WHY GROW IN CONTAINERS?

No matter what plants you wish to grow there is sure to be a container in the right size or material to suit your needs. Plant containers are available in a huge variety of shapes, colours and textures that really add to the appearance of your garden.

  • To improve drainage.
  • As a feature - the container can provide an eye-catching display, or talking point in it's own right.
  • To restrict the spread of invasive plants (eg: bamboo)
  • To separate plants from other more vigorous plants that might out-compete them.
  • To provide a contrast in terms of colour, texture and shapes to your plants. For example, the rounded contours of may containers will contrast with the irregular shapes of most plants.
  • To alter the height of plants in the garden. This allows for greater variation, plants can be raised to a better viewing height, and they can be used to give height for creeping/hanging plants.
  • To allow the use of tender plants. These can be removed to protected places when growing conditions are poor (eg: during winter, or the peak of summer).
  • Plants in can be moved into a prominent position while flowering or foliage is at an attractive stage), and then moved to a less prominent when out of season. Likewise deciduous plants can be moved deciduous plants.

 

CHOOSING A CONTAINER

Just about any container can be used for growing plants provided it contains sufficient soil or potting mix for the plant to grow in, it has suitable drainage, and does not contain or release any contaminants that may be harmful to plant growth. To get the best results, however, consider the following factors when choosing a container:

 

  • Wider containers are more stable (less likely to tip over).
  • Make sure the container has sufficient drainage holes to allow excess water to drain away quickly. Be careful also that the drainage holes are not to large making it easy for potting mixes/soils to fall or wash out of the container easily.
  • Choose the right size of container for the type of plant you wish to grow. A plant that will not grow very large will look out of place by itself in a large container, while a vigorous grower will soon outgrow a small container. In this case it is important to either re-pot regularly or choose larger containers to allow for such growth.
  • In deeper pots the weight of the potting mix/soil will compress the potting mix/soil beneath reducing air spaces in the mix. A more open mix should therefore be used for deeper pots.
  • Plant roots tend to coil more in round pots than they do in square ones. Root coiling is also reduced if the base is more tapered.

WHAT SHOULD A POT BE MADE OF?

 

Plastics

  • Lightweight
  • Available in a large variety of shapes, colours and sizes.
  • Doesn't dry out as fast as wood or terracotta.
  • Some types of plastic deteriorate in ultra violet light, and crack after just a couple of years. Some of the more expensive types have UV inhibitors than give them much longer lifespans.
  • Cost varies considerably - some are very cheap, some of the heavier, more decorative types can be reasonably expensive, although still generally cheaper than most other materials.

 

Terracotta

  • Available mainly in 'earthy ' colours, such as browns and orange-browns.
  • Unglazed terracotta absorbs water from the potting mix. As a result such pots need to watered more regularly than those made of non-absorbent materials. Plants which prefer a drier, or well drained soil will often prefer a terracotta pot.
  • If the pots are too wet they can often show unsightly white salt marks or grow algae on the sides.
  • Heavier than plastic, making the containers harder to move, but also less likely to blow over.
  • The major disadvantage of terracotta is that they can easily damaged if knocked (a bit brittle).

 

Glazed Ceramics

  • Similar characteristics to unglazed terracotta, except that glazing makes a water impermeable layer, which reduces the rate at which the pot dries out.
  • The glazing also allows for a greater range of colours, and decorations than for unglazed terracotta.

 

Wood

  • Timber can look great, but can easily rot if not treated. Be careful that the preservative treatment used is not toxic to plants.
  • Timber can be used rough cut, it can be finished, it can be stained to provide different textures and colours.
  • Timber will withstand more knocking than will terracotta.
  • Timber is generally light to moderately heavy depending on the type of timber used.
  • Timber has the advantage that it can be readily cut and joined to produce non-standard shapes or sizes.
  • Wooden wine casks make a very attractive container for larger shrubs and small trees.

 

Concrete

  • Reasonably expensive
  • Available in a wide variety of shapes and sizes.
  • Generally strong, and not as brittle as terracotta.
  • Quite heavy.
  • Will not rot
  • Some available in coloured concrete, but generally bought uncoloured and painted as required.
  • Most widely used for larger plants as the concretes heavy weight provides stability.

Brass

  • Limited colour range
  • Expensive
  • Very durable
  • Most widely used for indoor plants
  • Usually treated with a solution to keep it from tarnishing.
  • Relatively heavy in larger sizes.
  • Can dent if knocked heavily
  • Long lasting/durable.

 

Water Well Pots

These are pots having an extra container or well beneath the main container that holds a reserve of water that can supply the plant for extended periods of several, or even more, weeks. The water is drawn up from the well by capillary action. The well is refilled through a hollow tube that reaches from the surface of the upper pot down into the well.

In some types clear plastic is used for the well section. This can sometimes lead to algal growth problems in the well; and pests eg. mosquitoes) can breed inside the well. Most commonly made of plastic this type of pot is commonly used for growing indoor plants.

 

CARING FOR PLANTS IN CONTAINERS

  • Soils in containers usually dry more rapidly than those in the ground because the container is more exposed to the elements (eg: wind, sun). This means that greater care must be taken when watering plants in containers than for those in the ground. Simple drip irrigation systems with individual drippers to each pot are a good way to overcome this problem.
  • For plants that are to be grown in open sunny positions avoid dark coloured pots that will absorb a lot of heat from sunlight. This can generate high temperatures in the soil that can severely damage plant roots. Light coloured, glazed pots are good in such a situation as they will reflect a lot of the sunlight.
  • Roots tend to grow through the bottom of containers when they are placed on top of moist soil, compost or moist organic mulches. This can make them difficult to move and re-pot. Containers are best placed on top of a dry paved surface where roots protruding from the drainage holes get naturally root pruned by the dry exterior environment.
  • Sprinkling a layer of coarse sand over the soil surface in a container will reduce weed problems and control the growth of moss.
  • For larger containers mulches can be added to the soil surface to reduce water loss, to act as a buffer against
  • When going away (ie: on holiday) you may need to move your container grown plants into a protected position out of direct sunlight and away from winds. An automatic irrigation system, on some sort of timer can also be used. In the warm months you might also place your containers in a trough, bath, or similar container holding water, taking care not to immerse more than the bottom one-third of the container.

 

POTTING UP

How often you re-pot will vary considerably depending on the type of plant you are growing, the conditions they are growing in, and the type of container they are growing in. Some plants, for example Hoyas and Cymbidiums, seem to flower best when they are somewhat root bound. Most plants, however, do their best when they are regularly re-potted into larger containers, with fresh potting mix.

  • when to re-pot (season, when pot bound, etc.)
  • how to re-pot ( pruning back root bound sections - or teasing out, etc)

INDOOR PLANTS

Growing plants in containers is the most the most common way of using plants indoors.

There are four major factors that need to be considered when growing plants indoors: These are:

* Temperature - sudden changes usually biggest problem heaters/air conditioners going on and off, doors opening and closing, cooking appliances in kitchen

* Light - can be to bright (eg near a window), or to dull. Lights being turned on and off, or being used for extensive periods can affect plants physiological response (photoperiodism). Dust on leaves can block up leaf pores (stomata), also reduce the amount of light reaching the leaf itself.

* Moisture - low humidity/dry air (particularly when heaters are being used). No natural rainfall to keep foliage moist (or to wash of dust)

* Gases/ventilation

 

 

POTS THAT AREN'T REALLY POTS (use your imagination)

 

Tyre Gardens

Old tyres can be readily stacked on top of each other, or just a single one layed on the ground, and then filled with soil or potting mix to provide a container or bed for growing plants. The tyres provide a soft, durable material that will not damage mowers or other machinery (or children!) if they bump into it. The tyres can stacked in columns, one on top of each other, to provide a deep container, or they can be stacked offset from each other, or tyres of different sizes used, to create planting pockets. The tyres can be readily painted to a suitable colour, and if desired holes can be cut in the tyre wall to provide extra planting spots.

 

Old wheel barrows

These can be painted with a preservative to prevent them rusting out, and then filled with a suitable soil or potting mix and planted out. Make sure to provide for sufficient drainage, and be careful the metal trayed wheelbarrows don't get to hot in warm weather.

 

Old concrete troughs or baths

These are an easy way to make a simple container for water or bog plants. The old drain plug should be securely blocked to prevent leakages. Make sure the trough or bath is stabilised to prevent it rocking if anyone sits on it's edge. If the container is large enough you might even be able to keep some fish in it. These will help keep down mosquitoes that may breed in the still water.

 

Hollowed out logs/stumps

These can be used in their original position (ie: where they have fallen or grown), or can be placed into a suitable position. Natural or created hollows can be filled with a suitable growing media, preferably a highly organic, well drained mix, and planted out with things such as ferns or cymbidium orchids. Drainage holes may need to be drilled near the base of hollows to ensure plants don't get waterlogged. This type of 'container' would look great under tree cover in a natural or bush garden.

 

*Hollow bricks

Hollow building bricks (eg: besser) can be used to make an edge to a garden bed, pathway or driveway, or can be stacked to create a raised bed or retaining wall. Hollows in the side of the bricks can be filled with soil and planted out (eg: trailers, rockery plants, annuals).

 

*Pipes

Large diameter concrete or terracotta pipes can be stood on end and filled with soil/potting mix and planted out to alter the profile of a garden. They can also have their ends plugged with a water proof material (ie: concrete to create a suitable container for bog or water plants. the pipes can be left sitting on a paved surface or they can be partially buried in the ground to provide stability.

 

 

 

 

BONSAI

 

Bonsai is the art of training young seedlings or cutting grown plants, or the sculpting of established plants to represent miniature trees. These living, artistic, container grown trees are an ideal way to have a garden in miniature, and they will create much interest amongst your family and guests.

 

Bonsai growing is a leisure pastime that places humans as one with nature. Elements of nature, such as wind, lightning, snow, the blazing sun, seasonal changes, in fact most of natures many faces can be shown or implied in miniature by the use of imagination and basic gardening skills. Wind might be implied by way of creating a leaning trunk or branches growing horizontally in one direction. Light can be suggested by carefully peeling away the bark at the highest points of upright trees to imply that these tips have been struck during a storm. A lake or the sea can be implied by artistically placing small pebbles and sand on the soil surface near the rim of the bonsai container creating a miniature beach suggesting water.

 

The basic techniques involved in the training of bonsai trees are feeding, pruning, wiring, bud pinching, and careful watering.

 

Root Pruning and Potting-Up Bonsai

The primary function of pruning the roots of a bonsai tree is to ensure the health of the tree. Since the roots of the tree are restrained by it's container they tend to wind round and round the inner surface of the container, which compacts the soil, thereby depriving the plant of air and water. If these long roots are 'teased' away and removed with sharp trimming shears then air and water can circulate freely through the soil/potting mix.

Root pruning and re-potting of bonsai is generally carried out from late autumn to early spring. Some form of protection from extreme cold should be provided if it is done in winter.

 

When potting up use some shadecloth or fly wire to cover the drainage holes in the container. A coarse component of your potting mix, or some small pebbles should cover the shadecloth or fly wire to help provide good drainage. Potting mix can then be applied to cover the pebbles.

 

The tree to be planted should have any dead roots removed, and some of the healthy roots should be teased out from the root ball. The tree can then be positioned as desired in the container. Fresh potting mix can now be filled into the pot, and using a chopstick or similar implement can be lightly compacted around the rootball. Water the pot thoroughly, then plant moss on top of the potting soil. If the tree is top heavy you made need to wire it in position until it has established.

 

Bonsai Pots/Containers

Bonsai can be grown in a wide variety of containers, but are most commonly grown in small shallow dish or bowl shaped containers. Ceramic, glazed or unglazed, is the most widely used material. Pots made specifically for bonsai are readily obtained from bonsai, and some of the larger general nurseries.

 

Potting Mixes For Bonsai

Drainage, water retention, aeration, and nutrition levels are all important factors in choosing a potting mix for your bonsai. To ensure good drainage, yet still retain sufficient moisture for healthy plant growth try a mixture of mulch consisting of well rotted compost or animal manure, or fine pine bark, in equal parts with clay grit. The clay is best collected in a dry state as the granular structure of the clay is preserved. The fine powder and larger lumps are sieved and discarded, then the remaining granules mixed with the mulch. If the clay does not contain a reasonable gravel or grit component, this can be added separately. At this stage fertilizers, and trace elements can be added. Mixes containing coarse pine bark, or high percentages of sandy soils should be avoided as they generally give poor results.

 

Wiring Bonsai

Bonsai trees are wired to control the direction of growth of a branch, twig or trunk. The most common use is to direct upward growing branches downwards to give the impression of great age. Copper or aluminium wire with greater bending resistance than the desired branch is normally 'anchored' around the trunk then neatly wound to the end of the branch.

Wiring is best done when the tree is in a semi-dry condition as the woody parts are flexible to bend without causing major damage. The wire should not be wound tightly around branches as this can cause damage. Bending of branches should be done very carefully. For thicker branches it is best to bend the branch in the desired direction as you wire it. Wires should be removed before branches thicken. For young vigorous trees wires should only be left in position for a few months. For older established trees it can sometimes be left for several years. Wires can also be used to pull branches down by anchoring one end of the wire to the container.

 

Top Pruning

For the development of a medium or large bonsai tree a young tree may be allowed to grow vigorously then cut back hard annually for several years to develop a strong trunk and basic shape. Then a more regular trimming program can be undertaken to develop twiggy branches. Most deciduous and hardwood varieties can be cut back to old wood and still shoot new growth, however care must be taken when top pruning conifers as many will not shoot from old wood. The most effective way to prune conifers is to pinch out the tips of new growth. This technique is also used for broad-leaved plants such as azaleas, maples, elms, oaks and beech. As soon as the new shoots have opened out to two or three leaves repeat the process. A sharp pair of trimmers should be used to make a clean cut. Do not use fingernails.

 

Feeding Bonsai

Proper nourishment is essential for healthy growth of bonsai trees. Plants are generally fed from early Spring through Autumn. A five to sixth month slow release fertiliser such as Osmocote provides a convenient single application method. If this method is used be sure to lightly bury the fertilizer pellets below the soil surface, or under moss, so they can't be seen and to help fertilizer retention. Liquid fertilizers, such as fish emulsion can be applied every few weeks.

 

Watering

How often you water will depend on a variety of factors, including weather conditions, the season of the year, the type of plant being grown, the type of container used, and the moisture holding ability of the soil/potting mix. Experience is the best guide to when you should water. Don't be misguided by a lush covering of moss on the surface of the container. Mosses can stay green for long after the pot has dried out. The plants can be easily watered from above with a fine rose watering can or hose. For bonsai that are planted with the soil level with or mounded above the top of the container repeated sprinkling of the container is required. An alternative means of watering is to submerge the container in another container filled with water, being careful not to dislodge the soil/potting mix. When air bubbles cease rising then the plant should be thoroughly watered.

 

Some Plants To Bonsai

The list of plants for bonsai is almost endless, and includes many Australian natives. The following list covers some of the more commonly used ones:

  • Acer (Maples)
  • Azaleas
  • Conifers (most are excellent)
  • Cotoneaster
  • Fagus (Beeches)
  • Ficus (Figs)
  • Fraxinus (Ashes)
  • Leptospermum (Tea-trees)
  • Melaleuca (Paperbarks)
  • Pyracantha (Firethorns)
  • Quercus (Oaks)

 

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