Cold-seeding involves the process of introducing fresh seeds into an existing sward during late autumn or early spring, specifically when soil temperatures are lower than what's needed for immediate seed germination.
Cold-seeding is a technique used to introduce new grass seed to an established fine English lawn during the late autumn or early spring when the soil temperatures are lower than what's ideal for immediate germination. This method, well-established in the United States for increasing the survival rate of new seedlings, is also highly effective for maintaining fine English lawns in the United Kingdom. It serves to prevent the loss of recently established plants, a common occurrence when cutting heights are reduced too soon after establishment.
All Gardening's Lawn Plan service has been at the forefront of introducing cold seeding to the residential lawn market.
Timing plays a crucial role in cold-seeding. The best time for over seeding fine English lawns is when soil temperatures range between 16-22°C. In the UK, this means over seeding can take place between April and September, with the late-August or early-September 'renovation week' widely recognised as the most suitable period for introducing new grass varieties to fine English lawns.
While late summer over seeding offers advantages such as warm soil temperatures, rapid germination, and extended daylight hours for seeding and top-dressing, it also has its downsides. This includes the risk of poor survival rates due to aggressive management while seedlings are trying to establish or early reductions in cutting heights.
Cold-seeding, on the other hand, addresses these issues by postponing the over seeding of fine English lawns to the winter months (November to February). In the UK, there has been some scepticism regarding this approach, mainly due to concerns about harsh winter conditions harming the seed.
However, it's important to note that while some seed may rot in the temperate UK winter climate, the percentage lost is generally lower than typical seedling mortality rates when over seeding is done at the more traditional time. Additionally, colder conditions can break the dormancy of fresh seeds, enhancing germination rates, especially when using very fresh seed lots for fine English lawns.
Cold-seeding can be implemented as a standalone strategy where all over seeding work occurs during the 'off-season,' or as a complementary 'little-and-often' approach. In the latter, some seed is introduced during the traditional late-August/early-September window, and the rest is applied in late winter/early spring. This doesn't necessarily require using double the amount of seed; instead, two lighter over seedings could be applied.
Moreover, funds previously allocated for curative fungicides can be reallocated to increase the number of over seedings throughout the year, not only to enhance the playability of fine English lawns but also as a proactive measure for disease prevention. The accumulation of disease-resistant grasses can act as firebreaks between patches of infected areas, effectively halting disease outbreaks.
Cold-seeding during the cooler months allows a seed bank to develop, with seeds ready to germinate as soon as soil temperatures rise. This is particularly advantageous for grass varieties used in fine English lawns, which have a built-in dormancy period after ripening or harvest. It results in excellent germination rates in early spring, offering advantages such as maturing plants before they are subjected to low cutting heights and providing better resistance to fungal attacks during the 'fusarium season' in late summer and autumn.
The choice of high-tech drills is not critical for the success of cold-seeding. As long as the seed is evenly distributed into the soil surface breach (achieved through methods like micro-coring, tining, or groom lines), the seed will vernalise and be ready for germination once warmer spring conditions arrive. The winter freeze-thaw process can also aid in embedding the seed in the soil. Key considerations include ensuring good seed-to-soil contact and sowing the seed at the correct depth (2-5 mm) to allow the new plant to emerge before its energy reserves are depleted.
Cold-seeding requires less reliance on irrigation, as spring rainfall and residual soil moisture are typically sufficient to initiate germination once soil temperatures are adequate.
For optimal results, new seedlings in fine English lawns should receive proper nourishment. Seed applied during the winter will germinate and emerge as soil temperatures rise in the spring, coinciding with the application of early season fertilisers. Organic or urea-based nitrogen is recommended for even uptake and longer-lasting effects compared to synthetic, fast-release fertilisers.
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Phil - Founder of All Gardening