You don’t need to own an acreage to grow large shrubs and fruit trees –a balcony, veranda, patio or along a driveway are all good places for growing plants in pots. Perhaps you have large trees in the garden, and root competition precludes growing in the ground. Perhaps you want to green a paved area, or perhaps – as in my old garden – the only sunny places are alongside the northern wall of the house on the concrete, and everywhere else is just too shady.
When we moved into our house nearly thirty years ago, my in-laws gave us several large potted camellias that they ad been growing under their pergola in Whyalla. Some I planted into the ground, but two went into even larger terracotta pots, where they are still happy and thriving after nearly three decades.
Out the front of the house, Camellia ‘Guilio Nuccio’ was transplanted from my Oma’s garden after my Opa died about fifteen years ago; the central camellia is a seedling from under another potted camellia, while the Japanese maple on the left was a ten centimetre seedling dug from gravel at a nursery where I worked twenty-five years ago.
Because of their links to friends and family, many of these plants have great sentimental value, and most of them now reach the eaves and are a couple metres wide – large enough to be significant structural elements within the garden.
I’m also currently hosting a lemon and a lime tree (right) that I gave to my two daughters after they left home but before they became nomadic –one day they may be reunited!
So how have I kept all these plants healthy and thriving for decades? Read on!
1. How to select the right plant pot or container
For citrus, camellias, dwarf fruit trees and most Japanese maples, choose a pot about half-wine barrel size, slightly smaller for dwarf citrus. However, it’s a bad idea to plant tiny specimens (especially citrus) into huge containers – the mix stays waterlogged & promotes disease. Instead, pot into an intermediate-size cheap plastic tub, placed inside your good container if you want a nicer aesthetic.
Raise the inner pot with chocks for drainage, and mulch with straw to hide the plastic pot. Keep mulch away from trunk. I like to seal terracotta with Pot Seal to reduce watering. Of course, you can break all the rules with tough plants and still succeed, like this 20cm fig in a pot that’s considerably larger than a half wine barrel. It looks ridiculous right now (spot the fig!), but figs are hardy and fast-growing, and I was feeling lazy.
I’m no fan of half wine barrels – in my opinion, they require automatic watering systems or complete dedication because, if barrels dry out even once, gaps appear, watering becomes impossible, and the barrels fall apart. Light-weight fibreglass & plastic faux terracotta pots are fantastic if you need to move them around.
Unless your plant will definitely remain in its current container, choose pots with rims wider than the body – getting a large rootball out of a narrow-rimmed pot is a nightmare. Ensure your pot has plentiful drainage holes &/or large ones.
Use pot feet for drainage, especially if your pot is sitting on soil rather than paving or cement. If you don’t raise the pot, the roots are likely to grow through the holes and eventually block them, waterlogging the pot and killing the plant.
The other outcome is a small pot clinging to the trunk of an established tree, with the root system in the ground beneath, like my two-metre high Nagami cumquat in its 45cm pot!
2. How to choose the right growing medium (potting mix or compost)
Quality potting mix only (yep, I know this is the topic of a whole ‘nother blog but, basically, you get what you pay for). NEVER add garden soil unless you know exactly what you’re doing, because to miscalculate the proportions and/or texture is to create clogged drainage holes or a water-repellent, un-wettable shrinking mess. Ask nursery staff whether other additives are suitable for your tree and container.
3. How to choose the right location for your potted plant
Depends on where you live, of course. Here in the Adelaide Hills, it’s full sun for most citrus & fruit trees like my Shahtoot mulberry, and morning sun /dappled shade for camellias, maples, blueberries etc.
North-facing walls are ideal for warmth-loving citrus, but watch for the drying effect of eaves & verandas in winter if you’re relying on the rainfall and not watering. In hotter areas with dry summers, plants may do better on the northeastern/eastern side of houses where they get protection from the afternoon sun in summer.
In our cool Hills climate, I pot citrus (and subtropical fruit trees) any time except late autumn & winter. I avoid potting any trees during very hot windy weather and I allow at least 7-8 cm between potting mix surface & pot lip for mulching & watering. Potting mix will settle after watering so allow for this.
Once the plants are established, shallow-rooted perennials and annuals often seed and naturalise underneath, like the lettuce under the ginkgo, or the mouse plant under the maple, and they seem to cohabit happily. However, I remove vigorous and deep rooted perennials, like parsley and aquilegia.
5. When and how to fertilise your potted plants
I feed evergreen fruit trees in spring, summer & early autumn with a slow-release balanced organic pelletised fertiliser (eg Sudden Impact, Gyganic) and/or Osmocote for Fruit & Citrus, or alternate the fertiliser types depending on what’s in the shed! However, I don’t apply general purpose concentrated fertilisers designed for general garden use because I discovered from bitter experience that it’s very easy to overdose potted plants, burn roots, and to create salt build-up over time. All pots get a Seasol tonic in winter and again in early summer.
Citrus (except for Makrut lime) are incredibly greedy – I didn’t have real success with them until I actually began fertilising at recommended rates, which for the huge pots was about a small round plastic takeaway container of slow-release fertiliser, much more than the small handful I had been giving them! l feed deciduous plants like my maple and persimmon in August and November.
6. When and how to water your potted plants
Here it’s every 4-7 days throughout growing season, more often during heat waves or warm windy weather. To reduce salt build-up, I water until it just begins to flow from drainage holes. Over-watering is more likely to kill your plant than under-watering so, if you’re not sure, check soil below surface – if it’s moist 1cm down, no need to water yet. Use pot saucers during heat waves when daily water may be required, but avoid continually water-filled saucers, especially in winter and for citrus. I ensure any pot saucers are very small, so there’s no huge reservoir of water.
If you have many large pots, an automatic watering system will transform your life. Seriously. No more begging family or friends to water pots while you’re away, only to return and realise they’ve forgotten one. If you have to pay someone to come and water your pots, a simple automatic system will pay for itself in three weeks in summer. You can use coiled Miniscape or, as I have, several shrubblers per pot. Mulch pot to minimise evaporation, but keep the mulch away from the trunk. Soil conditioners and wetting agents (especially non-detergent ones like Eco-hydrate) are useful to re-wet potting mix.
7. When and how to renew the potting mix for your potted plant
After 5 -10 years, if roots are crowded (you’ll know because the mix becomes hard, and hard to wet), you can lift the tree from its pot, slice off the bottom 10-20cm, add replacement mix to pot, & return the tree to its container. If it’s too big to lift, you can cut two or three evenly spaced cake-slice wedges out of the mix & replace them with fresh mix. Mark inside pot rim at locations with crayon. Repeat next 3 years in different sectors. I’ve never needed to do this with citrus or camellias, but I’m experimenting with dwarf Corymbia and their more vigorous root systems will probably need pruning.
8. How to prevent lop-sided growth on your potted plants
Plants that are shaded on one side to prevent lopsided growth. This camellia had grown bare on the shaded side, so I turned the bare side sunward. In a year or two it will even out.
9. How to tackle potted plant problems
You need to do something at the first sign of plant stress. Usually, it’s too much or too little water or fertiliser, which can be remedied if done early – take photos (include the location in the shot, as well as a few close-ups of leaves) and bring your camera or mobile to your nearest nursery, where you’re more likely to receive good advice from knowledgeable horticulturists than at the large general hardware/garden centres.