Save the seed - tomatillos

You can never predict with any certainty which crops will do well at the beginning of the season. This year, the Swiss chard, usually one of my bankers, all ran to seed in May and I was barely able to pick a single leaf. I planted the borlotti beans far too late and despite the fine summer and mild autumn, they never caught up. And the tomatillo seeds inexplicably refused to germinate - I got a grand total of three plants from 20 or so seeds sown.

I always feel faintly amazed when the tomatillo plants grow strong and productive most years - they always seem very exotic in my north London allotment. They are closely related to physalis, or Cape gooseberry, and grow similarly, the fruit maturing within a papery husk (see picture, above). The fruit itself looks like a green tomato, another relative, though the tomato is more of a cousin than a sibling. Tomatillos (Physalis philadelphica or Physalis ixocarpa) have a fresh zingy taste, not unlike either a physalis or tomato without the sweetness, and are commonly used in Mexican and South American cooking, in salsas, and cooked sauces

Thinking about how to ensure better germination rates, I considered saving seed from this year's tomatillos to provide seed for next season. Horticultural lore says that over generations, self-seeded plants will become more and more adapted to the specific conditions in your soil - your terroir, if you like. This is one reason why saving your own seed is so effective (it's also economic and sustainable, but let's just stick with the adaptive advantages for now).

The idea of saving seed from my plants has always been irresistible but there are practicalities to take into account. You should also only save the seed of open pollinated plants. These are plants which either self-pollinate, or which are pollinated by a plant of the same variety. The resulting seeds will then 'come true', ie, produce fruits like those of the parent plants.

Don't try saving seed with hybrid (F1) plant varieties - they won't come true to type. And if you grow more than one variety of a plant - or indeed, if your neighbour does - you may get undesirable cross-fertilisation: the seeds you gather and sow won't then come true to type. Squash and pumpkins are particularly known for this. Even with self-fertilising plants like chillies, it's recommended to isolate the different varieties because they will also cross-pollinate, for example by bees en passant.

If tomatillo seeds can be tricky to germinate, then seeds which you have saved yourself could well be more likely to sprout the next year, the parent plants having thrived in the comparatively cool, damp UK conditions. The plants that grow from the saved seed will then be even more predisposed to do well in my allotment, having been derived from two generations of plants which managed to deal with London clay and the omnipresent bindweed. And so on, through the generations, until the plants are completely at home, strong and reliable and productive. That's the theory, anyway.

I reckoned saving tomatillo seed should be similar to that of its cousin, the tomato. It turns out that it's quite a bit simpler. With tomato seeds, you have to let them ferment a bit, with tomatillos it's a comparatively fuss-free process.

Top left: 1) whizz up your tomatillo fruits in a blender to separate
 the seeds from the flesh; 2) Add water to the tomatillo pulp - the 
seeds will sink to the bottom of the jug; 
Bottom left: 3) Sieve the contents of the jug; 4) spread the seeds out on a plate to dry.

First, choose the fruits you wish to select seed from. These should be fully ripe, large, prime specimens. Remove the outer husk so that you are left with what looks like a green tomato. You need to separate the seeds from the flesh and the best way to do this is to give them a quick whizz in a blender (top left, above). This seems quite counter-intuitive, but it is effective and won't grind up the seeds themselves. If you have a pulse function on the machine, use this to ensure that the fruits get only a brief blitz.

Next, scrape the tomatillo pulp into a jug and cover with cold water (top right). Give the mixture a quick stir. The seeds will sink to the bottom leaving the pureed flesh at the top. You can skim this off and rinse the seeds through a sieve until all the flesh has been removed and you are left with the seeds in clear water.

Drain the contents of the jug through a fine sieve (bottom left) so that you are now left with just the seeds. These should be left at room temperature to dry out: spread them on a plain plate or similar non-absorbent surface (bottom right). DON'T be tempted to spread them on kitchen towel or a tea towel or anything similar: the seeds will adhere to the absorbent surface and you won't be able to pick them off again.

The seeds should be dry in 2-3 days. Transfer them carefully to a paper bag or envelope, label with the variety and the date, then seal and store somewhere cool and dry.

Tomatillo plants won't withstand frost, so you will need to start the seeds off indoors in spring. I usually sow mine in March, either in modules or two to a 9cm pot. They will take around 7-10 days to germinate and can be potted on before being planted out once all danger of frost is past.

I have grown tomatillos in the open ground and also in large deep pots, but it is definitely better to grow them outside. They're not self-fertile and rely on pollinating insects, so you need more than one plant, and bees and the like must be able to access them - which might be as simple as leaving the greenhouse door open, although they seem to like London summers well enough. The open ground plants do grow more bushy and produce higher yields of fruit, but the difference is not so great as to make the pots markedly inferior.

Tomatillo plant in high summer showing both flowers and ripening fruits.

Rainbow veg - Orange is for Physalis

Physalis, or Cape Gooseberries, or Inca berries, (Physalis peruviana) taste infinitely better when picked fresh from the plant then when bought from the supermarket. The taste is sweeter and more complex than the fruits imported from, usually, South Africa and stored before going on the shelves.

Although most of our homegrown physalis gets eaten as an allotment snack, my ambition is to get enough fruits to make physalis jam, which I've heard a number of people say is their favourite.

I’ve been growing physalis for two to three years now and discovered that in the UK it needs a loo-o-ong season. The plants actually did better in the cool summer of 2012 (when we had a bright warm spring) than the long warm summer of 2013 (when the temperature didn’t get much above freezing until well into April). This year I’ll be sowing the seeds indoors in early March and will keep them cosseted and warm, transplanting into decent-sized pots before they go outside once all the frosts are done. I’ve also got a new raised bed lined up for them – hopefully they will reward me for this five-star treatment by producing some beautiful golden fruits come October time. 

Sown in pots in March and kept at an even 20 degrees temperature
until ready to be hardened off and planted in a sunny sheltered
spot outside.

Get Cape Gooseberries. Grow Cape Gooseberries. Fly

I was given some physalis seeds at the beginning of the year. Physalis is one of those fruits I buy occasionally and then never know what to do with them. They look little a small orange tomato, wrapped in a papery case, and I find it very hard to describe the taste - sweet and fruity with a tart note is about as much as I can manage. I didn't feel they would be very appetising cooked. I also wasn't sure why I might want them: physalis plants spring up self-seeded every year, germinating from the kitchen compost. 

So we buy them occasionally from the supermarket and snack on them. A few overripe ones get thrown in the compost and it is presumably these whose seeds germinate later on the allotment - often intermingled with some enterprising tomato plants which self-seed the same way. These 'volunteer' plants never seem to set fruit (the self-seeded tomatoes never seem to get blight, either).

Physalis are related - fairly closely - to tomatillos, and also to tomatoes and aubergines. They're part of the botancial family Solanaceae. Solanaceae is the nightshade family, but don't let that put you off. They're also known as Cape Gooseberries, groundcherries, Chinese Lanterns (usually the more non-edible varieties, grown for the lantern-like seed cases) and improbably enough, golden strawberries.

The one you'll most often see in British gardens is Physalis alkekengi, which is hardy in winter and bears the bright orangey-red lanterns. 

The name Cape Gooseberry is often associated with the edible plant, Physalis peruviana - the 'cape' in this instance isn't a geographical cape harking back to the plant's origin, but the item of clothing, referring to the case which covers the fruit. They grow in sub-tropical and temperate climes, and, I have discovered this year, in a cold wet summer in London. I thought it might be interesting to grow some physalis on purpose and see just how many fruit we could raise. We were also growing tomatillos at the Secret Garden Club and I wanted to make a comparison between two such close relatives. 

I treated the physalis seeds as if they were tomatoes or aubergines: sowing them (a bit late) at the beginning of March, two to a small pot under a cloche, and leaving them to germinate indoors in warmth. The seedlings were up two weeks later, and grew quickly in their pots, uncovered, on a sunny windowsill - see above.

By the beginning of June, they looked as though they might need staking in their pots. I also desperately needed the windowsill space to bring on the pumpkin seedlings and so, despite the fact that it was pouring with rain every day, out the physalis had to go, transplanted to a sheltered, south-facing bed on the allotment (left).                                                                                                                    They grew on vigorously despite the inclement conditions, and yes, by July they did need staking. They also came into flower, the flowers closely resembling those of tomatillos. In fact the general growth habit of physalis and tomatillos are similar, although the physalis are sturdier. The tomatillo plants were almost flamingo-like with their long spindly stems supporting multiple branches. The downy heart-shaped leaves of the physalis are a darker green and wider than those of the tomatillo. 

Physalis flowers: much of the foliage shown here is actually of the neighbouring
comfrey plant. You can also see several immature green fruits developing.

The fruit starts developing inside the green cases in July/August. If you gently squish the green teardrop-shaped lanterns between your thumb and forefinger you can feel the fruit, at first just the size of a pea, then growing bigger and bigger. Unlike the tomatillo, they don't split the casing, but when the husk turns brown from green, the fruit inside is ripe.

An unripe physalis fruit in the foreground, with one ripening behind it.

Trying out the first ripe fruits, the taste was a revelation. Having never eaten a physalis that hadn't spent most of its days in a supermarket before, I was unprepared for any complexity or depth of flavour. But that ill-defined fruity-and-a-bit-tart is so much rounder and syrupy - and yet still with a threat of tartness. Now I can see why you might want to make jams or jellies (and definitely a pavlova) from them. If all physalis tasted like this, we'd do so, so much more with them.