DO’S AND DON’TS OF CONTAINER GARDENING
BASIC INSTRUCTIONS FOR SUCCESS WITH POTTED PLANTS
THE following is a reprise of my July 2016 article due to popular demand.
One of the unfortunate consequences of modern urban development, particularly for gardeners, is the gradual loss of spaces where gardens can be actually established in natural soil, due to shrinking blocks, expanding homes, larger entertainment areas and concreted driveways for two or more cars.
In addition, many city dwellers are now opting for unit and townhouse life, sometimes resulting in having no outdoor space except for maybe a balcony or deck.
For those who can’t live without their plants (and let’s face it, who can’t?), the only option for gardening in these spaces is to grow them in containers.
To many gardeners, growing plants in containers can be both rewarding, and frustrating!
There are many reasons why we might choose to pot up a plant.
Some, for example, being epiphytic growers, including various orchids, ferns and bromeliads, simply don’t grow in soil, so pot culture is the only option.
Others, such as some Western Australian native plants, may require a sharp, sandy, well drained potting media in which to thrive, easily supplied in a container.
And don’t forget that hard-to-grow, rare and exotic variety that might need a special growing position, best provided in an easily-moved pot.
Now let’s consider those gardeners who are not usually rewarded, but generally frustrated, by their attempts at growing containerised plants, and the reasons why they may not be successful.
This may seem painfully obvious, but the main cause of pot culture disasters is poor plant choice.
Don’t impulse buy, do your research, or ask a qualified horticulturist before making your purchase.
Please remember that nothing beats old-fashioned local knowledge, so consult your nearest nursery person before searching the internet.
Next on the list will be your choice of container. In most cases, the container you choose should be at least the same size as the pot in which the plant is purchased, or the next size up.
The vigour of the plant will affect this decision, with a slow-growing plant, for example a dwarf conifer, not needing a much larger container for a year or two, but a petunia, maturing from a punnet seedling to full size in maybe 12 weeks, requiring a fair amount of spare volume for a rapidly growing and voracious root system.
Next in line for consideration will be your potting media.
It’s best not to use garden soil in pots, as it can be the source of unwelcome pests, diseases and weeds, as well as causing root-hindering compaction.
A premium mix (red ticks) formulated for the type of plant you’re growing is best, as it should be manufactured to their physical (aeration, water-holding) and chemical (pH and nutrient) requirements.
If you’re confident, then purchasing a general Australian Standard mix (black ticks), and incorporating the necessary additives for your plant variety, may be the way to go.
Some specialist plant clubs may have their own successful recipes for potting mixes, and there are many great books written by authoritative gardening figures in which potting media mixtures are listed.
Once potted, you will need to decide where to site your plant.
This is where knowledge of micro-climates can be an advantage for containerised growing, with the gardener able to move their plants to favourable positions as dictated by seasons or weather conditions.
It’s recommended that all pots be raised above ground level (using pot feet or bricks), particularly above soil or gravel paths, to prevent the incursion, through the drainage holes, of possibly destructive pests such as nematodes and curl grubs, and the splashing of soil-borne nasties such as fungal spores into the pot.
When it comes to providing sufficient nutrients to containerised plants, nothing comes close to a quality controlled-release fertiliser, either incorporated into the mix when potting, or as a top-dress on established plants.
Once applied, they commence releasing their nutrients (usually both macro and trace elements) pretty consistently over the time period specified (from 3-4 months for our previously mentioned Petunia, to 12-14 months for our conifer).
Soluble fertilisers come second to controlled release for effectiveness, but there’s much more time and labour involved in mixing and applying, sometimes as often as every fortnight.
Many organic fertilisers just don’t work well in potting mixes.
Providing sufficient moisture is always a challenge for those growing potted plants.
The quality of the potting mix has a great effect on this, with the peat-based mixes the best for water holding capacity.
Look for mixes that have water-holding materials as added components.
Resist the temptation to add water crystals, as too many can actually push the potting mix out of the container!
Avoid long-term use of pot saucers to hold moisture, as these can lead to a constantly wet potting mix which breaks down, turning sour and killing plant roots.
If a mix dries out fully, re-wet by submerging in a bucket of water for about ½ hr, then sprinkling soil wetting granules (not too many!) on the surface of the mix after removing and draining.
For containers positioned out in the open, use a decorative mulch, such as pebbles, as this will reduce evaporation considerably.
Best of luck with your containerised plants!