Tips to improve the likelihood of survival

Follow the four basic steps of – plan, prepare, plant, protect – for a successful native garden.

Before you begin planting out, why not spend a bit of time first working out how it will look when the plants are fully grown? Getting things right and ready at the beginning will produce the best results. Follow the four basic steps of – plan, prepare, plant, protect – for success.

 

 

 

 

Plan

Visit a nearby reserve or a patch of native forest and look at the planting associations (how the heights, colours and shapes of the different species work together). Choose an area of your garden where native plants can grow to full height without blocking long term sun or views, or interfering with power lines, driveways, etc.

Draw a plan of the area you want to plant showing existing trees, paths, underground services, overhead power lines, etc. Try to picture your native garden in five to ten years time. How big will each tree or shrub be? Then think about other native plants that you would like to plant when the canopy above will provide frost and wind protection to other species, such as ferns and frost tender plants.

Place your plants in groups with a spacing between the larger trees of 2.5 metres - 3 metres, and between the small trees, shrubs and herbs of 1.5 metres - 2 metres. The final plan should show the name and location of each plant. This will help you to place your plants at planting time.

 

Prepare

You will need to prepare the site well to ensure plant growth and survival. This should be done some time before planting. For the average home garden situation, removing the grass cover will be best in the long term.

Mark out the area to be planted, lift turf out by cutting 1.5 spade widths wide (place cut pieces outside the area), use lifted turf squares for composting or cut them in half and place them inverted around the trees after planting, add well rotted manure or compost, aerate soil by forking or digging, keep the site weed free until planting time.

 

Plant

The best times of the year for planting are during the autumn months of April to May or late winter - spring (August - September). Planting outside the cooler winter months means that a lot of watering may be required to keep plants alive. Planting should be not be done on bright sunny days or very windy days in case plants dry out.

Before planting make sure that the site is moist but not water saturated, keep the plants cool and moist until you are ready to plant, mark with a stake where the plants are going to be planted, dig a hole wide and deep enough for the plant's roots to spread out, remove plants from their container, if the roots are evenly spread, place plants straight into planting hole (or cut the root ball with a knife down the length of the roots). Cover the roots with fine soil, firming layer by layer. Plant at same depth in the soil as the soil line at the base of the stem. Leave the surface with a loose texture and water thoroughly.

 

Protect

Mulching: Native trees and shrubs grow naturally with a deep litter mulch of decaying vegetation, such as old leaves, covering the ground around them. After planting, spread out wet newspapers, cardboard, old carpet (wool) etc. and cover with wet straw, bark chips (untreated) or compost to 90 -120 mm depth. This will protect roots, trap moisture and control or suppress weeds. Keep mulch away from the stems of the plants.

Watering: If planting practices have been followed and mulch applied, watering will only be necessary in dry, hot conditions. Watering should be done thoroughly but not often (once a week maximum).

After care: Until the plants are established (2 to 3 years) and start shading and covering the ground, it might be necessary to control weeds and replace mulch. Once cover is established and it is no longer necessary to weed, spontaneous germination of natives might occur. When the planted trees and shrubs have reached sufficient height and spread to provide shelter and shade (approximately 3 years), more tender plants can be planted underneath.

 

Dealing with Clay Soil

Working clay ahead of planting: Autumn is the best season because the soil is warm, moist with the rain and you can walk across the soil without it being muddy and in danger of compacting under your gumboots. Generally, areas that have not been planted will be a hotchpotch of weeds that colonise easily in clay. They will have well established tough roots that are not easy to remove, because difficult growing conditions attract hardy plants.

It is sometimes easier to spray off the area with glysophate (and a fixing agent to aid penetration) to get a broad coverage to kill off the weeds. With areas that have been left for some time, a second spray will be beneficial.

During this time you can apply gypsum to the surface area. Gypsum is a naturally occurring mineral, Calcium Sulphate, which loosens compacted soil, with no negative impacts on soil pH. (it is also the white product between the paper coating of Gib board). Gypsum is most often available in powdered or granular form and can be spread over the area at the specified rate. After rain, the soil can be dug over with some compost and an optional second application of gypsum. Depending on how far into the dirt you can dig, either leave it to soften a bit longer (more rain required) or begin to dig holes for plants.

Planting into clay soils: The general rule of thumb for planting it to dig the hole to the depth of the rootball (pot) and twice the width. It is important that all the rootball goes in the hole as plants with exposed roots tend to stress and die.

Place a handful of gypsum at the base of the hole and add a handful of compost or Garden Mix, before setting the rootball on top. Gypsum will continue to open up the clay for the roots and the growing media offers some extra nutrients. Some landscapers place special fertiliser tablets in planting holes at this time to add additional food, although it is not essential for most plants suited to growing in heavy soil.

Before placing the rootball of the plant in the hole, it is important to check the plant roots. If there is a mass of roots and very little potting mix, breaking up the root ball with hands or a knife prior to setting the plant into the hole helps to encourage root growth into the surrounding soil. If you don’t do this, the roots may be so compacted from growing in a confined space that the roots will not extend outwards and grow. Never place a dry plant in the hole – if necessary, soak it first in a bucket of water until the bubbles stop rising.

Placing soil and compost or Garden Mix around the plant is probably the most important part of the process. Digging a hole in clay soil, even if you’ve worked the top area, still leaves the possibility that the hole could become a water reservoir in winter rain. When you replace soil around the plant to firm it in and complete the planting, this should be a blend (layers) of the soil that was originally there and some compost or Garden Mix. The latter can work with the clay to help change the clay soil texture and add a bit of extra nutrient for the plant.

Lastly, apply a layer of mulch even though we’re heading into winter. Why? Among its other characteristics, mulch has large particles which help move rainwater evenly around the soil area, plus it will head off competing weeds while the plant establishes. Never place mulch right up against the stem of the plant though, form a ‘collar’ around it.

Ongoing annual care: Twice yearly applications in spring and summer of compost or Garden Mix, forked around plants are recommended. If left, clay tends to ‘revert’ to its original structure over a year. A layer of mulch every spring helps retain moisture during dry periods and that, in turn, keeps earthworms near the top of the soil, tunnelling through it and improving permeability.

Tough plants that are great in clay: Many New Zealand plants cope well in tough growing conditions. These plants establish with ease, after the first year of care:

  • Trees - lemonwoods and pittosporums, kowhai, ngaio and ake ake
  • Shrubs - coprosma, camellias, corokias, manukas, some olearias, callistemon, westringea (Australian rosemary), viburnum
  • Grasses - carex secta and carex virgata
  • Groundcovers - grevilleas, coprosmas, ivy

Root rot: Plants that suffer root rot (phytophthora) generally get it when planted in poorly drained clay soils. This can often be seen in rhododendrons and the NZ Griselinia. Reduce the risk by limiting the use of the plants to a few. Use Rootmate, which is a natural beneficial fungus in the hole at planting. It will eat the phytophthora which attracts roots.

Dealing with Sandy Soil

Light sandy soils may require little or no preparation but they will need an extra layer of compost or organic matter worked in.

When preparing light sandy soil add a thick layer of compost or organic matter on top, around 200mm, and fork or rotary hoe this in. The organic matter will help improve the soil and improve water retention.

Mulch light soils heavily as this will help the overall structure and improve water retention.

If the light soil is initially very dry you may need to consider using a water penetrant to help get moisture into the soil, as very dry soils can become hydaphopic  i.e. almost waterproof.