Hi Sibe,

I have a Robinia tree, about 4ft tall (1.2m). I'm not sure what species it is, but it has rounded very pale lime green leaves which are soft and fluttery. I bought it from a garden centre about two weeks ago and it is still in its original 12in (30cm) pot, sitting inside a container with pea shingle in the bottom, so it's very well drained. The tree is on my roof terrace which is south-facing but exposed and on the top floor of a three-storey house, so it is open to all elements.

I have secured the main stem to the roof terrace railings with string and water it every night. New leaves continue to come through but some of them are turning yellow, dropping off or just coming away in your hand if you touch them.

Would you be able to give me any idea what is wrong? Am I watering it too much? Or is it getting too much sun/wind etc?

I would be so grateful for any advice you can give as I have really fallen in love with my little tree.

Many thanks,

Hayley

Our Gardening Expert replies:

Hi Hayley,

I can understand you falling in love with this tree, it really is a very attractive type and worthy of a place in almost any garden.

Your Robinia sounds like Robinia pseudoacacia 'Frisia'. This is an extremely attractive tree and is often planted to make a suburb focal point in the garden. The leaves open to a golden-yellow colour in April and May though they do turn a little green towards the end of the summer.

Your plant could be losing leaves because you are over-watering it or indeed because it has suddenly been exposed to the sun and wind. At its previous home in the garden centre it may have been in a more sheltered place. It should soon adapt to its new location but I think the main problem is that it is not really suitable for a roof terrace - for one thing, it's just too big! Although this particular selection is fairly slower growing than the normal type its ideal home would be in a small garden. It's also possible that this tree may have been in its pot too long and the compost is simply exhausted.

It does, however, really need to be planted in the ground, not in a pot. If you really want to keep it in a container then one two or three times larger than the present container is going to be needed - and this may be too heavy for the terrace.

You may also be interested to know that one variety of the Robinia tree that does flourish in pots is the 'Robinia pseudoacacia Lace Lady' (pictured, and available from Crocus). It's a splendid bonsai specimen whose leaves turn a lovely orange-yellow in the autumn and have a striking contorted look in the winter.

All the best,

Sibe

PS For more ideas on trees suitable for your garden, see Away from Prying Eyes, Tropical Trees and Candle Tree.