The Importance of Seed Starting with Heat Mats and Grow Lights

The Importance of Seed Starting with Heat Mats and Grow Lights in Scotland’s Winter Months

Scotland’s long, dark winters and unpredictable weather make gardening a challenge, particularly for those who want to start seeds early in the season. With short daylight hours, cool temperatures, and frequent frost, traditional outdoor sowing is not feasible for many crops.

This is where seed starting indoors, with the help of heat mats and grow lights, becomes essential. These tools provide the warmth and light necessary for germination and healthy seedling growth, ensuring a strong start to the growing season. We don’t really have Zones in the UK but we would be a Zone 7.

Overcoming Scotland’s Cold Winters

Limited Growing Season

Scotland has a short growing season, with the last frosts often lingering well into May, particularly in northern regions and highland areas. We are South East in Scotland and we usually get last frosts until around the 15th May. Without indoor seed starting, many warm season crops, such as tomatoes, peppers, and aubergines, wouldn’t have enough time to mature and produce a good harvest before autumn frosts returns again.

By using heat mats, seeds can be started as early as January or February, allowing gardeners to grow a much wider variety of crops than they could by relying solely on direct outdoor sowing.

This year we have invested in the start of the season equipment. We have the raised beds and fruit trees set up, but we want to grow a bigger variety of foods. As always windowsill growing works great, if you have a warm south facing one, especially with a foil backdrop to use up every bit of the sun rays, but it’s not enough for ALL seeds to get started as the Winter sun just isn’t enough.

Cold Soil Temperatures

Most vegetable and herb seeds require soil temperatures of 18-25°C (64-77°F) for optimal germination. However, in Scotland, unheated soil temperatures can remain below this threshold well into spring. Even in greenhouses or polytunnels, night time temperatures can drop significantly, slowing or preventing germination altogether.

A heat mat provides consistent bottom heat, ensuring the soil remains at an ideal temperature for quick and even germination. Without this added warmth, many seeds either fail to germinate or take significantly longer, delaying the entire growing process. We grabbed a small set of 2 from Amazon for under £26, they are an investment for future growth but keep within your own budget. This is our 6th year growing and we haven’t had them up to now and produced a large range of harvest, we are just looking to expand our variety with seeds that need more attention in our short growing season.

Compensating for Low Light Levels

Short Daylight Hours

From November to February, Scotland experiences very short daylight hours, with some northern areas getting as little as six hours of daylight per day. Many seedlings require at least 12-16 hours of light daily for strong, healthy growth.

Without sufficient light, seedlings become leggy and weak, as they stretch toward the nearest light source. This results in fragile plants that are more prone to disease, pest damage, and transplant shock.

From My PDC PRO Permaculture Design Course PRO 150 Page Portfolio showing the Summer & Winter Sun Patterns In Our Garden

Grow Lights as a Solution

Grow lights provide the necessary intensity and duration of light for seedlings, helping them develop strong stems and lush foliage. By using full spectrum LED or fluorescent grow lights, seedlings receive the correct wavelengths of light needed for photosynthesis, ensuring robust growth even in the darkest months. Again we picked up a 3 light set for around £23 from SeedFolk

Grow lights should be placed 2-4 inches above seedlings and adjusted as they grow. Without this artificial lighting, indoor started seedlings are unlikely to produce great plants in Scotland’s winter conditions for some seeds that need this extra heat and light to grow.

Faster, Healthier Germination and Growth

Speeding Up Germination

Heat mats create a warm and stable environment for germination, significantly reducing the time it takes for seeds to sprout. For example:

Tomatoes normally take 7-14 days to germinate in cool conditions but can sprout in 3-5 days with a heat mat.

Peppers often struggle in cold soil and may take 3 weeks to germinate naturally but will sprout in 7-10 days with bottom heat.

By reducing germination time, seedlings have more time to mature before being transplanted outdoors, leading to a longer and more productive growing season.

Preventing Weak and Leggy Seedlings

Without sufficient warmth, these seedlings often grow slowly and weakly, making them more vulnerable to damping off disease (a fungal disease that kills young seedlings). Heat mats ensure that seedlings grow quickly and evenly, while grow lights provide the necessary energy for strong stem and leaf development.

Again just stressing that this is just for certain seeds and not all. Majority of our seed starting doesn’t happen until around Easter time mid March to beginning of April giving seedlings 6-8 weeks of indoor growth before being planted outside mid May after the frosts have finished.

Growing a Wider Variety of Crops

Expanding Crop Options

Without indoor seed starting, Scottish gardeners would be limited to hardy, cold tolerant crops like kale, onions, and broad beans. However, by using heat mats and grow lights, gardeners can successfully grow warm season crops such as:

• Tomatoes
• Peppers (bell, chillies, and sweet varieties)
• Aubergines
• Basil and other tender herbs

This expands the range of available homegrown produce and allows for earlier harvests in the summer.

Overwintering Tender Plants

In addition to seed starting, grow lights and heat mats can be used to overwinter tender perennials like chilli plants, micro citrus trees, and lemongrass. Keeping these plants in a warm, well lit indoor space ensures they survive the winter and thrive again in the following season.

Maximising Space and Efficiency

More Control Over Growing Conditions

By starting seeds indoors with heat mats and grow lights, you have greater control over temperature, light exposure, and humidity. This eliminates the uncertainty of unpredictable Scottish weather, allowing for a more consistent and reliable start to the growing season.

Efficient Use of Space

In Scotland, where outdoor growing conditions can be harsh, using indoor space efficiently is key. With a heat mat and a set of grow lights, even a small windowsill, shelf, or indoor greenhouse can be transformed into a productive seed starting station. We use all our windowsill space and also have some shelving from Ikea with the added £3 cover this year that sits on our dinning table next to the windowsill where the seed trays are packed into at night with heat mats and lights. They are for outdoor use so will be used as a cold frame outside when weathering our seedlings, then dismantled and slid away until next year.

Cost Savings and Sustainability

Saving Money on Store Bought Seedlings

Purchasing seedlings from garden centers can be expensive, especially for specialty or heirloom varieties. Starting seeds indoors allows gardeners to grow a wider range of plants at a lower cost while ensuring they are organic and chemical free.

Avoiding Single Use Plastic

By growing seedlings at home, gardeners can use recycled seed trays, biodegradable pots, or soil blocks, reducing reliance on plastic seedling trays and commercial packaging. This makes seed starting not only cost effective but also more sustainable.

Best Practices for Using Heat Mats and Grow Lights

To get the best results from indoor seed starting, follow these guidelines:

Using Heat Mats Effectively

Place the mat under seed trays for consistent bottom heat.

Use a thermostat to maintain the ideal temperature.

Once seedlings emerge, remove them from the heat mat to prevent legginess.

Using Grow Lights Correctly

Keep grow lights 2-4 inches above seedlings and adjust as they grow.

Provide 12-16 hours of light per day to mimic natural sunlight.

Use a timer to maintain a consistent light schedule.

Other Tips

Keep humidity levels balanced to prevent damping off disease.

Use a gentle fan to improve airflow and strengthen seedlings.

Harden off seedlings before transplanting outdoors by gradually exposing them to outdoor conditions over 7-10 days.

For gardeners in Scotland, seed starting with heat mats and grow lights is essential for overcoming the challenges of the cold, dark winter months. These tools provide the warmth and light needed for strong germination and growth, ensuring a productive and extended growing season.

By starting seeds early indoors, you can grow a wider variety of crops, enjoy earlier harvests, and save money, all while increasing sustainability and food security. Investing in a simple heat mat and grow light setup can transform your gardening success, making it possible to grow healthy, vigorous plants no matter how harsh the winter may be.

For The Rest Of The Seedlings: How To Stop Leggy Seedlings With A DIY Foil Seedling Backdrop On The Windowsill

Happy Gardening!

Katrina & Clayton and family live in East Ayrshire and share their daily life in the garden on instagram. They practice permaculture principles in the garden, reducing & repurposing waste whenever they can. Katrina shows how home educating in nature has helped Clayton thrive. 

Clayton Completed The 2 Grow and Learn Courses with the Royal Caledonian Horticultural Society. He is Autistic, Non Verbal & has been Home Educated since 2018. Katrina & Peter hold their PDC & PDC PRO Permaculture Design Course from Oregon State University 

They featured on BBC Beechgrove Gardens Ep23 2022 and returned in 2023 for an update, Katrina & Clayton are also columnists for ScotlandGrows Magazine, Guest Blog for Caledonian Horticulture as well as working with Gardeners’ World Magazine and many other brands. 

They are also Author of the new Children’s Book Series: Clayton’s Garden Journey: Stories of Autism and Gardening. Topics on Growing, Harvesting, Sowing & Composting and 108 Page Weather and Seasons Weekly Gardening Record Book available on Amazon and Kindle. Listen in on their Guest Podcasts to learn more about them.

Our Children’s Book Series

Author of the new children’s book series: Clayton’s Garden Journey: Stories of Autism and Gardening. Topics on Growing, Harvesting, Sowing & Composting and 108 Page Weather and Seasons Weekly Gardening Record Book available on Amazon and Kindle

Visit Our Print On Demand Stores 

REDBUBBLE STORE -WORLDWIDE
Over 175 Garden & Nature Designs. Coasters, Phone Covers, Bags, Mouse Mats & Much More

---