Watering
The first thing to remember is that olive trees really (and I mean REALLY) hate having wet feet, so make sure that if you have planted yours in a pot, there is plenty of drainage. If it is in the ground, make sure it's planted in free-draining soil and not in a waterlogged or boggy area.
After all I have just said, I realise what I'm now going to say may seem bizarre... but... it is true that I regularly find one of the biggest mistakes people make is assuming that, because olive trees are drought tolerant, they don't need watering... at all.
I get it. It's an easy assumption to make when you see them growing happily away in the Med where it's a million and one degrees, looking like some of the happiest plants on the planet (they probably are, too). But if they've not had any water for a few weeks, even in mid-winter, they are probably really rather thirsty!
What is easy to forget is that those wild trees have enormous root systems stretching away beneath that dusty, hard-baked ground, giving them an incredible life support system.
When the olives you buy from us (or, for that matter, any other nursery or garden centre) are lifted from the ground and shoved into pots, the root system is massively reduced, which in turn heavily reduces that plant's life support. The tree now ultimately relies on what you give it, both in terms of food and water, at least until it is established in the ground. It will rely on you for the rest of its life if you keep it in a pot.
There is, unfortunately, no precise amount of water I can tell you to give because we have this wonderfully variable thing called The British Weather...
Through the winter, watering isn't always necessary as Mother Nature tends to give us a fair whack of the wet stuff. Spring, summer and autumn (so, most of the year) are when you need to keep a closer eye on watering.
During a dry spell (more than a week or so), we would be putting around 7–10 litres a day onto an olive with a root ball (pot size) of around 60–80cm in diameter, whereas a pot measuring 30–40cm would likely need around 4–5 litres. Bigger will need more, smaller will need less...
This amount can be reduced to every few days when it's cooler, and then again to once or twice a week when the weather turns cold.
Be careful watering during winter when it is actually freezing. I don't recommend watering when they are frozen solid. Instead, wait for them to thaw and then check how wet the soil actually is.
If there is an odd rain shower, I wouldn't assume that's enough; just keep checking at regular intervals. With showers, it is unlikely the water will have permeated much beyond the first half inch of soil, so your olive will probably still need watering if we are lucky enough for the weather to be on the warmer side.
Feeding
Feed with a good handful of Vitax Q4 in March or April and then again in mid to late August or September.
Trimming and Pruning
A light trim can be done all year round, so long as you are leaving plenty of foliage on the plant.
If you are giving it a hard prune (which is perfectly alright — when olives are taken out of olive production and moved into the ornamental market, their tops are quite literally chopped off down to a stump from which they mostly regrow), it is going to leave your tree looking pretty bare for a while, or even completely bare, which is pretty scary. But it will come back!
I would recommend doing any hard pruning in early March at the same time as you feed it. If the weather is still particularly cold in March, just hold off until April.
You really can prune them as hard as you like — they will grow back! Don't panic if it takes a while for new shoots to appear. It can take six weeks or more for the plant to get going again.
Once you get the feel of looking after your Olea (Olive), it will become second nature. Just remember, they don't like being too wet... or too dry... and you'll have a happy olive!
