Acacia in pots (London, UK) - advice

[iko]

Hi all,

Long time lurker, first time poster here.

I have been trying to grow Acacia dealbata in a pot in a London terrace for a few years. I am now going through the second plant, first got completely dry in winter! It grows into big trees in London but I'm struggling to make it flower properly or make it survive a few years in a row. Looks like the roots overtake the big pot in a couple of growing seasons and the flowers dry as soon as spring starts (see picture).

If the root bound is the problem, and given it's already in a big pot, I'm considering another Acacia species to replace this. I like the folliage of A. dealbata but I have heard A. boormanii doesn't have such aggressive root system and flowering is quite spectacular, any advice on this please? Thank you!



*Currently in a bigger pot than the one shown in this photo and still same problem.

[MartinNicklin]

I've had the same problem with the same trees in pots. I've had two die and, not wanting to give up because they are so bright and exotic looking, I bought another two last year in full bloom. I kept one in a pot and planted the other in the ground in my greenhouse. Lots of flowers on the one planted in the ground but NONE on the one in a pot. I just wonder if some plants aren't suited to pot culture. I could never grow a decent Fatsia in a pot either. I think you did very well to get so many flowers on that one! I first fell in love with this tree when I saw one in full bloom in Hyde Park many moons ago.
Incidentally what is the church you have a fine view of there? It's on my bucket list to visit as many city of London churches as I can!

[Chad]

Welcome Iko,

I see you live in very central London; St James's Church, Clerkenwell is behind your Acacia I think.

I haven't grown A.boormanii, so my comments are on dealbata.

It wants to be a large tree, so to grow it in a pot you are, to some extent, aiming to bonsai it.

Even then it is not a long term proposition, but you should be able to get 5 years of flowering out of it, and then start again from seed.

To stop the roots going round and round and getting root bound, try growing it in as large an air pot that you are happy with. They are designed for drip watering, so you may want to install an inverted, bottom removed, bottle when you do the potting. It can be filled with water daily and once the compost is 'all roots' it will take a while to empty and should moisten most of the compost.

The top growth needs regular hard pruning just after flowering to keep the top and the roots in balance. If you can get it to be shrubby, then remove a third of the shoots from the base and a third off the top each year. If it persist in trying to be a tree it will need stooling, perhaps every other year.

This is a tough life for a tree, so don't forget to feed it, but not with much nitrogen.

Chad

[MartinNicklin]

Thanks for the advice Chad as well as the church ID. Just been looking it up as Clerkenwell is not an area I have visited. Very nice.

[iko]

@Chad, well spotted! It's St James's Church indeed.

@MartinNicklin, worth a stroll but don't expect grandeur in this area of London. I'd recommend to visit during the Clerkenwell Design Week. The area is actually home to more creative businesses and architects per square mile in the world. Now also with the add-on of a few hipsters exploring after the BBC named it best place to live in London only a week ago.

Returning to the Acacia pot-bound... I'm happy to hear I'm not the only one with this problem and seems to confirm my theory about the plant in need of space to expand its aggressive root system. I have been looking online and found some dwarfish cultivars named A. dealbata 'Nano' and A. dealbata 'Pendula', a wepping form. Sold out in the UK, these are easily available in France, blame Brexit.

Because this is already my second A. dealbata, and I already previously cut roots with a saw when repotting and did some hard pruning after flowering, I'll give a second life to this tree. I'll plant it in a garden and will look into one of the small cultivars or try the A. boormanii for a pot.

PS: I'm looking at the air pot thing. Not sure if I'll use it with this plant but interested to find another plant to use this.

[Chad]

In the recent Australian joint seed order there were some interesting 'dwarfs' bought by people.

Later this year watch out for Acacia alata var alata, A.acanthoclada, A.aphylla, A.applanata etc - if people get them to grow that is!

If you want to keep the leaf type of A.dealbata then A.baileyana, with either green or purple leaves, is a smaller growing Acacia, and widely available.

Which reminds me, I need to sort out the costs of the orders and then they are ready to post.

Chad

[Paul S]

I have no experience of growing acacia in pots but A. boormanii is my pick of the acacia species I have grown/currently grow. It is in full swing outdoors at the moment - has been for over a month - and a haze of yellow. Foliage is wispy and sparse, the plant itself doesn't get huge so I can imagine, but do not know, that the roots being less demanding.

There is an imposter doing the rounds, sold as A. boormanii, that has shorter, slightly wider and bluer 'leaves' and smaller flowers of a richer yellow. Mine is but a youngster so I can't make comparisons but it is certainly trying hard to impress.

Pics from a month ago:

Acacia boormanii



Acacia not-boormanii, not quite fully open



Side by side, A. boormanii to the left