Having a beautiful lush green lawn creates a wonderful accent to any home and its living space. Trees, shrubs and ornamentals are eye catching, long-lasting additions to a landscape providing structure, shade and even fruit to a garden. However, to add health and vigour to these elements of landscape design, many things must be taken into consideration.
Lawns, trees, shrubs, potted and edible plants have different nutrient requirements for a healthy life. Does that lawn need to tolerate drought, shade and/or traffic? Will it grow in the region and is it high maintenance? In what soil type is it expected to grow? We also need to know what type of grass it is because each variety has different needs. Buffalo, kikuyu, couch and zoysia are the most common varieties in Australia.
Are the plants exotic species or indigenous to Australia? Are they shade lovers or drought tolerant? Will they grow big and overshadow the lawn and other plants?
Will they suck nutrients from the lawn? Are they high maintenance? What fertiliser will they need?
Just like all living things, plants and lawns need water. Once a week with a good soaking is all that is needed. Too much water leads to mould and poor root systems that will decrease their health over time.
The trick to a beautifully lush green lawn and outstanding plant specimens is the application of the right fertiliser at the right time. All fertilisers contain three primary nutrients that are always labelled on the packaging in this order: nitrogen, phosphorous and potassium (NPK).
TIP: Remember these letters by keeping ‘up, down and all-around’ in mind when reading fertiliser labels. The first letter promotes ‘up’ (rapid growth,) the second promotes ‘down’ (root development) and the third letter promotes ‘all-around’ (overall health).
Nitrogen (N) promotes rapid growth and lush green leaf; phosphorous (P) helps develop healthy root systems (starter lawn fertilisers have a high phosphorous count for this reason), and potassium (K) boosts the overall health of grass and plants and helps with disease resistance, drought protection, fl ower production and cold tolerance.
The NPK listed on a bag of any fertiliser indicates the percentage by weight of each of these three major nutrients. For example, a common type of all-purpose fertiliser is referred to as 10-10-10. That means the bag contains 10 per cent nitrogen, 10 per cent phosphorous and 10 per cent potassium. The remaining ingredients contain other nutrients and fi llers. Fertilisers for fl owers, trees, shrubs and edibles have different compositions to those we use on lawns so always use the correct fertiliser for the best results.
Even if proper nutrients are present in the soil, some nutrients cannot be absorbed by grass and plants if the soil pH is too high or too low. For instance, most plants require a soil pH of 6.5 to 6.8 to absorb phosphorus. A soil test is a great way to decide which of these ratios is needed in the highest amount. Inexpensive testing kits are widely available at garden retail outlets. If the reading shows it is below 5.5, add fertiliser with lime to lower the acidity and if it’s above 7, add fertiliser with sulphur to reduce the alkaline levels.
TIP: It’s best to raise or lower soil pH slowly over the course of a year or two and compost moderate soil pH whilst improving soil structure.
The most efficient way to broadcast fertiliser across lawns is to use a handheld or push-type mechanical spreader. Handheld ones are ideal for small lawns and covering patches.
The best time to fertilise lawns is in early autumn, which provides us with cooler weather and warm soil creating the perfect environment for grass to develop strong roots and grass seeds to germinate.
An application of nitrogen-rich, slow-release fertiliser will continue to feed the lawn and provide essential nourishment for the coming spring. This slow release also allows plant roots to harvest the nutrients they need slowly, preventing these necessary elements from leaching away into the soil. This type of food is easy to apply and minimises the chance of burning the lawn.
The next best time is spring – a well-balanced fertiliser in spring will produce a burst of growth and good colour. Avoid laying and fertilising lawns in summer because of heat, drought, insects and increased foot traffic.
While most of the garden ‘goes to sleep’ over winter, vegetables, bulbs and flowering annuals will benefit from an occasional application of plant food. Granular fertilisers are popular due to the ease of application.
Liquid or water-soluble fertilisers are spread using a hose and provide a quick, effective way to introduce nutrients rapidly to the root systems.
Plants need regular feeding if they are to continue to grow strong and healthy.
Flowering plants and vegetables require feeding all year round because a lot of energy goes into producing flowers and fruit. Apply less in winter, more in spring.
TIP: Always water the lawn thoroughly after fertilising so that the nutrients soak into the soil.
Organic fertilisers stimulate beneficial soil microorganisms and improve the structure of the soil. Soil microbes play an important role in converting organic fertilisers into soluble nutrients that can be absorbed by plants. In most cases, organic fertilisers and compost will provide all the secondary and micronutrients plants need.
Australian native plants are very sensitive to artificial fertilisers, especially too much phosphorus, which will kill them. Check the NPK of the fertiliser – the phosphorous (P) level must be 3 per cent or less.
TIP: Fertiliser is like a medicine – the right amount works wonders, too much is lethal.
In autumn, fertilise Azaleas, Camellias, Rhododendrons, Gardenias, Magnolias, Daphne’s and Pieris using a fertiliser designed specifically for acid-loving plants
TIP: Add fertiliser to the holes when planting bare rooted trees and shrubs but cover with soil so the plant’s roots don’t come into direct contact with it.
Vegetables are hungry crops and will thrive if given a slow-release fertiliser two or three times a year. Other ‘greedy’ flowering plants, such as sweet peas, clematis and roses, will benefi t from a mid-summer ‘top up’. Sprinkle fertiliser around plants and water in. There’s no need to feed in late summer.
Pot-grown plants rely totally on us for food, therefore it’s best to use liquid feeds because it can be too easy to overdose with solid feeds, which can scorch their roots when applied to the surface. However, we can incorporate a slow-release fertiliser into our planting medium when potting up plants. Begin feeding plants growing in pots six weeks after potting or repotting. The amount of feed plants need varies according to growing conditions, size and speed of growth. Some people underfeed while others overdo it. Over-feeding does more harm than good. As a general rule start feeding in spring, perhaps once every two weeks. Feed weekly when plants are growing vigorously and the weather is warmer, rising to twice weekly for heavy feeders or fast-growing plants in large containers.
Words: Marc Wonder