On Christa's blog (Calendula & Concrete) a newbie veg grower asked :
'how to calculate how many plants you need based on how much you eat. I can't seem to find any good rules of thumb.'
It's a good question and one you can answer the better with experience. Most seed packets will tell you how best to sow but not how much to sow. So here are my rules of thumb (weather, blight and pests excepted) based on growing and cooking for two. This will yield plenty for the table, some for the freezer and a bit left over to give away.
Potatoes: PD (pre-diet),when we were holding our own in the heavyweight division, most days we'd stare across a mountain of spuds on the table (it's a genetic thing - you can take the Paddy out of Ireland but not the spud out of the Paddy). Now its measured at 5oo grams (that's about 2 good sized Golden Wonder or five to six Charlotte or other small salad types) and we don't have them every night. As for planting I've found each seed potato yields between eight to 12 potatoes at harvest time (some heritage varieties a little less). This year I'll sow at least three 30 foot rows.
Peas: I grow them to eat fresh and I'm not trying grow enough to preserve or freeze. So I can have a three to four week supply with two ten foot rows of mange tout/sugar snap types and two, four cane wigwams, of Alderman (very sweet and very tall shelling variety).
Raspberries: For eating fresh off the cane and freezing for later in the year. I planted ten canes of Autumn Bliss, a late variety that fruits on new growth (pretty much thornless) so you can have a harvest the year you put them in. They've had little care apart from some thinning and I've just cut all the canes down to ground level, a job I do each January. No fiddly messing about with new and old canes. A little manure and they'll be off and growing producing an abundant crop in August and through to the first frost. Plenty to eat there and then and lots to freeze as well. As a bonus they don't need much tying in as the canes support one another.
Tomatoes: Last season was a poor one. But we'd still plenty to eat fresh from three Golden Sweet plants, three Illdi and three Gardeners' Delight. The San Marzanos did poorly but I did get a few tubs of sauce for the freezer. This year I'll plant more San Marzanos the sauce was so good and rich and as an experiment I'm trying to get something from the saved seed of a store bought canned tomato...just to see what grows, if anything.
Courgette/Zucchini: Two plants are plenty, one in the garden I harvest almost daily; the other on the allotment I get to once a week and in peak season there will always be a monster lurking under the leaves. Great grilled and for soups and hash.
Beans: Mostly climbing types. Four, four cane wigwams planted with green, purple and yellow varieties gave ample fresh beans, plenty to store and enough seed for next year. I don't plant for dried beans. On alternate years I'll sow a fifteen foot row of broad beans and get four or five small servings out of this. I also put in three dwarf/bush bean plants (yellow as it brightens the plates)dotted about the allotment where there is space - they don't take up much room at all.
Chard: Ten plants growing, sow seed for 15 and thin down. Will reduce this amount this year as we aren't using enough.
Carrot and Parsnip: I've not had much luck with either so this year I'll try extra hard. I've been harvesting parsnip Tender & True from two 15 foot rows since mid December and there are probably two more servings in it.
Kale: I transplant at least 12 plants from the seed bed to grow on. I'll do more next year as I'll probably not grow grellos again. As to why, think furry teeth and cold strong black tea.
Brussels: Plant out at least 12 plants. Eat the tops as well when you've finished with the buttons. This year the red brussels (four plants) failed so we've a 'shortage'! I much prefer growing them to other cabbages - pick as you need them, they freeze well and so far they've not had any slug damage.
Purple Sprouting Brocoli: I've had six plants in since last April I think. So it'll be almost a year before I harvest from them and I've no idea what they'll yield. Anyone guess?
Grellos/Turnip Tops: A ten foot row still stands in the garden and it probably won't be touched. Maybe I planted these a little early (mid August) and that explains their bitterness even after cooking them with some sugar and garlic.
Lettuce: Over the years I've tried many varieties and made my own mixes but I've now settled on 'cut and come again' growing using the lettuce mixes sold by Franchi (Seeds of Italy). Ten foot rows successionally sown give plenty. I've lots of praise for Franchi - good tasting crops, generous sized packet and a fair price.
Parsley: Ten plants of flat leaf parsley has filled several trays of pesto in the freezer. They get two or three 'haircuts' in the season. This year I'll go for double the amount.
Rocket: The wild type by Franchi is the one I swear by. Two ten foot rows are plenty. I do cut and come again with them also and make pesto for freezing. Also sow successionally as it's quick to bolt when there is any heat about.
Coriander/Cilantro: Grew four plants reasonably well this year and cut them down before bolting and froze as a pesto (got two ice cube trays worth). Great with fish and squid pasta.
Aubergine/Eggplant: Six small fruits off two plants grown outside. This year I have a greenhouse so I may try again but it's a lot of work for a vegetable I don't have that often. (Thouygh if I'd had more I'd have eaten them - just think garlicky baba ganoush. I think I'm better off not trying to beat the weather and concentrate on growing something more suited to conditions here.
Onions, Leeks, Garlic: Most of our meals have one or more of these. I know onions are cheap to buy but I like growing them and I'm almost obsessional about the number of ingredients coming from the garden in each meal. I use sets not seed for ease: this year 1kg white onion sets, 250grams red; 6o leek transplants. I've sown 13 varieties of garlic - plenty for those 40 clove chicken recipes.
Fruit trees: The espalier pear returned 22 fruits this year, up on 18 last year. At the new house we've inherited some ancient plums, damsons and apple trees so we'll have to see how they do. They are not dwarf or trained in any way so harvesting will be a challenge.
Odds and Sods: A couple of mint plants in pots to stop them invading; a couple of pots of chives, one rosemary bush - its belting away so were profligate with branches of rosemary in the roasting tin; one oregano bush; one bay tree (unlimited supply of bay leaves which also double as curry leaf when the recipe calls for it) and I'm still getting chillies from the three plants I dug up and took inside to overwinter - two yesterday with five green chillies coming on.
Squash: Two tiny unripe butternuts off 6 plants. Weather victims.
All this writing about crops is making me hungry. I'm off to cook.