How to Grow Plants 

When we grow plants in our gardens, or in pots, or indoors, or in greenhouses, or wherever, there are some general ‘rules’ about how to get the best growth. There are hundreds, or perhaps thousands of different plant species and varieties that are grown in home gardens including vegetables, roses, fruit trees, shrubs, annuals, grasses, etc. Here are the general ‘rules’ that you should think about whatever it is you are wanting to grow.

For more on house plant care see How to Make Your Houseplant Last

Make the Plant ‘Feel’ at Home

Plants have evolved to, or have been bred to, survive in specific climates and conditions. The first thing to do is discover where the plant originates and what the climate is there. Then you can try and re-create those conditions for your plant by selecting the place in your garden with the most similar conditions or change the conditions where you intend to plant. Most plants that you purchase in garden centres, nurseries and other stores in New Zealand will have been selected to be suitable to somewhere in the country. Read any labels on the plant and ask the store staff for advice on whether it will thrive in the conditions in your garden.

Consider

• Where is your plant from? Where did the species/variety originate? What is its natural habitat?
• Temperature and humidity – What temperature and humidity prevail in its normal habitat?
  • In New Zealand, we have climates that range from temperate to sub-tropical and from moderately dry to rain forest.
    On the Koppen-Geiger climate classification, most of New Zealand is of type Cfb (*Warm temperate, fully humid, warm summer) or Cfc (*Warm temperate, fully humid, cool summer).
  • Think about your geographical region and where in the world it is like.
  • E.g. Canterbury/Otago have temperate climates like north-west Europe.

See Map for other locations with a similar climate.

By Koppen_World_Map_Hi-Res.png: Peel, M. C., Finlayson, B. L., and McMahon, T. A.(University of Melbourne) derivative work: Me ne frego (talk) - Koppen_World_Map_Hi-Res.png, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=14786605

• You will find that most imported plants in nurseries and garden centres originate in those regions shown in green. The exceptions will be indoor or hothouse plants which come from more tropical or desert climates.
• Sunshine – How much direct sunlight does your plant get in its normal habitat?
  • Does your plant, in its natural habitat, live in open sunny places or under a dense canopy of trees?
  • Select a place in your garden that most closely resembles the light conditions of the plant’s normal habitat.
  • For new plants from nurseries and garden centres, you will find advice on the light conditions that your plant prefers on the label.
• Wind/Shelter
  • Plants from the deep forest are not likely to do well in exposed sunny or windy locations; find them a sheltered, shaded place in a corner of your garden.
  • Plants from seashores and open land will be evolved to withstand wind and can be planted where they are exposed; they may even be used to protect more sensitive plants.
• Soil drainage
  • Is your plant’s normal habitat a swamp, a sand dune, a rocky slope?
  • As far as possible, mimic the plant’s natural soil conditions in your garden; add sand and rocks to the soil where well-drained soil is its normal soil type, find damp areas for plants that prefer wet roots.
• What type of soil does the plant prefer? Do you have sand, loam, or clay soil?
  • All soils are largely made up of tiny mineral particles. The size of mineral most abundant in your soil determines whether you have sand, loam, or clay. This mineral composition of the soil is called the soil's "texture."
  • Sand particles are small but compared to other soil particles they are largest. The other two main categories of soil particles are silt, which is smaller than sand, and clay, which is still smaller.
    • Sand - Water and nutrients move through sand soils fast meaning both need more frequent replenishing. A handful of sandy soil won't clump or hold a shape when you press it.
    • Loam - These soils have a beneficial mix of all the mineral particle sizes.
    • Clay - Microscopic clay particles pack together tightly. Water and nutrients move into and through clay soils slowly. Clay soils are heavy, and you can easily form a ball or ribbon with a clump of moist clay soil in your hand.
  • Most soils are mixtures of all three particle sizes but in varying proportions. A predominance of sand particles makes a lighter, more open soil with good drainage and aeration; lots of channels for air and water circulation. Minute clay particles pack together tightly making a clay soil heavier, denser, and with less favourable air and water circulation.
• Soil acidity
  • Most garden plants prefer soil in the pH range from 5.5 to 7.0. If soils become too acidic (below 5.5) or too alkaline (above 7.0) many plants become unable to absorb nutrients from the soil and suffer nutrient deficiencies.
  • Check the pH levels that your plants prefer. Plants such as azaleas, rhododendrons, strawberries and blueberries prefer low pH acidic conditions of around 5.5 while honeysuckles, clematis, poppies, geranium and others prefer higher pH conditions of 6.5 to 7.0. Lawn grasses prefer pH between 6 and 7. Autumn or cool-season green, leafy vegetables, these green, leafy vegetables prefer soils with a higher pH, between 6.8 and 7.5.
  • Test the pH; There are many home garden pH test kits available in garden centres and hardware stores. Test the soils in various parts of your garden, do not assume it is the same everywhere.
  • Here are a couple of simple home tests that will indicate if your soil is too acidic or alkaline:
    • Add a few drops of vinegar to a tablespoon of dry garden soil. If it fizzes, your soil's pH is greater than 7.5.
    • Mix a pinch of baking soda to a tablespoon of moist soil. If it fizzes, your soil's pH is less than 5.0.
• Pests and Disease
• Ask if the plant is resistant to the pests and diseases prevalent in your area?
• Where possible chose plants that are resistant to pests and diseases.
• If the plants are susceptible, be pro-active and consider conditions where the problem is less likely.
• Most fungal diseases take hold more easily in damp conditions where roots and foliage stay wet longer. You can reduce the risks of many diseases by ensuring good airflow around and through plants and good drainage around roots.
• Plant Hardiness
• See here for a New Zealand map of hardiness zones.

This might seem like a lot to remember so print it off, or better still, join MyKiwicare and favourite the page  (click the heart ♥ icon at the top of the page). It will then be easy to find when you return to Kiwicare.

Get growing New Zealand!

*Full meanings on Koppen Map
Cfb = Temperate oceanic climate; coldest month averaging above 0 °C (32 °F), all months with average temperatures below 22 °C (71.6 °F), and at least four months averaging above 10 °C (50 °F). No significant precipitation difference between seasons.
= Subpolar oceanic climate; coldest month averaging above 0 °C (32 °F) and 1–3 months averaging above 10 °C (50 °F). No significant precipitation difference between seasons
Cwb = Subtropical highland climate or temperate oceanic climate with dry winters; coldest month averaging above 0 °C (32 °F), all months with average temperatures below 22 °C (71.6 °F), and at least four months averaging above 10 °C (50 °F). At least ten times as much rain in the wettest month of summer as in the driest month of winter (an alternative definition is 70% or more of average annual precipitation received in the warmest six months).
Cwc = Cold subtropical highland climate or subpolar oceanic climate with dry winters; coldest month averaging above 0 °C (32 °F) and 1–3 months averaging above 10 °C (50 °F). At least ten times as much rain in the wettest month of summer as in the driest month of winter (alternative definition is 70% or more of average annual precipitation is received in the warmest six months).

David Brittain
Kiwicare