turn the seedlings to make them grow straighter but this will usually lead to 'leggy' seedlings and they will struggle to grow into a strong plant.

If you don't have a suitable outdoor protected structure such as a polytunnel, greenhouse or cold-frame, it may be worth investing in some lights.

How to use lights?

Set up the lights as close as possible to the seedlings without touching them ( 2-3 inches). Make sure to alter the height of the lights as the seedlings grow. When seedlings first appear, keep the lights turned on for 12 to 16 hours per day. It's important not to leave the lights on full time as the seedlings do need a period of dark too. A timer on your socket is an easy way to control this.

Lighting

Duo LED Grow Light - Ideal for hobby growers, easy to set up in your kitchen. The Duo Grow Light with stand features a scientifically developed LED light with precisely those wavelengths that maximize growth. Perfect for starting off seedlings, growing herbs, wheatgrass and microgreens - especially in the darker winter months.

SANlight Flex II LED Grow System - Ideal for larger scale or more serious home growers. The SANlight II Flex series is a compact modular LED system which is ideal for layered propagation areas. The passive cooling system keeps the light cool when in operation. This, and the waterproof design, also allows the SANlight FLEX II to be used between plants where there is no light. They are often used in microgreen growing and for propagation of vegetable plants to supplement existing light. They are not powerful enough to raise vegetable plants without a reasonable amount of natural light also being present.

SANlight Evo Series 1.5 LED Grow System - For professional growers. The SANlight EVO-series is a powerful and highly efficient LED Grow Light. Perfect for the all-year-round production of microgreens, wheatgrass and salads as well as propagation of plants (tomatoes, cucumbers etc.) in early spring to for planting in a greenhouse. The light emits a full spectrum wavelength of between 400 - 780nm. Very close to sunlight, this is the light range plants use for photosynthesis and therefore the SANlight is suitable for all stages of propagation from vegetative to generative. These lights can be used to raise plants even when there is little or no natural light present, which may be the case when growing plants in insulated boxes for example.

Heating

Windowsill Propagators - Ideal for hobby growers. These compact electric propagators are a complete nursery for the windowsill. Supplied with seed trays with high dome propagator lids. We have 7 tray and 3 Tray options available.

Biogreen Propagator - Very useful covered propagator for starting your plants in Spring. Heated version comes with a strong UV stabilised clear cover and a 1.2m x 0.5m Heating Mat (150W) with remote soil sensor and thermostat. Temperature range 0-40°C.

Heating Mats - Ideal for larger scale or more serious home growers. Heating mats are an alternative to soil warming cables: they consist of a special resistor cable, covered with a safety Teflon coating, stitched on a sturdy matting and finally covered with a strong protective aluminium foil. Their main advantage is that the can be easily rolled up and stored if the shelves/benches are needed for other purposes. These mats include a temperature sensor and a thermostat for precise heat control.

Soil Warming/Heating Cables - Ideal for professional growers. With this range of flexible silicone covered electric soil warming cable you can build a propagator to the exact area you need. However, there is a bit of work and extra materials involved as a box with sand needs to be constructed for housing the cable. We provide more detailed instructions on constructing a propagation box in the product details. One or more cables can be plugged into a thermostat for temperature control.

Browse our full range of propagation equipment here.