Introduction
 
If you're looking for an easy crop to grow that's relatively fast from seed to cropping, try a turnip!  Turnips have a bit of a bad reputation as being unfashionable, and woe betide the parent who suggests to their children that they have turnips for tea - you'll get looks that could melt the polar ice caps.  However, with a bit of cunning, turnips can be easily disguised if needs be and make a tasty addition to home cooked foods.  Right, lets get growing.
 
Background
 
Turnips are related to cabbages believe it or not, as they are in the brassica family which involves Swedes and sprouts too.  They're not massive in size, but if you let them get too big they go "woody" and aren't as palatable as younger, smaller turnips.  Also, the leafy tops can be eaten as a salad veg or can be steamed and had like spinach. In the early nineties, turnips suffered their worst ever public relations crisis when the then England manager, Graeme Taylor, was turned into a turnip headed characature on the back pages of a popular tabloid newspaper. I thought this was very unfair to the turnip.
 
Growing your own
 
This is the easiest part - getting your kids to eat them will be much harder!  Plant the seeds from late march onwards about a centimetre deep in rich compost, and don't let them dry out.  Brassicas don't like having their roots disturbed so plant them directly out where you want them to grow.  Put each seed about ten to fifteen centimetres apart, with fifteen centimetres between the rows.  As with most plants, weed between the rows regularly unless you're a mother earth type and are in to "permaculture" - an adjective for "lazy gardening"!  Keep moist but not drenched, and within about 6 weeks you'll be pulling your first turnips out, which will be smaller than a tennis ball but bigger than a golf ball.  If you want a steady supply of turnips over the growing season, plant some more seeds out every fortnight or so.  
 
The type I always grow are called "purple top milan", and have a lovely white creamy bottom and a bright purple top, with creamy white flesh underneath the skin.  Allow me to come across all poetic here, but they do look ever so pretty with their purple tops just showing above the soil under a bright green leafy crown; there aren't many purple vegetables so it's good to see a bit of colour in the vegetable garden.
 
You can get seed packets really cheaply if you shop around - Ive found that Wilkinson's own brand are just as reliable as more expensive types for a fraction of the cost.  Also, you'll probably get an average of a couple of hundred seeds per pack, so that's superb for value for money if you were to buy fresh turnips from a supermarket instead.  Also, with growing your own turnips as opposed to shop bought ones, you know exactly what chemical treatments (if any) have been applied to the soil.
 
Diseases / Pests
 
Being a brassica, they can be prone to club root, but this is easily prevented by growing them in raised beds if you suspect your garden has club root in the soil.  Any soil you intend to grow turnips (or any other brassica) in should be free draining and slightly alkali - club root thrives in wet acidic soil, so by adding plenty of grit and lime to your soil or compost you can alter the conditions favourably.  
 
Turnips can also be affected by cabbage root flies.  It's not the actual fly that does the damage, it's the maggots that hatch from the eggs they lay.  These maggots will burrow through the soil and eat into your turnips, which will ruin your crop for eating and kill the plant eventually.  The best way I've found of preventing this is to prevent access to the flies themselves, by covering my crop with a light horticultural fleece.  The fleece should be able to let light and water through, but not pests, so don't be tempted to use plastic sheeting as this won't allow any water to get through.
 
Using turnips
 
I once learned the hard way that turnips don't keep very well in certain conditions.  I'd pulled a load of turnips out of the garden one day, lovingly washed all the soil off and dried them, wrapped each one individually in newspaper and stored in a dark cupboard.  Very diligent and very organised food storage, the perfect method for surviving zombie outbreaks and nuclear winters.  Two weeks later I went to my stash, only to find that they had dried out and withered down to the size of a grape!  They were completely unrecognisable as turnips and at first I thought my wife had played a trick on me.  From then on, I now only ever cook turnips fresh from the garden or peel, blanche and dice them before throwing into food bags and deep freezing.
 
I add diced turnip into stews and soups - the kids don't seem to be able to distinguish it from diced potato in the same dishes, so I can get away with adding a bit more variety into their diet in a sneaky way!  It also makes a good substitute for swede, goes well with carrots, and for a really hearty mash, try mashing turnips with potatoes and celeriac.  
 
 
Summary
 
Spring is nearly with us - if you've got some bubble wrap to cover your soil you could even try planting some turnip seeds outside towards the end of this month instead of waiting till the warmer times that March promises.  Also, as they grow so quickly, you'll be rewarded in next to no time with lots of lovely fresh turnips that you can use to add a different dimension to the average Sunday roast dinner.