Weeks to Days

The Packet Is Printed in Days, Your Sowing Plan Is Drawn in Weeks

Every seed packet carries a number printed in days — 25, 55, 85 — and every planting plan ever drawn is ruled off in weeks, because weeks are how often a grower actually gets into the beds. So the first thing anybody does with a new packet is divide, badly, in their head: is 55 days eight weeks or nine? The answer decides whether a crop finishes before the first frost or sits in a cold October bed, and it decides how many rows you can fit into one season.

Conversion factor: 1 wk = 7 d exactly, so multiply weeks by 7. A squash block pencilled in for 14 weeks occupies the ground for 98 days — which is why it goes in once and stays, while a 3-week radish row turns over every 21 days.

Where the Two Counts Come From

Breeders publish a day figure

Days to harvest is a trial average from the variety's own breeding records. It is a single integer with no room for a range, which is why two packets of the same crop can differ by a fortnight.

Growers plan in visits, not in dates

Sowing, potting on, transplanting and picking happen on the days you are actually there. A plan built in weeks survives a wet weekend; one built on exact dates does not.

The clock starts in two different places

For a direct-sown crop the count runs from germination; for anything raised in modules it runs from the day the plant goes into its final bed. Weeks spent on a windowsill are not inside the packet figure.

Warmth sets the pace, not the calendar

A packet figure assumes a decent season. The same variety sown into cold April soil gathers heat far more slowly, and eight plan weeks can quietly become eleven.

Working a Sowing Plan Backwards From the Frost Date

A season plan is almost always built in reverse: start from the date the crop has to be off the ground, then count backwards, one variety at a time.

Enter the weeks your plan gives the crop

Type 6, 8 or 14 into the left field and read the days beside it. Fractions are fine — 7.5 weeks comes out as 52.5 days — and a comma is accepted in place of the decimal point.

Count that many days back from your last safe harvest

Take your average first-frost date, subtract the day figure, and you have the last sensible sowing date for that variety. Add slack for autumn crops, which slow down as the light goes.

Space out the succession sowings

Convert your chosen interval the same way — 2 weeks is 14 days, 3 weeks is 21 — and mark those dates in advance rather than deciding each time. Regular gaps are what keep a bed producing instead of arriving all at once.

Swap the direction when you are reading a packet

The swap button (↔) flips the pair to d → wk, which is the way round you need standing in a shed with a packet in your hand: 85 days is a shade over 12.14 weeks, so block out twelve and a half.

Transplant offset: for module-raised crops the packet count starts at transplanting, so add the raising time separately — commonly 4–6 weeks for tomatoes and brassicas. Convert that block on its own and add it to the plan rather than folding it into the packet figure.

Days to Harvest, Crop by Crop

Round week blocks as a plan would carry them, the exact day count each one represents, and the range you will actually see printed across varieties of that crop.

Crop	Block in the plan	Days (× 7)	Typical packet range
Radish	3 wk	21 d	22–30 days, direct sown
Spinach, baby leaf	5 wk	35 d	30–45 days, cut and come again
Leaf lettuce	6 wk	42 d	40–50 days; hearting types run to 85
Bush beans	8 wk	56 d	50–60 days from sowing
Carrot	10 wk	70 d	60–85 days depending on type
Tomato	11 wk	77 d	65–100 days from transplant
Winter squash	14 wk	98 d	95–110 days, one cut only

Read that as a shape rather than a schedule. The top three rows turn over several times a season and are the ones worth sowing in succession; the bottom two hold a bed from spring to frost and have to be planned around, not through. The carrot block at ten weeks is the pivot — long enough that a late sowing will not finish, short enough that an early one leaves room for a catch crop behind it.

How This Pair Earns Its Place in a Season Plan

Plan weeks become sowing dates

Both fields update as you type, so a block typed in weeks gives the day count you subtract from a frost date without stopping to work anything out on paper.

Read a packet the other way round

Swapping turns a printed 55 or 85 days straight into the week block it needs on the plan, which is the direction you want when a new variety arrives.

Months and years for the slow crops

Both dropdowns search across every time unit, so asparagus beds and fruit bushes counted in years sit in the same tool as a three-week radish row.

A clean number for the garden calendar

The copy control hands over the digits with no unit attached, ready to drop into a spreadsheet column of sowing dates. Ctrl + C in a field does the same.

What Growers Ask About Harvest Timing

Does the day count on a packet start at sowing or at transplanting?

It follows how the crop is normally grown. For anything direct sown — radish, carrots, beans, salad — the count runs from the seed going into the ground, or more precisely from the seedling showing its first true leaves. For crops raised in modules and planted out — tomatoes, peppers, brassicas, squash — the count starts on transplant day, and the four to six weeks on a windowsill are extra. Get this wrong on a tomato and the plan is a full month short.

Is days to maturity the same thing as days to harvest?

Packets use the two phrases interchangeably, but harvest is the honest one: most vegetables are picked well before botanical maturity. A courgette is eaten immature, a lettuce is cut before it bolts, a beetroot is pulled at golf-ball size rather than left to swell. Treat the printed figure as "first pick", not "the crop is finished" — for cut-and-come-again leaves and for beans it is the opening of a picking window that then runs for several more weeks.

Why did a 60-day crop take 80 days in my beds?

Because plants run on accumulated warmth, not on the calendar. Growing degree days add up how much each day spends above the crop's base temperature, and a cool cloudy fortnight contributes almost nothing to that total even though it still costs you fourteen days. The packet figure comes from a trial season in reasonable conditions; an early sowing into cold soil, a shaded bed or a run of dull weather all stretch it. Sowings made after midsummer are stretched a second way, by falling day length, which is why the usual rule of thumb is to add roughly a week to any block finishing in autumn.

How far apart should succession sowings go?

Most growers settle on 7, 14 or 21 days, and the right choice follows how long the crop holds once it is ready. Radish and salad leaves go over within days, so a weekly 7-day gap keeps supply steady without waste. Beans, beetroot and carrots stand in the ground for a while, so a fortnightly 14-day interval is enough. Anything harvested once and stored — onions, winter squash — is not a succession crop at all. In late summer stretch the interval, because each successive sowing takes longer to finish than the one before it.

How many weeks before the first frost should I stop sowing?

Work it backwards per crop rather than picking one cut-off date. Take the variety's day count, add roughly 14 days for the autumn slowdown, and count that back from your average first-frost date — a 6-week lettuce therefore wants sowing about 56 days before frost, while a 10-week carrot needs around 84. Tender crops must be finished before the frost arrives; hardy leaves, leeks and brassicas will sit through it and simply stop growing, which is why overwintering sowings are timed to reach near-full size before the light fails rather than before the cold does.