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Garden Planning, Succession & Crop RotationSeed Starting Calendar by Crop
Starting seed indoors is a counting exercise. Pick the date you want to transplant, then work backward by the weeks each crop needs.
Key points
- Choose the transplant date first, then count back the weeks each crop needs.
- Not every crop likes indoor starting, so check each one.
- Light is the main limit for strong seedlings.
- Harden off for a week or two before transplanting.
How do you work out a seed starting date?
Begin with the date you plan to move seedlings into the garden. For cool-season crops, that is often a few weeks before your average last spring frost. For warm-season crops, it is after the last frost, when nights are mild and soil has warmed. Then subtract the weeks each crop needs, which are given on seed packets and in extension guides.
For example, if a crop needs about six weeks from sowing to transplant and you plan to set it out in early May, you would sow in mid to late March. This is an illustration of the counting method, so use your own frost dates and the packet.
Many extension offices publish a chart with weeks before the last frost for each crop, which can save you from doing the sums yourself.
Which crops benefit from indoor starting?
Crops with a long season or a slow start, such as tomatoes, peppers, eggplant and onions, usually benefit. Many brassicas are also started indoors for early or fall crops. Others, such as beans, peas, carrots, radishes and most cucurbits, are typically sown directly or started only briefly indoors, because they dislike root disturbance.
Check your seed packet or extension guide for each crop, since needs differ.
Local conditions will decide the final dates, so ask your extension office for a seed starting chart written for your county. Seed packets from different companies can vary in their advice, and the weeks given are an average under typical conditions. If your seedlings are too small at transplant, start a week earlier next year, and if they are root-bound, start a week later.
- Often started indoors: tomato, pepper, eggplant, onion, many brassicas
- Often direct sown: beans, peas, carrots, radishes, beets
- Short indoor starts only: cucumbers, squash, melons, since roots dislike disturbance
What do seedlings need?
Seedlings need clean containers, fresh seed-starting mix, steady moisture, warmth for germination and plenty of light after emergence. Light is the main limit: a sunny window is often not enough, which leads to tall, weak seedlings. Lights placed close above the plants help.
Thin seedlings to one per cell, and water from below or gently from above to avoid damping off, a disease that kills seedlings at the soil line. Clean tools and containers reduce the risk.
Fresh, clean seed-starting mix drains well and is free of many of the pathogens found in garden soil, so garden soil is rarely a good choice for trays.
How do you stagger sowings?
Sowing all of one crop at once means all seedlings are ready together. If you want a longer harvest or you have limited space, sow in batches a week or two apart. This is also a good way to hedge against late frost, giving you plants of different sizes.
Keep a small spare supply in case of losses, since some seedlings fail.
When should you pot up and harden off?
Seedlings that outgrow their cells may need transplanting into larger pots, handled by the leaves, not the stem. Begin hardening off about a week or two before transplanting, with short outdoor periods in a sheltered, shaded spot, building up to full sun and wind.
Skip hardening off and plants may suffer from sunscald or wind damage, so plan the time into your calendar. Pot up gently, holding seedlings by a leaf and not by the stem, since a crushed stem cannot recover while a lost leaf can regrow. Use fresh mix in the larger pot and water it in, then keep the seedlings out of strong sun for a day or two while the roots settle.
How do you test seed and record results?
Test older seed with a damp paper towel before you sow. Record the sowing date, germination date, transplant date and the results for each crop. Over time, you will see whether you started too early or too late.
Adjust your dates by a week at a time, not by large jumps, and trust your own records alongside extension guidance.
What are the most common errors?
Starting too early is the most common, leaving oversized, stressed seedlings. Others are weak light, overwatering and ignoring hardening off.
If a crop fails, note what happened and try again with one change.
Keep labels with each tray, since seedlings look alike at the start, and note variety names for next year's records. Seedlings kept too warm and too dim stretch quickly. Give them the coolest spot that still suits the crop once they have emerged, and keep lights close to the leaves.
Sources and further reading
Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.