Crop Timeline Calculator

Plan when to sow, transplant, and harvest your vegetables. Calculate backwards from target harvest dates or forwards from sowing dates with popular UK crops.

Crop & Growing Details

Your Timeline

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Enter a date to get started

Select a known date above to calculate your full timeline

How to Use This Calculator

1. Choose Your Crop

Select from popular UK vegetables to load typical growing times, or use "Custom timeline" to enter your own timing from a seed packet or variety guide.

2. Select Growing Method

Choose whether you'll start seeds indoors and transplant, or direct sow outdoors. Root vegetables like carrots and parsnips must be direct sown.

3. Adjust Growing Days

Fine-tune the days to transplant and days to harvest based on your climate, variety, or seed packet recommendations. All values are editable.

4. Pick Your Known Date

Select which date you want to work from - sowing, transplanting, or target harvest date. The calculator will work backwards or forwards to determine the other dates.

Common Use Cases

Planning Spring Sowing

Work backwards from your last frost date to determine when to start tomatoes, peppers, and other frost-sensitive crops indoors.

Succession Planting

Calculate when to sow lettuce, rocket, or radishes every 2 weeks for continuous harvests throughout the season.

Target Harvest Dates

Working backwards from a specific date? Enter your target harvest date to find out when you need to sow for summer barbecues or autumn storage crops.

Climate Adaptation

Adjust the default growing days to match your local climate - crops grow faster in warmer regions and slower in cooler areas.

Why This Calculator Is Approximate

This timeline calculator uses generic days-to-maturity data from seed catalogues. Real-world growing times depend on many factors:

Climate & Temperature: Warm weather accelerates growth; cool weather slows it down
Daylight Hours: Many crops are photoperiod-sensitive and grow differently in long vs short days
Frost Dates: Your last spring frost and first autumn frost define your safe growing window
Variety Differences: Early, mid, and late-season varieties have very different maturity times
Soil & Care: Fertility, watering, and plant health all affect growth speed

Leaftide takes these variables into account, from your frost dates to local weather and daylight hours, and gives you planting dates for where you garden.

Transplant vs Direct Sow: Which Method?

Best for Transplanting:

Tomatoes, peppers, chillis, aubergines, courgettes, cucumbers, pumpkins, brassicas (broccoli, cabbage, cauliflower, brussels sprouts), lettuce. These benefit from a head start indoors and transplant well.

Must Direct Sow:

Carrots, parsnips, radishes, beetroot, onions, potatoes. Root vegetables don't transplant well because transplanting damages the taproot. Always sow these directly in their final position.

Can Do Either:

Beans (broad, french, runner), peas, lettuce, chard, kale, spinach, rocket. These can be direct sown for simplicity or started indoors for earlier harvests. Choose based on your space and schedule.

Planning Your Growing Season

A planting timeline works in two directions. You can count backwards from your desired harvest date — subtracting days to maturity, germination time, and any indoor growing period — to find the ideal sowing window. Or you can work forwards from your last frost date, adding those same intervals to see when each crop will be ready to pick. Either way, the goal is the same: matching your sowing dates to the reality of your local climate so nothing gets planted too early or too late.

Key timing concepts

The most important number for any crop is days to maturity, but there's a catch most seed packets don't make obvious — that figure is counted from transplant, not from seed. If you're starting indoors, you need to add germination time (typically 5-14 days depending on the crop and soil temperature) plus the weeks of indoor growing before the seedling is ready to go out. For tomatoes, that indoor period is 6-8 weeks. For lettuce, it's closer to 3-4.

There's also the hardening off period to account for. Seedlings raised indoors under stable conditions need 1-2 weeks of gradual exposure to outdoor temperatures, wind, and direct sun before they can handle life in the garden. Skip this step and even healthy transplants will suffer transplant shock, setting them back by weeks. I build this buffer into every timeline — it's the difference between a schedule that works on paper and one that works in the soil.

Succession planting

One of the simplest ways to extend your harvest is succession planting — sowing the same crop every 2-3 weeks instead of all at once. Instead of 30 lettuces maturing in the same week (and half of them bolting before you can eat them), you get a steady handful every few days from late spring through autumn. This technique works brilliantly for fast-maturing crops like lettuce, radishes, spinach, and beans. It doesn't make sense for crops with a single long growing cycle — tomatoes, peppers, and squash take so long to mature that you'd run out of season before a second sowing could finish.

Indoor vs outdoor sowing

Not every crop benefits from an indoor start. Tomatoes, peppers, aubergines, and chillies genuinely need it — they require warmth to germinate (20-25°C) and a long season that most climates can't provide without a head start. But root vegetables like carrots, parsnips, and beetroot resent being transplanted and should always be sown directly where they'll grow. Beans and peas germinate quickly in warm soil and gain little from indoor sowing unless you're trying to get ahead of slugs in a wet spring. The rule of thumb: if a crop has a taproot or matures in under 60 days, direct sow it.

Your growing season sets the boundaries

Everything above depends on one fundamental constraint: the length of your frost-free growing season. Count the days between your average last spring frost and first autumn frost — that's your window. A generous 180-day season gives you room for long-season crops like butternut squash or sweet potatoes without stress. A tighter 150-day season means you'll need to choose quick-maturing varieties of warm-season crops, or accept that some things simply won't ripen outdoors in your climate. Knowing your number up front saves you from planting something ambitious in May only to watch it get killed by frost in September with green fruit still on the vine.

Frequently asked questions

How do I plan a planting timeline?

Start by identifying your desired harvest date and work backwards, or begin from your last frost date and work forwards. Subtract the days to maturity and germination time from your target harvest date to find your ideal sowing window. A crop timeline calculator automates this by factoring in each crop's specific growth stages.

What is succession planting?

Succession planting means sowing the same crop at regular intervals, typically every 2-3 weeks, to spread your harvest over a longer period. Instead of getting a glut of lettuce all at once, you get a steady supply throughout the growing season. This technique works especially well for fast-maturing crops like salads, radishes, and beans.

When should I start seeds indoors?

Count backwards from your transplant-out date (which is typically after your last frost date) by the number of weeks the seedling needs to develop indoors. Most crops need 4-8 weeks of indoor growing time — for example, tomatoes need about 6-8 weeks while lettuce only needs 3-4 weeks. Starting too early leads to leggy, weak transplants.

How do frost dates affect my planting schedule?

Your last spring frost date is the key anchor for scheduling frost-tender crops like tomatoes, peppers, and courgettes — these must go outdoors only after that date. Frost-hardy crops such as peas, broad beans, and kale can be planted several weeks earlier. The crop timeline calculator accounts for each plant's frost tolerance automatically when building your schedule.

What does days to maturity mean?

Days to maturity is the number of days from transplanting (not from seed) until a crop is ready to harvest. If starting from seed indoors, add 1-2 weeks for germination plus the indoor growing period to get your total timeline.

Does days to maturity start from seed or transplant?

For most crops, days to maturity counts from transplant date — when the seedling goes into the ground. Direct-sown crops like carrots and radishes count from the sowing date since they are not transplanted.

How do I calculate harvest date from planting date?

Add the days to maturity to your planting date. If starting from seed indoors, also add germination time (7-14 days) and the indoor growing period. For example, tomatoes started from seed need about 6-8 weeks indoors plus 60-80 days after transplanting.

How accurate are harvest date calculators?

Harvest date calculators give a useful estimate, but actual harvest timing varies by 1-2 weeks depending on weather, soil conditions, sunlight, and variety. Warmer-than-average seasons shorten the timeline; cool or overcast weather extends it.