I grow the blanching varieties and use 4 " dia sections of the brown waste water pipe to do th blanching . first height is 6 " second height is 12 inches .
There is no need to do all that hard graft of digging a deep trench in November filing it with well roted manure & put three inches of soil over it & keep having to collar & bank up unless you have crap ground that need a dam good digging over . If you do you can grow your early spring greens transplants or early salad crops on the dug out spoil till the middle of April or so .
In November I simply dig out a 18 inch deep 9 inch wide trench , fill it a foot deep with a mix of well rotted cow muck c/w the urine soaked straw & well composted garden veg waste & cover it with a small ridge of soil , putting a pegged line down the middle of the ridge to help me later on when I plant out.
This will become both food & a good water reservoir for the celery .. any change in the moisture levels will be reflected in the plant very quickly .
Bean beds are made the same way with an inch thick layer of old newspaper on top of the manure then they are covered in six inches or so of earth .
Raise your celery seed starting around the end of FEB on top of the growth medium no covering it over with compost or vermiculite put it under a glass sheet over a sheet of white paper & leave it in warm day light . It takes 18 to 30 day to germinate , transplant the sprouted seed when they are about 2 inches long into 3 " pots ..they tend to get very matted together & are delicate , so be careful to do it indoors at a table using a needle & the handle of a tea spoon .
By about Easter when the transplants are about four inches long , on a dry day walk along the bottom of the tench to compact it a bit , most of the compost will have rotted down . Use a dibber & string line to set the holes five inches apart drop a plant in each hole and like leeks water them in down the hole, don't back fill or press hard on the side of the hole .
If you are earthing them up , when the plants are showing about nine inches of stalk above the trench floor , wrap a paper collar around each plant and gently & lightly tie off with raffia , back fill the hole to about three inches from the top of each plant , repeat when another six inches of growth has arrived & again for the next back filling each time .
If frost is threatened give the plants a six to nine inch blanket of netted down fresh straw ( not hay ) to stop them being hit hard by a sharp frost . You can leave it in place if snow is about to arrive . As straw insulates you can often easily dig a plant out when the rest of the garden is frozen rock solid ,just put the straw back over the rest of the plants , re -net & stake it down again.
If you get it right and the slugs don't eat them you can have fresh home grown celery on Boxing day with home cured ham salad & various home made pickles . it's a far better taste at that time of the year than any commercially produced stuff can ever be.
A sprinkle or two year of old well weathered coal fire soot around each plant and the tubes outside helps keep slugs away . Nematode control works but is expensive to do four or five sessions per year .
Celery leaves cut off the hand of celery can be sprinkled on a baking tray and left in a cooling oven. Turn them around several times in the first hour and leave then in the oven with the door closed over night, Done so they are dry and cool in the morning . Hand rub these dried leaves use the results in soups sauces & omelette's, slip a teaspoon or three of the rubbed celery in a small jar of good quality olive oil , use a teaspoon of the seasoned oil for seasoning a frying pan prior to browning stewing meat etc. or frying sausages .
Small vacuum packed & heat sealed packets of dried hand rubbed celery leaves keep for several years , even longer if you store them in the freezer .