I'd get it started about now, as you would for tomatoes, and grow it on in pots until you can plant it out in the garden once all the frosts are past. It needs a long growing season and warmth. Be generous with the water while it's bulking up.

The flowers are a bit like potato flowers but soft yellow. Not flashy. If you have to put it into a flower bed for warmth - put it toward the back. It's not a plant to win admiration.

If it is left in the ground over the winter, the little husks become skeletonised, the fruit withers and the seeds are liberated as the wind shakes the stems. A censer distribution. You could well find it popping up again next year, but it probably won't reach fruiting size in time. You could try potting on some of the seedlings and over wintering to give you a head start for the following season.

You can make jam with them. Not a great set - and anyone with false teeth will not thank you. (Put the mix through a strainer is best.) Personally, I prefer the fruit raw, when it's deep yellow. Pop the husk to check.

When the birds discover what you've done you'll have competition for the fruit.

In the right conditions it can become weedy/mildly invasive. Hopefully, you have enough frost to keep its ambitions in check.

Cape Gooseberry is Physalis peruviana — it's that that's described above, a sprawling (indeed unruly) bush. But there's also the similar Physalis pruinosa which is a bit more compact and, in my view, easier to grow and accommodate. Their fruits are very similar. I find growing either in a container is the best way to keep them tamed. In the open soil they tend to produce shoots and leaves at the expense of fruits. I have three bushes which I overwintered but they are so far making little progress, which is to be expected: they are day-length sensitive and make little growth while days are lengthening.

But there's also Ground Cherry, Physalis pubsescens. Its fruits are smaller, but more numerous and borne in compact plants. It is very attractive.

Tomatillo, on the other hand, is also a Physalis, ixocarpa, producing bumper fruits on stocky plants. I grow lots of these every year. They are easy to grow, high yielding and versatile. The fruits are very savoury, and tangy, no good for dessert like Cape Gooseberry. It is this that is the authentic ingredient in salsa, instead of tomato which has lately come to be used in its place.

But the one to avoid is Physalis alkekengii. It is a hardy ornamental perennial. The fruits are small, foul and actually quite poisonous. I erroneously tried one many years ago and regretted it! Not lethal, but really not very nice.

What I have got is some nice little plants of "Purple de Milpa" tomatillo. Half-price seeds from somewhere! Would these be P. ixocarpa?

Trouble is, it's going to be a squeeze, shoe-horning them into the allotment somewhere. It's got to the stage where nothing can go in unless something else comes out....

Don't suppose this one's decorative as well, is it?

What you bought in the supermarket, as outlined comprehensively by Simon H above, is almost certainly physalis peruviana.

And in Britain they grow differently from the US, because of our much cooler climate. I started mine 4 years ago from supermarket seed and put them in the unheated greenhouse.

They grew quite tall, but did nothing the first year. They died right back and then came up again the following year. I got flowers in late October but in my unheated greenhouse nothing ripened that year. The third year (and also this year) the plant started flowering even before the regrowth was full size. I have already little lanterns developing. Last year they flowered pretty much all sunmmer and I got a good harvest from July onwards. They are delicious and keep for months inside their lanterns. A few fruit inevitably escaped and fell to the ground but I had no self seeded plants spring up from them. I don't know how long the plant will live - it is still looking very good this year.

The other physalis I am growing is ph pubescent. These are much smaller annual plants the size of aubergine plants, which produce smaller lanterns and fruit the size of a large blackcurrant/small cherry. They also grow better in the greenhouse. From a sowing with the tomatoes I now see the first flower buds on mine. Their fruits are delicious too. They drop their lanterns as a sign that the fruit inside is ripe. As a consequence they are said to self seed like mad and become invasive in USA gardens as a consequence, but this has not happened here in the greenhouse. The fruit also keeps for months.

You wrote: I haven't bothered with the orange, husky sort of physalis because I decided I didn't like the taste very much! What I have got is some nice little plants of "Purple de Milpa" tomatillo. Half-price seeds from somewhere! Would these be P. ixocarpa?
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I should have read your further post more carefully before replying to the post on the top of the page ;-)

Yes, these are p ixocarpa. I usually stick them in the greenhouse corner and they grow to 6ft. No special treatment like pinching out or the like, I just water them.

They would flop over on their own, but I keep them upright with 4 bamboos and gardentwine around these. A few plants go a long way because they are quite productive, but I am really not sure how they will perform outside.

Best of luck with them. And yes, you can plant them closely.