How to Choose the Best Winter Lawn Fertiliser
A pristine lawn requires year-round care and maintenance, and a winter lawn fertiliser can help give your grass the boost it needs when the temperature drops.
It’s recommended that you fertilise your lawn at least twice a year: once in the spring, and again in the autumn/winter. Springtime fertilisers contain a different composition of nutrients to winter fertilisers, which is why it’s important to use different products. A winter lawn fertiliser will contain ingredients that have been specifically chosen to protect your lawn from harsh winter weather, helping to prepare it for growth in the springtime.
Choosing the best lawn fertiliser will depend on the current state of your lawn, as well as what your grass needs. We’ve put together the following information so you’ll have a better idea of what to look out for:
‘NPK Ratios’ – Why Are They So Important?
You may have seen the initials ‘NPK’ when looking at different fertilisers. These letters represent three elements. N stands for ‘nitrogen’, P for ‘phosphorous’ and K for ‘potassium’. These nutrients are vital for different stages of plant growth, and different fertilisers contain different ratios of them.
The ratio will be written as three numbers, for example: ‘NPK 6-5-10’. This fertiliser would be made up of 6 parts nitrogen, 5 parts phosphorous and 10 parts potassium.
Depending on your grass type, lawn condition, and the time of year, your lawn will benefit from higher concentrations of certain elements than others.
Below, you’ll find more details of each element and which part of grass development it contributes to. This will help you choose the right fertiliser, with the best NPK ratio, for your garden.
Nitrogen is pretty vital during all stages of a plant’s growth. It’s one of the main components of chlorophyll, which helps plants convert the sun’s energy into food. Chlorophyll is also responsible for giving plants their green colour, so nitrogen can help grass get greener and healthier.
Nitrogen is also important for a plant’s growth. Fertilisers that are applied at the start of the growing season, in springtime, often have a high ratio of nitrogen in order to encourage plants to grow.
Generally, it’s less important to feed plants high amounts of nitrogen during winter because the focus is not on creating growth spurts, but conserving strength and making strong root systems that will survive the winter.
Phosphorous also plays a part in helping plants to convert the sun’s energy into food and energy. It is particularly useful for improving the strength of a plant’s root system, as well as its stem.
Phosphorous is integral for general plant health; if plants aren’t healthy, they will grow slowly and take a long time to mature. Naturally, this will also make them weaker.
For these reasons, phosphorous is absolutely crucial to the development of grass. In some areas, the soil lacks phosphorous. In lawns, this will result in a weak root system and grass that will not withstand poor conditions – such as harsh winters.
However, too much phosphorous in soil can also be problematic. Phosphorous can build up in the soil, and excessive amounts reduce a plant’s ability to take other vital nutrients from the soil. This is one of the reasons why it’s important not to overdo it on the phosphorous front.
It is less common to find soil that is deficient in phosphorous than it is to find soil that is deficient in nitrogen. As a result, even some fertilisers that are aimed at winter use do not contain a high concentration of phosphorous (and some contain none at all).
As well as aiding with photosynthesis, potassium helps plants store and use water efficiently; it can help make them less susceptible to drought.
Also, similarly to phosphorous, it helps plants grow a strong, extensive root system – very important for helping grass to endure the harsh conditions of winter.
The Best NPK Ratio for Winter Fertiliser
A high nitrogen content is less important for winter fertiliser. However, grass still requires some nitrogen for promoting normal functions and it is not always present in the soil in high amounts – this is why most winter fertilisers still contain a reasonable amount of nitrogen. If you’re hoping to find a fertiliser that will be useful year-round, you will want a slightly higher ratio of nitrogen compared to if you’re using a separate fertiliser for winter and spring (recommended).
Not all fertilisers contain phosphorous, as too much phosphorous in the soil can actually build up and have a negative impact on the environment and plants. If your soil has a phosphorous deficiency, your grass will require a fertiliser with phosphorous. If not, you may want to avoid adding too much.
Potassium is an extremely useful nutrient, especially beneficial to grass over winter, because it helps grow strong roots and stems. Looking for a relatively high potassium ratio in a winter fertiliser is a good idea.
You may want to test your soil to find out what the current nutrient levels are, for a better idea of which what nutrients you need to add to the soil. There are several laboratories that you can send a sample of your soil to for testing. Remember that nutrients get used up, so the soil’s properties can change over time.
Liquid vs Granular Fertiliser
Fertiliser comes in either liquid or granular form.
Liquid feed is either a concentrate that can be added to water, or it’s pre-made. This fertiliser is generally fast acting and can be applied to the lawn using a watering can.
When using a liquid fertiliser, you want to make sure that it won’t get washed away before it has time to work. For this reason, liquid fertilisers can be better suited to summer rather than winter use – you’ll need a period without rain.
Granular fertilisers are applied dry and then watered into the soil. To apply a granular fertiliser properly, you should use a fertiliser spreader. These can either be simple handheld tools, or more complicated push-along/tow-along contraptions. Spreaders help ensure the correct distribution rate, which is a lot harder to calculate when spreading by hand.
Granular fertilisers are generally slow acting. They sit on the soil and slowly dissolve, gradually releasing the nutrients into the ground. They need to be thoroughly watered in order to dissolve. For this reason, it’s good to apply them when rain is forecast (which can be handy in winter). Otherwise, you’ll need to water the fertiliser daily until the granules are no longer visible.
With either fertiliser, you should avoid applying it on a windy day as this can cause uneven application.
Winter Lawn Fertiliser FAQs
When should I use my winter lawn fertiliser?
It’s best to apply winter fertiliser between early September and November. It makes the most sense to apply it around this time because you need to put it down whilst the grass is still growing. Once the temperatures go too low, the grass will go dormant and the fertiliser will have no effect.
Ideally, you want at least a month of active grass growth after applying the fertiliser, before the very cold temperatures hit.
In the UK, the colder temperatures are coming later and later. September and October are often very mild. This means you can sometimes get away with fertilising a lot later – even into December. You should still try to do it before winter fully sets in.
How do you apply granule fertiliser?
Granule fertiliser is best applied using a rotary spreader. You can also use a drop spreader, but you must be careful to get the rate of application right; if you get too high a concentration of fertiliser in one area, it can scorch the grass.
A spreader will have an aperture opening, which can be adjusted to change the rate of fertiliser application. A lot of fertilisers need to be applied at a concentration of 35 g/m²; however, this is not the same for all fertilisers and you should check the specific instructions carefully.
After spreading the granulated fertiliser at the recommended concentration, you will need to water it regularly. If it’s scheduled to rain over the next few days, you will not need to water by hand. Either way, you should keep an eye on the granules and make sure they are kept wet until they have entirely dissolved.
How long does fertiliser last in storage?
Depending on which fertiliser you purchase, it can last for several years in storage. As a general rule, try to use up any fertiliser within four years of opening it. Granules need to be kept dry, and liquid fertiliser needs to be properly sealed. Four years is a good guideline because the more time that goes on, the more likely the product is to become susceptible to damp or damage, especially as the packaging may start to degrade.