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Growing Guidelines

Preparation   |   Planting   |   Container Growing   |   Hardiness Zones 

At Tharfield Nursery Ltd everything is grown in containers to minimise transplant shock and enable planting in your garden all through the year. To accomplish this the guidelines below will enable you to do this successfully.


Firstly to prepare the plant itself for planting soak the whole container in a bucket of water for up to half an hour. After this time there should be no bubbles arising from the potting mix and all the root ball will be fully saturated. This is important because once the plant is in the soil, water will not move from the soil to the root ball unless there is sufficient water in the potting mix to attract the soil particles and build a capillary path to draw it in.

Soil preparation is important to prepare the plant's new home and enable it to settle in successfully. Dig into the planting site as much compost as you can. At least 3 times the volume of the pot worked into a planting site that is twice the diameter of the pot would be a minimum. This will enable the soil to merge with the potting mix successfully at planting time, as well as provide enough nutrients until the plant is fully established and ready to fertilise as part of your normal garden feeding regime.


The best time for planting is autumn, however when dealing with tender species, spring planting is best once all risk of frost is past. This way the plant will establish and build up a good root system to obtain all the nutrients it needs to ripen its growth through the summer. Well ripened growth is more hardy, even on tender species, and thus more likely to handle light frosts.

Dig the hole ready for planting and then de-pot the plant. At this point you must decide how much root disturbance is needed. In summer it is recommended that you only gently break the shoulder of the root ball if it needs it down to one third the depth of the pot maximum. If there are circling roots running right around the bottom of the pot simply cut these at 3 evenly spaced points around the base of the root ball and disturb it no further. This is adequate to avoid future problems as well as all a plant can handle during the hotter months, even with the best of aftercare.

Dormant plants in winter can handle more root disturbance but the above guidelines are usually enough for any plant at any time of year.

Under no circumstances disturb the roots of avocado at planting time. These are grown in specially designed bags or containers to prepare them for minimal transplant shock and disturbance.

Once the plant is in position gently backfill the hole and firm in the soil to the same depth as the potting mix or slightly above. A slight hollow around the plants stem will make sure water will move into the potting mix of the root ball as well as the surrounding soil.
If the plant needs a stake for support this is best positioned before backfilling to prevent root injury.

Water in well. Deeply water regularly to ensure a damp root zone, but one that is not too wet.

It can be anywhere from 1 to 4 weeks before the roots emerge from the original root ball and can sustain the plant from the surrounding soil.

Container Growing

Ever since man has wanted to grow plants he has tried to grow them in containers.

The success of this growing method depends on 4 things:

  • the species
  • the growing medium
  • the container
  • the nutrient requirements

All of these ingredients are interrelated.

Most plants are designed to grow in an unrestricted environment, whether it is in the ground or perched in a tree, as in the case of epiphytic plants such as ferns or orchids.

Recognising the natural habitat of the species concerned gives a good indication as to the right growing medium for the species and also the right container, since the container often will modify the properties of any growing medium.

Always use a commercially designed potting mix to avoid drainage and disease problems associated with soil in the restricted environment of a container. The addition of "water holding crystals" can be beneficial, and always be conscious that the root zone in a container can get very hot depending on placement and colour of the container.

Drainage is the most important aspect of container growing and it is the drainage/aeration properties (the ability to shed water as well as supply air to the root zone) of a medium that are most affected by the choice of container.

Drainage is affected by the particle sizes in the medium and the proportions of each size or structure dictate how readily water will creep upward or move downward due to capillary action. Finer particles allow water to creep further up into a medium against the force of gravity, so that water can literally hang in a growing medium. Water will move downward through a medium in response to gravity from coarse particles to finer particles very easily until it is held in place by capillary action. If it reaches a barrier such as the bottom of the pot or some of the old fashioned "crocks", then the layer of water that will be suspended in that particular medium will sit there. The old fashioned "crock" idea actually impedes drainage as do pots that do not sit flat on the ground since this breaks the capillary column. Polythene growing bags actually provide the best capillary contact with the ground, and therefore the best capillary or drainage column, as long as it is sitting on sand or another medium with similar capillary properties to the growing medium. If the planter bag is sitting on coarse gravel the capillary column is broken and a layer of water will hang in the bottom of the bag.

Shallow trays such as traditional Bonsai trays therefore can become quite wet if the growing medium is quite fine. Since all growing mediums break down with time and as this happens the drainage and aeration get worse, it is best to repot each spring and replace at least 1/3 of the volume of the medium with fresh material.

Feeding container plants

The ideal nutrient supply comes from slow release coated fertilisers which release nutrients in response to medium temperatures and moisture content. When using these products be sure to take note of the longevity and actual nutrient content of the product, since these factors will indicate when and what supplementary feeding is required.


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