Helen McKerralHow to grow plants in large pots long term

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.

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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.

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Camellia 'Guilio Nuccio'

Camellia ‘Guilio Nuccio’

 

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.

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The potted maple and camellias have become major structural element in the front garden design

05Because 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!

You can hide a cheaper plastic pot inside a nice one

You can hide a cheaper plastic pot inside a nice one

 

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.

Spot the fig!

Spot the fig!

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 good drainage

Use pot feet for good drainage

 

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.

My Nagami cumquat

My Nagami cumquat has roots that grow into the ground below

 

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!

My Shahtoot mulberry needs full sun

My Shahtoot mulberry needs full sun

 

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.

Dappled sun for camellia, blueberry and maple.

Dappled sun for camellia, blueberry and maple.

 

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.

Lettuce naturalised under potted ginkgo

Lettuce naturalised under potted ginkgo

 

4. PLANTING:

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.

Mouse plant growing happily under the maple

Mouse plant growing happily under the maple

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 are incredibly greedy and need regular feeding

Citrus are incredibly greedy and need regular feeding

 

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.

Using Miniscape drippers in pots

Using Miniscape ‘shrubblers’ in pots

 

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.

Turn your potted plants when they grow bare on the shaded side

Turn your potted plants when they grow bare on the shaded side

 

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.

 

 

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Helen McKerral

About Helen McKerral

Horticultural journalist, photographer, contributor to many garden magazines, and author of 'Gardening on a Shoestring'. Adelaide Hills, South Australia

16 thoughts on “How to grow plants in large pots long term

  1. Pat on said:

    Energised by your comments. I grow trees in pots – my cumquat and one camellia have been with me for over 36 years. Also have a kafir lime for 17 years and 2 figs plus a little gem. So many comments are along the lines – too much work.

    • helen mckerral on said:

      Hi Pat, I agree that it’s NOT too much work (if that is what you meant?). I think that the key is to get everything right initially, which takes a bit of organising, but once it is all set up a large pot is actually easier to manage than a small one.

      Thirty-six years for a camellia and a cumquat – I’m impressed! What diameter are your pots? As for “Little Gem”, I have one in the garden that should be called Big Gem, as it’s about 4m tall!

  2. Hello Helen, I have 2 enormous pots on front porch area which faces north & can become very hot due to the verandah being light colour perspex & living at Nhill, we do get hot north winds & it can be very taxing on plants too. I thought I had planted 2 hardy spindly leafy dark leaf plants which were ok for awhile but then kicked their heels & withered up on me so pulled them out. Would Maples be ok to have in these large treated pots. Need something refreshing at front door & your expert advice please.

    • helen mckerral on said:

      Hi Helen
      Japanese maples will fry in a northerly position in your neck of the woods. Not sure of the exact size of your pots, but you could try citrus (maybe variegated cumquats if you want pretty foliage as well), dwarf lillypillies, cordylines, fig, bay tree, ornamental grasses, agaves, desert lime, lavenders, pelargoniums, bouganvillea, and many succulents.

      • classy on said:

        Thankyou Helen, as that gives me something to go on when in nursery next. The lillipillies sound good. Just couldn’t get my head around anything.
        Regards
        Helen of Nhill

  3. Camille on said:

    Hi Helen
    I have a south front garden bed (behind the letterbox) that I was planning to plant 2 trees in but have now been told the gas pipe for the house runs underneath that bed so can’t have roots there – therefore I am considering placing big pots for 2/3 trees/shrubs there instead. This bed does get a southerly wind coming through and we are on the coast in Busselton Western Australia. I have seen images of the Ixora -chinensis-Prince of Orange which looks great, and should I go a lemon or an ornamental pear or a silver birch? I was wanting to screen the neighbours yard. The bed is 2m long and I would put the pots on big pavers – (poss planting strawberries around the pavers… Is this too out there? What do you think? Any advice greatly appreciated.. Kind regards Camille

    • Camille on said:

      Sorry – or a camellia?

      • Linda Green on said:

        Hi Camille
        As a fellow West Aussie I can advise that the winters in our south west are too cold and wet for Ixoras to be successfully grown out in the open. They can be OK in a north facing patio area as long as they don’t get too wet in winter but are kept fairly moist in summer.The lemon tree should be fine as long as it is in a sunny position. The ornamental pear and silver birch are both deciduous so don’t offer much in the way of screening during the winter. Silver birches dry out very quickly during our hot summers and usually die after a year or two even when planted in the ground. There are some camellias that are quite tough, once established – a specialist camellia nursery should be able to advise you which ones do well in your particular site. Camellias generally aren’t that fast growing so you may be waiting for a while before they form a screen.
        Some hardy, fast growing options are Metrosideros Fiji, Syzygium Big Red and Talipariti (syn Hibiscus) tiliaceum rubrum. These, and the lemon tree, all grow fairly large so it may be that you only need one pot instead of two. One large pot with two smaller ones may look more balanced than two of the same size planted with different plants. Duranta Geisha Girl doesn’t get quite as big but is fast growing and very pretty. Your local nursery should have a range of other suitable plants.
        Prune the plants so that they don’t become too top heavy and avoid tall tapered pots to reduce the chance of them blowing over when that southerly wind comes through.
        Strawberries planted between the pavers sound great.
        Linda

        • Camille on said:

          Thankyou so much for your very comprehensive response Linda! Really appreciate your time and effort and will def follow the sound advice given xx

        • helen on said:

          Thank you, Linda! This query slipped by and you have answered beautifully!

  4. Michael Perryman on said:

    Thank you Helen for a really great article.
    I’ve been growing roses and fuchsias in Canberra in very large (75cm) pots for about 3 years since I retired and this year I put them on a dripper system. They really thrived but now I think I have a real problem with water logged pots. I’m sure inexperience in the original potting stage has led to poor drainage. The pots are raised on feet.
    I used full depth potting mix except for about 5cm gravel in the bottom covered with a piece of filter fabric to stop it clogging. I’ve hand scooped down to the bottom of one problem pot and found the fabric clogged and also the gravel also quite clogged with potting mix. Water could literally not get out!
    What pots I could move are now on their side draining and I’m trying to dry them out prior to re-potting now (in 30+ degrees) or in autumn (when the roses will have died from drowning) – dilemma.
    Can you please advise me on how to prepare the bottom layer(s) when refilling the pots so that they will actually drain for the next 20 years??
    Alternatively refer me to a potting-for-dummies site.
    Kind regards, Michael

    • helen mckerral on said:

      Hi Michael

      Modern potting mixes don’t require gravel, “crocking” or screens – just use the potting mix and nothing else. This is what I have done with all my pot plants, and I’ve never had a problem. Avoid “budget” potting mix. You don’t need the super dooper stuff with water-holding crystals, bells and whistles; the most important thing is that when you water it, it drains freely without water pooling on the surface.

      Choose pots with multiple holes if possible. Even when holes are quite large, potting mix won’t fall through. The only time this happens in a big way is when ants or slaters set up house in the bottom of your pot. You will need to treat them, or all your soil will be excavated away!

      I’m not sure about your fuchsias, but in winter when roses are dormant, you could wash the potting mix off their roots, trim them neatly, and repot as described above, spreading the roots over a cone of mix in the pot, and then backfilling.

      Hope this helps!

  5. Deb on said:

    Thanks so much for your potting advice, much appreciated, I’ve learnt a lot and realising why my Meyer Lemon always looks a bit yellow 🙂 need to fertilise more. It’s in a half wine barrel. I’ll put it more in the sun too. My question is I have a Tiliaceum Rubrum (you mentioned in one of the answers). I’m scared its going to grow way too big, I planted it in the ground hoping I could keep it a shrub. Do you think I could keep it small by pruing regularly, or should I get it out the ground and keep in a pot to keep it small. I’d really appreciate your advice. I’m in Vale Park in Adelaide. Thanks!

    • helen on said:

      Hi Deb
      Linda included the reference to Tilia in her reply, and I’m not very familiar with the plant as I’m in the Hills, not the Plains. However, I believe regular pruning will work, especially if you begin when the plant is quite young, so branching develops early. Later you can just take the hedgeclippers to it! It’s also very hot any dry on the Plains, which should help because it’s not in its ideal environment so shouldn’t reach the extreme heights it does in the tropics.

  6. H Lam on said:

    Hi, loved reading this post as I’m growing a few dwarf citrus trees. I was wondering if you have or can put up a post with step by step instructions on setting up a shrubbler for pots with timer, and where to get the items from? Thanks again and much appreciated.

  7. H Lam on said:

    Hi, can I also please ask where you got your terracotta pots for the Camilla and the pot for the fig tree? Thanks

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