It’s too low, it’s unprotected and there’s too much of it: things are not sounding great from the gardening expert. She has come to consider this year’s plan, but she hasn’t yet got further than the gate. A big, low, unprotected expanse of waterlogged and weedy mud greets her — my vegetable patch.

I had hoped that Sarah Wain might overlook all that and go straight to my plan, of which I am rather proud. Nicola (whose garden it is) and I drew it in October, and it covers the whole year from rhubarb to radish, broad bean to butternut squash, in a fearsome grid.

Plot A has spinach and spring cabbage, followed by potatoes and sweetcorn, tomatoes and artichokes; Plot B more potatoes, carrots and parsnips; Plot C beans and peas; Plot D lettuce, rocket, chilli and tomatoes, and so on, all the way to plot I (squashes). We ran out of space before I could put in some aubergines.

But Sarah wants to consider earthier things. Like “organic matter”. You need a lot more of it, says Sarah, who is in charge of vegetables at West Dean Gardens, West Sussex, a rather more professional outfit. A ton or so of manure is spread vaguely around a few of our plots; I cannot now remember why those and not others. It was hell to spread (so heavy) and I don’t want to do any more of it. Nicola unhelpfully broke both arms falling out of an attic before Christmas so wasn’t able to do much. I glance at the donkeys peering bleakly out of their shed and wonder fleetingly whether some laxative and a nice trot around the garden...

Sarah has worse news. Not only do we need to do much more mulching as the year goes on, but the manure we have spread already is going to have to be dug in. This is even harder work, backbreaking and slow. I had hoped, I tell her, that if we spread it in January, compared with last year when we didn’t get it down until March, the worms might pull it all down into the earth by spring. Sarah can’t think of anything at all to say to that. She just gives me a silent, wide-eyed look of astonishment, like you might give a stranger on a Tube who asks if they could just sit on your knee for a little while. She explains later that it’s too chilly for the worms to do much at the moment and the manure itself will keep the soil too cold for germination. So we have to get digging in.

I take the expert to see the remains of the vegetables from last year instead: five admittedly rather manky-looking red cabbages (“I’d chuck those two”), a fair few leeks, some cute rows of garlic, onions and broad beans coming up sweetly for spring. “They need weeding,” she says. Yes, yes, but aren’t the lines nice and straight?

What I know we have done right is planned the rotation: peas and beans (2) after potatoes, root vegetables and tomatoes (1), followed by cabbage family (3). I show Sarah the map; lots of 1s and 2s and 3s and scribbling outs and Xs (some vegetables do not need rotating), and A and B and C and all the way to I. With a map like this, nothing can go wrong. “I shouldn’t worry too much about rotation in a new plot like this,” she says briskly. “It’s not as important as working on the soil. You need to build it up. Organic matter.”

Turns out there isn’t much that we’re not doing wrong: the rhubarb cannot be forced, as we had planned, year after year — it needs to rest for a year to recover — and our green manure, a crop we have sown in a few of the plots to protect the soil over winter, is “not as vigorous as one might have liked”.

Well, what does she know? Last year we did OK. The only thing that didn’t grow was the okra. We had peas and courgettes and spinach, French beans and sweetcorn and fresh spuds. My freezer is still full today of burstingly bright tomato and basil sauce, and tender broad beans. There are some onions left in the shed. And we have eaten delicious butternut squash, carrots and parsnips all winter, while the garden is still throwing up Jerusalem artichokes, cabbages and leeks, and a few pretty, purple Brussels sprouts. If anything, there was too much of everything last year and we couldn’t keep up. My philosophy of vegetable growing is chuck it all in and don’t worry if some of it doesn’t work out. Sarah thinks we should forget growing anything in the sunken plot A, one of the biggest, and work on building it up over the year instead, with compost and manure. We did have a lot of trouble there last year; it was alternately waterlogged and cracked dry. But we can’t just leave it empty: where would the sweetcorn and tomatoes go, and the second load of potatoes? They are on the grid.

“It’s a great location,” Sarah concludes, as the rain and the wind pick up and the South Downs glower at us across the fields. “It has great potential. But don’t be overambitious.”

Ha! We are going to grow: butternut squash, French beans, runner beans, broad beans, peas, red and white onions, spring onions, shallots, garlic, parsley, carrots, parsnips, Jerusalem artichokes, artichokes, leeks, cabbage, lettuce, fennel, rocket, chillies, tomatoes, butternut squash, courgette, pumpkin, sweetcorn, potatoes (six varieties), cauliflower, celery, celeriac, spinach, Brussels sprouts, radish. And aubergines. I know we are. Because it’s all on the map.

Explore Gardens

• Hampton Court Palace Flower Show

• Chelsea Flower Show

Times recommends

• Here comes the glass sun – garden honours Beatle
• Gardening tips: 10 things to know about Horny Goat Weed or Epimedium
• Diarmuid Gavin shares tips on how make your garden fun and funky