Julie,

I don't know exactly what Bottle Gourds are like, but some of these plants can grow up to 15 ft long (or high, depending on how you train them.)Rather space-consuming in the average greenhouse!

Most of the advice seems to be to grow them as half-hardy annuals, sowing seed in April. I guess the answer is to put them outside as soon as you can, and hope for a long, warm Autumn!

good luck!

Chris

Bottle gourds need lots of heat, and that includes at night. They will only succeed well in a polytunnel or glasshouse, where they are less likely to be chilled at night. They do not need to be started off early in the year, necessarily. It is better to sow a bit later, say beginning of May, when they are more likely to have lots of light and boosting warm days from the start  if early sowings stagnate, that can be detrimental. They really do need lots of space, moisture and a close eye on pests, especially red spider mite. I have a lovely gourd I grew about five years ago. It is quite dry and the seeds rattle within. I guess as long as it is kept dry it will never deteriorate.

I grow bottle gourds and birdhouse gourds here in Southwestern Ontario, Canada. They do need warm conditions and a longer growing season to set fruit and have the fruit mature enough that they cure properly instead of rotting. I grow them outdoors, uncovered and train the vines up a trellis made from old wire and pipe gates.
We get killing frosts around mid-Oct. I leave the gourds in the garden on the vine until the vine is thoroughly dead then gather all the gourds up and set them aside to cure. I have cured them in my basement successfully but they do get mouldy as they dry (which is a normal part of the process) and I hate to introduce mould into my home. So subsequent harvests have been left outside all winter to cure. They sit under snowdrifts, freeze and thaw for months and withstand temperatures of -25* F....and still successfully cure and are a nice hollow vessel in the spring with the seeds rattling round. I will however place them up off the ground this winter as I found the bottoms were holding moisture for far too long. I think they just need a little more air circulation.
It's probably true that kept dry the gourd will never deteriorate, Simon. But I had one that for some odd reason got left in the vegetable garden for several years. It had cured into a hollow shell and we just kicked it about the garden like a football whenever it was in the way! It stayed outdoors through all weather and our Canadian winters for several years in good shape. But this spring I went to pick it up to show someone and my fingers went right through the shell and I finally pitched it in the compost bin!
Hope you don't mind me snooping over here in the UK forum. I like to read about gardens and growing conditions in different countries and look forward to doing some garden touring in the UK someday.