9 Seeds Worth Starting in January (and 4 That Will Wreck Your Spring)

I am writing this in the middle of September with the squash still coming in, which is a strange time to be thinking about January. It is also the only useful time. The catalogs land around the second week of December, everything sells out of the good onion varieties by the end of that month, and if you have not worked out what you actually need before you sit down with them, you order by picture.

So this is the list I keep for that afternoon in January when the house is dark by half four and there is nothing to do outside.

What January really means

January is a place on a calendar and your seeds cannot read one. What matters is how many weeks before your last frost a thing needs to be sown, so the real sum is your last frost date minus the number of weeks on the packet.

If your last frost falls in March or early April, January is genuinely the right month for most of what follows. If your last frost is in May, most of this list slides into February and only the two or three slowest things stay in January. The difference between a zone 8 garden and a zone 5 one is six or seven weeks, which is the entire spread of this article.

Get that one number right and the rest of the year mostly sorts itself out. Get it wrong by a month and you are hardening off a root-bound plant in a snowstorm.

The nine

1. Onions from seed

Onions from seed need ten to twelve weeks before they go out, and they need that whole time, because a bulb only gets as big as the plant was when daylength told it to start bulbing. A small plant in April makes a small onion in July, and no amount of feeding fixes it later.

Two things people trip over. Buy the right daylength type for your latitude, long-day in the north, short-day in the south, intermediate in the middle. And buy fresh seed. Onion seed loses viability faster than almost anything else in the box, so the packet you saved from two winters ago is a gamble you take in the one crop that punishes a late start.

2. Leeks

Leeks want the same ten to twelve weeks and are far more forgiving about what happens next. They sit happily in a module, they do not mind being trimmed back with scissors if they flop, and they transplant like weeds.

They are also the best value on this list if you buy leeks in winter. A January sowing gives you the fat autumn types rather than the pencil-thin ones a hurried spring start produces.

3. Shallots from seed

Most people buy shallot sets, which is easy and expensive. Seed shallots cost a fraction of that and store better, because a plant grown from seed does not carry over whatever the set was carrying.

Treat them exactly like onions: ten to twelve weeks, sown in a tray and separated, or three or four to a module and planted as a clump. They are slower off the mark than sets and they catch up by midsummer.

4. Celeriac and celery

Both are slow, and celeriac especially so. Ten to twelve weeks is the usual figure and it is not padded. The seed is tiny and needs light to germinate, so press it onto the surface of the mix and do not bury it, which is the commonest reason a tray of celery seed does nothing at all.

They want steady warmth and steady moisture from the start and they sulk permanently after an early cold check. If you have only ever bought celeriac and been horrified by the price, this is the crop that most rewards the early sowing.

5. The slowest peppers

Sweet peppers are an eight to ten week crop and can wait for February in most places. The superhots are different. A habanero, a scotch bonnet, a rocoto can take three or four weeks just to germinate, and they want soil around 80F to do it, so the clock does not start when you sow, it starts when they come up.

Add that germination window to a ten or twelve week growing period and even a zone 6 garden is looking at mid to late January for those varieties. Bottom heat is the difference between three weeks and never.

6. Eggplant

Eggplant needs eight to ten weeks and the same warmth peppers want, and it hates a cold check worse than almost any other transplant. It is on the January list for warm-zone gardeners and the early-February list for everyone else.

The reason to bother growing your own is variety. Garden centers sell one or two globe types; the seed catalogs sell thin Japanese varieties that cook in four minutes and small white ones that are worth the shelf space they take up in the catalog.

7. Parsley

Parsley germinates slowly and unevenly, and the standing joke about it going to the devil and back before it comes up is roughly accurate for a cold windowsill. Two to three weeks is normal. Give it eight to ten weeks before your last frost and it will be a real plant when it goes out rather than three threads.

Sow more than you think you want. Flat-leaf parsley is the herb most likely to get cut to nothing in July, and a spare plant in a pot by the door is worth more in August than it looks in January.

8. Artichokes

You can grow globe artichokes as an annual and get heads the first year, but only if you do two things: sow eight to ten weeks before last frost, and then give the seedlings a deliberate cold spell once they have a few true leaves. Ten days to a fortnight somewhere around 45 to 50F is the usual advice, out in a cold frame or an unheated porch.

Without that chill they behave like a plant in year one and make leaves and nothing else. With it, you get heads in your first summer off a packet of seed, which for a vegetable that costs what artichokes cost is a very good afternoon’s work.

9. Asparagus from seed

Crowns are the normal way in and they cost real money for a bed of any size. Seed costs a couple of dollars, and the trade is a year: a seed-grown bed starts cropping one season later than a crown-grown one.

Start them twelve to fourteen weeks before your last frost, grow them on in pots through the spring, and plant them out into the permanent bed in early summer. If you have been putting off an asparagus bed because of what twenty crowns cost, this is how the bed gets built.

The four that will wreck your spring

Tomatoes are the big one. They need six to eight weeks, and a January sowing gives you eighteen. What you get is a three-foot plant with roots wound around the inside of a four-inch pot, and it never really forgives you. A tomato sown in mid-March catches and passes a tomato sown in January almost every time.

Squash, cucumbers and melons want two to four weeks indoors and no more. They grow fast, they resent having their roots disturbed, and a leggy cucumber seedling in a small pot in February is a plant you will end up throwing away.

Basil needs warmth it will not get in January and grows quickly when it does get it. Six weeks is plenty. Sown early it goes pale, leggy and thin-stemmed on a windowsill, and it never bulks out the way a later one does.

Beans belong in the ground. Their roots hate the move, they germinate in days when the soil is warm, and every year somebody starts them in February and ends up with tangled seedlings and no earlier harvest for it.

The one thing to do before December

Work out your last frost date and write it on the front of the seed box. Not the neighborhood folklore version, the real one for where you are, and then subtract in weeks from there rather than trying to remember which crop wants which month. Everything above is a number of weeks looking for a date to be taken away from.