Seed to Harvest Countdown
Not sure when your hydroponic plants will be ready? This free seed to harvest countdown calculator tells you exactly what growth stage your crop is in right now, when to expect your first harvest, and what signs to look for when it is ready to pick.
Enter your crop, whether you started from seed or transplant, and your planting date. The calculator tracks your grow in real time and shows each growth stage with days remaining.
Step 1 of 3 – Choose your crop
What are you growing?
Your harvest countdown
⏳ Growth Stage Timeline
🔍 Harvest Signs
📋 How to use this seed to harvest countdown calculator
- Choose your crop from all 15 common hydroponic crops. Use the category tabs to filter by leafy greens, herbs, fruiting vegetables, or specialty crops.
- Select your starting point so the calculator can use the right timeline. Starting from seed includes germination and seedling stages. Starting from transplant skips straight to the system stages.
- Enter your planting date – the day you put seeds in rockwool or transplanted into your system. You can enter a past date if your grow is already underway.
- Read your countdown and see your current growth stage, estimated harvest date, days remaining, and the signs to look for at harvest time.
❓ Common questions about hydroponic grow times
🥬 What is the fastest crop to grow hydroponically?
Microgreens and wheatgrass are the fastest, reaching harvest in 7 to 14 days from seed. For full-size crops, lettuce is the fastest at 28 to 45 days from seed, followed by arugula at 30 to 40 days and bok choy at 30 to 50 days. Fruiting crops like tomatoes and peppers are the slowest at 100 to 150 days.
🌱 How long does hydroponic lettuce take from seed to harvest?
Hydroponic lettuce typically takes 28 to 45 days from seed to first harvest. From transplant, it is usually 21 to 35 days. Warmer temperatures and 16 hours of light per day push growth toward the faster end.
🍅 How long do hydroponic tomatoes take?
Hydroponic tomatoes take 100 to 130 days from seed to first ripe fruit, or 60 to 90 days from transplant. Cherry tomato varieties are generally faster. Strong light (600 to 900 PPFD) and daily hand-pollination are both required for indoor fruit.
✂️ What does cut-and-come-again mean?
Cut-and-come-again means you harvest outer leaves or stems repeatedly from the same plant rather than pulling the whole plant out. Lettuce, arugula, basil, mint, chives, and cilantro all regrow after cutting. Always cut above a leaf node and leave at least 4 to 5 leaves on the plant.
📅 Why is my plant taking longer than the countdown says?
Insufficient light is the most common reason, followed by water temperature below 18 degrees C, EC too low (underfeeding), or pH outside 5.5 to 6.5 causing nutrient lockout. If your plant is behind schedule, check light hours and EC first. Use our grow light calculator and pH calculator to dial in your setup.
🧫 Do I need rockwool or rapid rooter plugs to germinate?
You do not need either for simple Kratky lettuce – you can germinate directly in the Kratky lid with a small amount of growing medium. For seeds that need consistent moisture (basil, tomatoes, peppers), rockwool cubes at $8.99 for 100 plugs or rapid rooter plugs at $17.99 for 50 inside a humidity dome give much better germination rates.
💧 Should I use a humidity dome for hydroponic germination?
Yes for most crops, especially in dry rooms. A humidity dome keeps moisture around the seeds during the critical first 3 to 7 days. The AC Infinity dome at $74.99 includes a built-in LED for the germination phase. Once seeds sprout and you see root tips, remove the dome to prevent damping off.
🧪 When should I start measuring EC and pH?
Start checking pH from day one since it affects germination. Target pH 5.8 to 6.2. Add nutrients at 25 percent strength once the first true leaves appear. Increase to full strength once the plant is established. A basic pH and EC meter set starts at $16.99 on Amazon.