Establishing grass seed
🎯 The Basics
The basic rule to remember is that seedlings need four things to germinate and establish, adequate temperature, oxygen, water and light, remove one and the seedlings will struggle.
⏱️ Timing
Weather conditions are generally at their optimum to establish grass swards during the spring and autumn. This is when temperatures are typically at their most suitable not too hot and not too cold and when we can expect some help from mother nature in terms of regular rainfall.
Perennial ryegrass which is the most used species for winter sports will germinate where soil temperatures are consistently around 7 degrees Celsius or above.
🗝️ Practical tips
👉 With the right technology grass can be established at any time of the year, think irrigation during the summer or grow lights and undersoil heating during the winter, however, spring and autumn offer the best chance where one or all of these resources are missing.
👉 If you don’t have access to irrigation seeding between mid-May and August is considered high risk and if conditions don’t fall in your favour you may struggle to germinate seed or lose seedlings post germination.
👉 Given the right conditions perennial ryegrass will typically germinate in 7-14 days.
📌 Preparation
- Grass seed needs adequate seed-soil contact to germinate this can be achieved through use of specialised seeding equipment or by the application of suitable materials such as sands and dressings either with or on top of the seed.
- Creating a seed bed through scarification or creating a tilth on bare ground can also help maximise seed-soil contact.
- If overseeding into an established sward gradually mowing the grass as low as practicably possible without leaving any surface debris will help to maximise seed-soil contact and avoid the need for mowing before the new seed is well enough established.
Irrigation
As we mentioned at the start of this resource water is one of the key pillars to germination and establishment, irrigation whilst a luxury for most in a grassroots setting is crucial to successful establishment in periods of drought or when seeding during the summer.
If you can, try and provide a means of watering the most heavily worn areas that are likely to be bare at the point of seeding. Do not over water as this will lead to a lazy, shallow rooting grass plant.
Pre-seeder fertilisers
Pre-seeder fertilisers are generally applied either prior to or shortly after seeding to support the establishment of new seedlings. Pre-seeder fertilisers typically contain Phosphorus to aid root development and accelerate root growth.
In the spring Potassium is also required for new root growth and often pre-seeder fertilisers will contain a good percentage of Potassium aswell as Nitrogen.
🗝️ Practical tips
👉 If you only have an adequate budget for 1 or 2 applications a year, try and choose a controlled or slow-release granular fertiliser that will offer several months steady nutrition a typical analysis for spring/summer usage might be 18-5-18 (N-P-K). If you can apply a dedicated pre-seeder followed by later applications 6-9-6 (N-P-K) is a very typical pre-seeder analysis.
👉 It is generally accepted that iron containing fertilisers (Fe) should be avoided when establishing new grass swards.
👉 Soil analysis is best carried out in late winter to determine what nutrients the soil needs prior to selecting a fertiliser. Please see our resource on Soil Analysis for more info.
Germination Sheets
Allowing oxygen, light and moisture to penetrate, these can be used to protect a seeded area, retain moisture and accelerate germination. They should be used for a limited period of time and removed once germination has taken place. Leaving them in place too long will increase the chances of disease developing.
If you are using them to protect an area until better established raising the sheets for part of the day and making sure they are left in place overnight might help to mitigate disease risk. A widely available alternative to dedicated germination sheets is scaffolding netting.
🗝️ Practical tips
👉 If you historically struggle to get your worn goal mouths to re-establish, consider giving germination sheets a try.
Mowing of newly sown areas
For the initial cut, it is better to use a rotary mower rather than a cylinder as these may pull out weak rooted grasses. Mowing blades must be sharp to ensure the mower cuts rather than tears the leaf.
Height before mowing is usually around 40mm, this allows better root development and generally means the grass is adequately established. Alternate direction of cut to encourage tillering. Never cut more than a 1/3rd of the grass leaf at any one time.
Methods of overseeding
Please see our resources on overseeding and overseeders
💡What can cause seed to fail to establish?
⚠️ Lack of moisture
⚠️ Too cold, most grasses do not grow actively below 5 degrees Celsius
⚠️ Frost! Air and ground frosts will damage new seedlings, check the risk of frost before seeding
⚠️ Waterlogging, in waterlogged conditions the grass cannot get the oxygen it needs
⚠️ Depth of seeding, seeds that are sown at too shallow or too great a depth will fail
⚠️ Soil fertility, there must be adequate nutrients to encourage growth and establishment
⚠️ Weeds will compete with seedlings for water, nutrients and light
⚠️ Mistimed application of chemicals, many selective herbicides and other chemicals suggest a buffer period prior to and after sowing grass seed, follow the product guidelines to avoid chemical damage to young plants.
⚠️ Pests, this might be in the form of birds eating the seed, rabbits or foxes digging at bare ground that has been seeded or larvae that can feed on the roots of grass plants
⚠️ Disease, a number of diseases can cause a disorder called “damping off” this can be diagnosed by rotten seed, patchy germination or rotting at the base of seedlings. To minimise the risk ensure correct sowing rates and avoid excessive fertiliser use at the point of seeding.
