Complete Harvest Date Calculator User Guide

What It Does

The Harvest Date Calculator helps you determine when your vegetables will be ready for harvest based on when you planted them and their days to maturity (DTM). This tool takes the guesswork out of garden planning and helps you know exactly when to expect fresh produce from your garden.

How to Use the Calculator

📅 Calculator Tab

Step 1: Select Your Vegetable

Choose from 27 common vegetables in the dropdown menu:

Tomatoes (4 varieties):

• Standard Tomatoes: 70-90 days
• Cherry Tomatoes: 50-70 days
• Early Girl: 50-60 days (fastest)
• Roma: 70-80 days (determinate)

Other Popular Crops:

• Peppers (Sweet/Hot)
• Beans, Beets, Broccoli
• Brussels Sprouts, Cabbage, Carrots
• Cauliflower, Corn, Cucumbers
• Eggplant, Lettuce, Onions
• Peas, Potatoes, Pumpkins
• Radishes, Spinach, Squash
• Watermelon

When you select a vegetable, the Days to Maturity field auto-fills with the average DTM for that crop.

Step 2: Verify Days to Maturity

• The calculator auto-fills the DTM based on your vegetable selection
• Check your seed packet for the exact DTM for your specific variety
• Override the value if your seed packet shows a different number
• Different varieties have different maturity times (e.g., Early Girl tomatoes mature faster than Beefsteak)

Important: DTM on seed packets is your most reliable source!

Step 3: Enter Planting Date

Select the date when you:

• Planted seeds directly in the garden, OR
• Transplanted seedlings into the ground

Note: If you started seeds indoors and are transplanting, use the transplant date (not the indoor seeding date).

Step 4: Select Growing Zone (Optional)

Choose your USDA Hardiness Zone for climate adjustment:

Why zones matter: Cool climates slow plant growth; warm climates speed it up.

Step 5: Calculate

Click “Calculate Harvest Date” to see your results:

Results Display:

• Planting Date: When you planted
• Days to Maturity: Adjusted for your zone
• Expected Harvest: Most likely harvest date
• Complete Harvest Window: Early, average, and late harvest dates
• Harvest Tips: Specific advice for your crop

Example Result:

textTomatoes (Standard) Harvest Timeline
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Planting Date: May 15
Days to Maturity: 80 days
Expected Harvest: August 3

Complete Harvest Window:
• Early Harvest: July 24 (70 days)
• Average Harvest: August 3 (80 days)  
• Late Harvest: August 13 (90 days)

📖 Growing Guide Tab

Comprehensive reference information covering:

Understanding Days to Maturity

• What DTM means
• How to find DTM for your plants
• Why DTM varies by variety
• Environmental factors affecting maturity

Climate Zone Adjustments

• How temperature affects growth
• Zone-specific adjustments (+/- days)
• When to use zone modifiers

Types of Harvest

Single Harvest Crops:

• Carrots, radishes, potatoes
• Determinate tomatoes (Roma)
• Pumpkins, winter squash
• Harvest once when mature

Continuous Harvest Crops:

• Indeterminate tomatoes
• Lettuce, cucumbers, beans
• Peppers, herbs
• Produces all season after first maturity

Tips for Accurate Predictions

• Always check seed packets
• Keep a garden journal
• Track actual harvest dates
• Note weather conditions
• Learn your microclimate

Information Sources

Where to find reliable DTM data:

• Seed packets (most accurate)
• Seedling cards from nurseries
• Previous growing experience
• University extension websites
• Farmer’s Almanac

📊 DTM Chart Tab

Quick reference chart with average days to maturity for common vegetables, organized by plant family:

Categories:

• Nightshades: Tomatoes, peppers, eggplant
• Cucurbits: Cucumbers, squash, melons, pumpkins
• Leafy Greens: Lettuce, spinach, kale, chard
• Root Vegetables: Carrots, beets, radishes, potatoes
• Brassicas: Broccoli, cabbage, cauliflower, Brussels sprouts
• Legumes & Others: Beans, peas, corn, herbs

Each entry shows:

• Crop name
• Average DTM
• Min-Max range

Understanding Days to Maturity (DTM)

What is DTM?

Days to Maturity is the time from planting until first harvest when your vegetable is ready to pick and eat. It represents the number of days between:

• Planting seed or transplant in the ground
• First edible harvest

Key Factors Affecting DTM:

1. Variety Differences

Different varieties of the same vegetable mature at different rates:

• Early Girl tomatoes: 50-60 days (fast)
• Standard tomatoes: 70-90 days (medium)
• Beefsteak tomatoes: 85-100 days (slow)

2. Temperature

• Cool weather: Adds 5-10 days (slower growth)
• Optimal weather: Matches seed packet DTM
• Hot weather: Subtracts 5-10 days (faster growth)

3. Starting Method

• Direct seeding: Use full DTM from seed packet
• Transplants: DTM counts from transplant date (already grew 4-6 weeks indoors)

4. Growing Conditions

• Water availability: Consistent moisture = on-time maturity
• Soil quality: Rich soil = faster growth
• Sunlight: Full sun = faster maturity
• Spacing: Proper spacing = healthy growth

Harvest Windows Explained

Why Three Dates?

The calculator provides three harvest dates because actual harvest timing varies:

Early Harvest (Minimum DTM):

• Best-case scenario
• Ideal weather and conditions
• Warmest climates
• First possible harvest date

Average Harvest (Standard DTM):

• Most likely harvest date
• Based on seed packet DTM
• Use this for planning
• Most reliable estimate

Late Harvest (Maximum DTM):

• Worst-case scenario
• Cool weather or poor conditions
• Conservative estimate
• Latest expected harvest

Typical Range: ±10-15 days around average

Growing Zone Adjustments

How It Works:

The calculator adds or subtracts days based on your USDA Hardiness Zone because temperature significantly affects plant growth rates.

Zone Adjustment Table:

Example:

• Tomatoes: 80 days DTM (standard)
• Zone 4: 85 days (cooler = slower growth)
• Zone 10: 77 days (warmer = faster growth)

Practical Examples

Example 1: Early Girl Tomatoes

textVegetable: Tomatoes (Early Girl)
DTM: 55 days
Planting Date: May 20, 2025
Zone: 6-8 (Moderate)

Results:
• Early Harvest: July 9 (50 days)
• Average Harvest: July 14 (55 days) ← Plan for this
• Late Harvest: July 24 (60 days)

Example 2: Radishes (Quick Crop)

textVegetable: Radishes
DTM: 30 days
Planting Date: April 1, 2025
Zone: 5 (Cool)

Results:
• Early Harvest: April 29 (28 days)
• Average Harvest: May 4 (33 days) ← With zone adjustment
• Late Harvest: May 14 (43 days)

Example 3: Pumpkins (Long Season)

textVegetable: Pumpkins
DTM: 100 days
Planting Date: June 1, 2025
Zone: 7 (Moderate)

Results:
• Early Harvest: August 25 (85 days)
• Average Harvest: September 9 (100 days)
• Late Harvest: September 29 (120 days)

Pro Tips for Accuracy

1. Check Your Seed Packet

✅ Always use the DTM from your specific seed packet

• Different brands and varieties vary
• Seed packets have the most accurate data for that variety
• Override the calculator’s auto-fill if different

2. Account for Starting Method

• From seed: Use full DTM
• From transplant: DTM counts from transplant date
• Seedlings you bought: Ask nursery or check plant tag

3. Keep a Garden Journal

Track actual harvest dates each year:

textExample Entry:
- Crop: Early Girl Tomatoes
- Planted: May 15, 2024
- First Harvest: July 10, 2024
- Actual DTM: 56 days
- Notes: Hot summer, dry conditions

4. Understand Your Microclimate

Your specific garden may be:

• Warmer: South-facing wall, heat sink → subtract days
• Cooler: Shaded, north-facing, low spot → add days
• Windy: Exposed location → add 3-5 days

5. Plan for Succession Planting

For continuous harvest:

• Lettuce: Plant every 2 weeks (50 days each)
• Radishes: Plant every 2-3 weeks (30 days each)
• Beans: Plant every 3 weeks (55 days each)

Harvest Timing by Crop Type

Quick Crops (Under 40 Days)

Perfect for succession planting:

• Radishes: 25-30 days
• Arugula: 30-40 days
• Baby lettuce: 30-45 days

Strategy: Plant every 2 weeks for continuous harvest!

Fast Crops (40-60 Days)

Great for beginners:

• Lettuce: 45-60 days
• Spinach: 40-50 days
• Beans: 45-55 days
• Summer squash: 40-50 days

Medium Crops (60-85 Days)

Standard garden vegetables:

• Cucumbers: 50-65 days
• Tomatoes (early): 50-60 days
• Peppers: 60-75 days
• Broccoli: 55-65 days

Long Season Crops (85+ Days)

Plan ahead for these:

• Standard tomatoes: 75-90 days
• Eggplant: 80-90 days
• Brussels sprouts: 90-100 days
• Pumpkins: 100-120 days
• Winter squash: 100-120 days
• Potatoes: 90-120 days

Common Questions

Q: Do I count from seed or transplant?

A: The calculator counts from the date seeds or transplants go into the ground. If you started seeds indoors 6 weeks ago and transplanted yesterday, use yesterday’s date.

Q: Why does my seed packet say “65-75 days”?

A: Ranges account for variety and conditions. Use the average (70 days) in the calculator. Your actual harvest will fall within this range.

Q: Can I harvest earlier than the DTM?

A: Some crops can be harvested early:

• Lettuce: “Baby” greens at 25-30 days
• Carrots: Small “baby carrots” at 50 days
• Potatoes: “New potatoes” 60-70 days
  But full-size harvest requires full DTM.

Q: What if I miss the harvest window?

A: Many crops continue producing or can stay in the ground:

• Tomatoes, peppers, cucumbers: Keep producing if harvested regularly
• Root vegetables: Can stay in ground 2-4 weeks past maturity
• Leafy greens: May bolt in heat; harvest immediately

Q: Do perennials have DTM?

A: No, DTM applies to annual vegetables. Perennials (asparagus, rhubarb, artichokes) are harvested based on maturity year (usually year 2-3).

When to Harvest Different Vegetables

Harvest Timing Indicators:

Tomatoes:

• Full color development
• Slight give when squeezed
• Glossy appearance
• Pick before first frost

Peppers:

• Green stage: Any size after flowers
• Colored stage: Wait for full color change
• Firm and glossy

Cucumbers:

• 6-8 inches (slicing)
• 3-5 inches (pickling)
• Pick daily for continuous production

Lettuce:

• Outer leaves: Anytime after 4 inches
• Full head: Before bolting (flower stalk)

Carrots:

• When shoulders visible at soil line
• Orange color at top
• DTM reached

Radishes:

• When bulb diameter reaches 1 inch
• Before hot weather (become woody)

Troubleshooting

Harvest is Later Than Expected:

Possible Causes:

• Cool weather slowed growth
• Insufficient water or nutrients
• Too much shade
• Plants spaced too close
• Wrong variety DTM used

Solutions:

• Be patient – add 1-2 weeks
• Improve growing conditions
• Check seed packet DTM again

Harvest is Earlier Than Expected:

Possible Causes:

• Hot weather accelerated growth
• Optimal growing conditions
• Used transplant DTM for direct-seeded plants

Solutions:

• Check plants daily as DTM approaches
• Harvest when ready, not by calendar

Plants Not Producing:

Possible Causes:

• Too early (haven’t reached DTM yet)
• Lack of pollination
• Environmental stress
• Disease or pest damage

Solutions:

• Wait until DTM is reached
• Hand-pollinate if needed
• Address pest/disease issues

Seasonal Planning

Spring Planting:

textLast Frost: May 15
Plan Backwards:

Tomatoes (80 days) → Harvest: Aug 3
- Start indoors: March 1 (10 weeks before planting)
- Transplant: May 20 (after frost)

Lettuce (50 days) → Harvest: June 15  
- Direct sow: April 25 (before frost OK)

Fall Planting:

textFirst Frost: October 10
Plan Backwards:

Broccoli (60 days) → Harvest: Oct 5
- Plant: August 6 (60 days before frost)
- Start indoors: July 15 (for transplanting)

Spinach (45 days) → Harvest: Sept 25
- Direct sow: August 11

Advanced Features

Succession Planting Calculator:

Use the calculator multiple times for staggered plantings:

Example: Continuous Lettuce

textPlanting 1: April 15 → Harvest: June 4
Planting 2: May 1 → Harvest: June 20  
Planting 3: May 15 → Harvest: July 4
Planting 4: June 1 → Harvest: July 21

Intercropping Timeline:

Calculate harvest dates for companion crops:

Example: Three Sisters

textCorn (85 days): June 1 → Aug 25
Beans (55 days): June 15 → Aug 9
Squash (100 days): June 15 → Sept 23

Best Practices

✅ Always check seed packets for variety-specific DTM
✅ Record actual harvest dates in a garden journal
✅ Plan for the average date, not early or late
✅ Add 1-2 weeks buffer for first-time crops
✅ Check plants daily as harvest window approaches
✅ Harvest in the morning for best flavor and storage
✅ Pick regularly to encourage more production

Angelina Everly

Angelina Everly leads the editorial desk at Live Green Gardens, blending practical plant care, hands-on product testing, and approachable outdoor styling. She focuses on step-by-step how-tos, buyer’s guides, and small-space makeovers that work in real life and real budgets. When she’s not comparing pruning shears or setting up a drip kit, you’ll find her creating cozy corners with planters, solar lights, and pollinator-friendly picks—always with clear pros/cons and safety notes so you can buy once and garden happy.