Those particular arums are not really hardy, and should be treated as tender bulbs. They should still grow and flower ok later in the summer but you risk losing them if left out all winter.

For best results, these require starting into growth indoors then moving outside once all danger of frost has passed.

Moriati

I agree with Moriati.These must be treated as half hardy. Several varieties do appear hardy in Wales but not all. Here in Pembrokeshire we do have to lift the slightly tender types.
Best wishes,
Gerald.

I've seen white arums growing in great sheaves of glossy green leaves in Pembrokeshire, in early Spring so they must have overwintered well in that mild climate. Are they Z. aethiopica? I grew one like that once in Leicester but it died that winter. Are the coloured ones the same species but a distinct variety?

Having got away with it this winter I'll leave them out until November, then lift them. They can bunk up with the dahlias and cannas.

I have a huge Arum Lilly that my mother in law gave me a year ago, it is white and was in a large pot, i put it in the ground and it has gone absolutley mad, it has 12 flowers on it at present and i cut off around 5 at the weekend. It is in dapple shade and i give it plenty of water in the spring and summer and feed it fortnightly. I didnt cover it in the winter just gone as i forgot! the leaves got badly frost damaged but it survived. Im not sure what kind of Arum it is though.

Lou xx

Maybe you planted them too deep? But if you have found healthy looking root buds, plant them again about 3" deep, and you'll surely get some plants showing soon with flowers later on.
They usually flower about this time, and when I cut off the spent flowers I get more and more.
Here in Ireland the white Zantedeschias are quite hardy, but then our climate is rather mild.
For best effect plant in clumps. You'll get so many that you can easily divide them next year.

They're up! Everythings growing like a rocket after Friday's rain.

i grow these in pots and noticed that this year, they were very late into growth but once they start...... I never bother overwintering under cover and they seem to come up, year on year. However, I mainly grow the pink (Rhemannia or similar name) and the white aethiopica rather than the more exotic New Zealand hybrids. They only started showing about 3 weeks ago and now reach around 40cms but no buds yet - but they will come. Well done, garden nerd - patience rewarded!

http://www.windyhillflowers.com.au/index.html?target=dept_44.html&lang=shop

Here are some pictures of ours in oz. I have mine out in winter and they pop up again.

My arum lilies flowered in the spring, then I transplanted them into soil to grow next to the new wooden shed..and a few weeks later, heck they are really sprouting big leaves now !!

Mine is still growing and growing!! Will upload a picture for you when i know how. I tend to cut the leaves back and as they grow over my path and the new ones grow back with a vengence. They love lots and lots of water in the summer and this winter i will cut all the leaves off mine completely and cover it till frost has gone.

Lou xx

I have one with plenty big healthy green leaves but it had just few flowers in early summer. What should I do to make them flower more?
Thanks for advice
Neringa

The arum lilies were affected by (a) frost (b) slugs so I put slug pellets round them and fed with Miracle Gro and a mulch of multi-purpose compost and they are just flowering now :)