Plant pot advice

Without doubt, the biggest killer of patio plants, house plants and any other potted plant is ‘death by rotting’. It’s a slow agonising death for any plant, it’s also unsightly and expensive for the gardener. So it makes good sense to avoid it if at all possible. On this page I’ll explain why your plants are dying and how to prevent most of your losses – simply. The range of flower pots today is staggering. There are large garden pots, terracotta pots and planters of all shapes and sizes.

Gardener’s have been told to put broken crocks or stones in the bottom of their pots ever since man began to garden in containers. Trouble is, the advice was given when gardeners were using terra cotta pots and the crocks were pieces of broken pot. Only now, in the 21st century we are using plastic pots and bigger pots and losing plants to avoidable rotting more than ever. So isn’t it time therefore, we had something of a rethink about our garden pots and garden potting?

The plastic pot is king and for good reason. It’s easily and cheaply mass-produced, has great ‘stackability’ and it’s lighter to carry than any other plant container. It has a great many things going for it.

But unlike terracotta pots, plastic pots don’t breathe.

Plastic pots have two distinct disadvantages.

1. Plastic flower pots ‘sweat’ inside.
2. Many flower pots, especially the larger ones, simply do not have enough drainage holes.

Leave a plastic pot outside and the winter sun will warm the contents during the day and the cooler night air will create condensation inside the pot. No problem for a week or two, even with most plants. But the constant wet-dry in a covered environment with minimal airflow for months on end will weaken your plant. And if its roots are cold and wet it will succumb. But, with borderline tender plants or exotics of any kind and this daily sweating can become a killer very easily.

Unless additional precautions are taken.

Good drainage is essential – check plant pot holes

When choosing a plastic flower pot or planter you need to consider the number and size of the drainage holes your particular plant requires. How many? A flower pot can’t have too many. Check out the picture below:

Pictured on the left are a 2 litre flower pot and a 30 litre patio pot. The 2 litre example has not only more drainage holes, but four of them are larger!
The two litre pot is an excellent pot. But if the 30 litre pot is used just as it is, which is not uncommon, the gardener will almost certainly a larger, valuable plant before the end of its first winter.

In my own experience the problem is even worse with 65 and 90 litre garden pots. The 120 litre pots I used arrived with just three holes!!

The solution for this particular problem is very easy. Use a 25mm carpenter’s hole borer to increase the number and size of the holes.

The larger the pot the easier it is to kill it with kindness!

When plant pot sizes head towards the 30 litre mark and above the gardener needs to be more creative as these larger pots create their own problems in addition to the obvious ones of handling and weight for the ‘larger planter’.

Killing your plant with kindness? The larger the pot, the more you are likely to kill your beloved plant with kindness!

Fact: If a plant is dying of thirst its leaves will droop. If a plant is drowning its leaves will also droop.

Gardeners must be aware of this very common contradiction. When the gardener comprehends it, the demise of so many house plants and pot plants can be more readily comprehended.

Imagine for a moment that your prized pot plant is actually ‘drowning’, but you look at its drooping leaves and decide that it’s dying of thirst. So you add water, probably quite a bit, especially if the air is warm and dry. Only giving additional water to a drowning plant will only hasten its death.

In a large pot the surface soil will become like dust in just a few days as the moisture seeps downward under gravity. But, if there are insufficiently numerous and large enough drainage holes in the pot, the plant root is effectively in a bog. Even though the topsoil looks like dust.

If your pot plant with droopy leaves is under say 20 litres capacity, the answer is easy. Just pick it up. The wet plant will be heavier.

For larger plant pots its not nearly so easy. So I tended to err on the side of dry if there was any doubt, and I suggest you do the same. if for no other reason, than more plants have died from being too wet, than too dry!

More care is needed when potting up the larger pot plants

It is not enough to simply drill more and larger holes in the bottom of your large planter or pot – though it will surely help – it won’t be enough.

Because large pots need filling differently.

1. The total compost required to fill a large pot or planter needs to be roughly divided in to three for each third of the pot.
2. In the lowest third, the compost should consist of 2/3 coarse drainage material or grit. Perlite is excellent, because it’s both inert and lighter.
3. The middle third of the pot should be filled with a 60/40 mix of coarse grite or perlite and compost.
4. The uppermost third of the pot should be filled with 100% compost.

I’ve used this basic mixture for over ten years with remarkable success. Of coarse this recommendation is not ‘carved in stone’, but taken as a useful guide line. For example, as it is, it works great with Cannas, hedychiums and hibiscus. But bougainvillea are happier with a the middle portion around 50/50 and the top third with 25% perlite added. It pays to experiment. But I’m certain, the basic recipe will save many ‘specimen plants’ that would otherwise succumb.

A word of warning about some styles of terracotta pot before you buy

There are a great many beautiful terra cotta pot designs. But do beware of the fact that when it comes time to re-pot that plant in its terracotta pot, you can’t thump the base with a spade! Nor can you drop the pot on the ground to loosen its root ball from the pot sides.

And don’t forget those beautiful terracotta pots shaped like an urn or vase – those with narrow necks. Not only are they difficult to fill, they’re difficult to water and it’s  near-impossible to move the plant without breaking the pot!