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Canberra Today 15°/18° | Thursday, March 28, 2024 | Digital Edition | Crossword & Sudoku

Gardening: Going to pot or what?

POT culture can be a neglected aspect of gardening, leaving some plants in pots for years, like a lifetime in jail, possibly with roots growing into the ground.

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Using polystyrene as a pot filler.
To prevent this, never place pots directly on soil in a garden bed, rather place pots on a paver.

When re-potting, just getting the plant out of the pot can be a challenge, particularly if it is an Ali Baba-style, tapered pot, a type I never recommend for plants. Depending on the value of the plant, the pot may have to be sacrificed.

Starting with potting up a new plant, here are a few new ideas: usually, the size of the pot is too large for the plant and its root ball and leads to using more potting mix than is necessary. Potting mixes vary in quality and while it is tempting to buy the cheapest, this is a false economy. Spending, say, $50 or more for a beautiful specimen plant and planting it in $5 potting mix is something like driving a Mercedes and running it on standard petrol!

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Pruning roots with a sharp knife.
The roots of most plants will not extend to the bottom of the pot. Very few plants have a tap root. So what is the solution? Firstly, make sure there are sufficient holes in the bottom of the pot or indeed any holes – many imported ceramic pots don’t have drainage holes, which is great for a mini fishpond but a quick death for plants.

Firstly, place a few pieces of broken tile or terracotta over the holes. Next shred some polystyrene to fill the container to a quarter or a third, depending on the variety of plant. For example, azaleas and daphne have shallow roots. With annuals, at least half the container can be filled with polystyrene, reducing the amount of potting mix.

With any plant, it depends on how long it has been in the pot at the garden centre. Check if it appears root bound. This is rarely a problem with perennials as the roots can be gently teased out. Certainly this is never a problem with veggie, herbs or flower seedlings. Incidentally, garden centres report herbs are outselling flowering annuals by a factor of three to one. If the plant is a shrub and has a mass of roots one can be quite ruthless using a sharp knife. Gently cut through the roots in three places from top of the plant to the bottom. Then similarly cut a cross across the base of the plants. The roots will then spread out from the cuts into the potting mix.

Firm the potting mix, leaving a space of about five centimetres from the top for watering. I suggest you plant carpet thyme or similar on the top of the pot as a living mulch, keeping the root zone cool in summer.

Finally, water the plant several times, adding Maxicrop Seaweed Plant Nutrient to promote root growth. All of the above advice can equally apply when re-potting older plants while at the same time trying to reduce the roots and soil by one third for fresh potting mix.

Always raise pots off the ground, even when placed on paving or concrete. Pots do not need a saucer as this leads to bad drainage and root rot and possible death of the plant.

Stuff to do

  • If you have used a pot as a mini fishpond, clean accumulated leaves and other debris from the bottom.
  • Group a variety of pot sizes together to form an interesting display of colour.
  • To prevent terracotta pots drying out, paint the inside with a bituminous paint such as Ormonoid available from DIY stores.
  • Grow a variety of plants in a pot with flowering times throughout the growing season.
  • Focus outdoor lights on a group of pots.

 

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Cedric Bryant

Cedric Bryant

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