What fertiliser to use

Fruit, vegetables and flowers definitely respond to feeding, resulting in much more pleasure and satisfaction from your efforts. This page will assist you to choose the right fertiliser and advise where and when to use it. 

Which fertiliser to use

Which fertiliser to use depends mostly on where the plant is growing, (in the soil or in a pot) and whether the application is at planting time or a top dressing later to established plants.

-At planting time Trees, shrubs, roses, etc.

Novatec (controlled release over 4 months)

Ican Slow Food 24 month slow release

When applied at planting time, these fertilisers release the nutrients over a 4 – 24 month period, which gives plants a very good start. Because they release slowly, they are safe to use around the roots at planting time.

For top dressing existing gardens Trees, shrubs, roses, and fruit trees

Use Tui General Garden Fertiliser, Rose, Citrus, Acid, or Lawn as appropriate.

An alternative is Tui sheep manure pellets

For vegetable garden and flower beds

Use Ican organic Vege Food - Mix this into the soil prior to planting.

An alternative and also very good top dressing option is Novatec. Novatec is approximately 2.5 times more concentrated and is therefore used more sparingly.

Pots and containers - All plants

Use ican Slow Food (24 month) or Novatec, 3 times a year.

For a fast boost, use a liquid food like ican Fast Food Liquid Fertiliser

Lawns

Apply Tui Lawn Food three or four times a year. Be careful to apply evenly to avoid burning.

House plants - All plants

Use ican Slow Food

Use liquid food like ican Fast Food as a boost when required.

Liquid Feeding options

Liquid feeding of plants is useful for giving plants an extra boost. It is particularly effective for plants which are lacking vigour or recovering from a shock e.g. at transplanting time for seedlings, or for boosting yields e.g. tomatoes. Liquid feeding should be repeated 4 or 5 times at 2 weekly intervals. We recommend ican Fast Food liquid fertiliser

Organic manures

These are usually based on animal manure and in addition to supplying nutrients, they have a beneficial effect on soil structure, as well as supplying nutrients. Examples are Tui sheep manure pellets.

Nutrients required for growth

To be healthy and thriving plants require a balance of nutrients. (The exception being members of the protea family and some NZ natives which require only small amounts). Some soils, in particular sandy soils, require more fertiliser than clay soils.

The major elements required for plant growth are Nitrogen (N), Phosphorus (P) and Potassium (K). These are required in large amounts. Fertilisers which contain these three are sometimes referred to as NPK fertilisers (or complete fertilisers) and the percentage of each is referred to as the NPK content. A good NPK or complete fertiliser for plants in pots is likely to contain a ratio of 10%N 4%P and 8%K, while one for application to soils may contain a ratio of 6%N, 5%P, and 5% K.

In addition to the major elements, minor and trace elements are required. These trace elements are required by plants in very small amounts. In most soils these are available naturally in adequate amounts. However, they could be deficient in pot or container plants after a year or so.

Occasionally minor or trace element deficiencies show up in plants. Where this is suspected, bring a sample into a Green Door Team member.

Soil Acidity

The acidity of soil has an effect on availability of elements required for growth. Plants grow best in soils that are slightly acid. Fortunately most soils naturally fall in this band. Organic soils high in compost may be more acid and some chalk soils or clays may be too alkaline. If most of your plants fail to thrive and acidity is suspected seek advice from a Green Door Team member.

There are a few plants such as azaleas, camellias, rhododendron, and Daphne along with lawns, which prefer an acid soil.

Very acid soils are improved by adding Lime. Alkaline soils are improved by adding compost, sulphate of iron or sulphur.

Why do we use Lime?

There are three types of lime

• Garden Lime

• Dolomite Lime

• Gypsum

Garden Lime and Dolomite lime are both alkaline and are used to;

• Condition clay soils

• Reduce acidity

• Provide calcium

• Improve the availability of phosphate in the soil.

Gypsum is neutral and is used to,

• Condition clay soils

• Provide calcium

• Improve the availability of phosphate in the soil.

• Being neutral it does not affect acidity

Gardens benefit from an annual dressing of Lime, Dolomite or Gypsum. It improves the condition of clay soils and improves the availability of phosphate. This means that the other fertilisers applied will work better. However don’t over apply. Excess Dolomite application can lead to an over alkaline soil which suppresses potassium and other nutrients.

Use Gypsum rather than Lime or Dolomite on acid loving plants such as azalea, camellias and rhododendrons, and lawns.

Gypsum is a better safer alternative unless the soil is known to be acid.