A tray of tomato seedlings under a bright window is one of the first signs of spring in a New York yard, long before the garden soil is ready for anything. The seeds go into trays in March or April, and the plants move outside once frost is behind you.
When Should You Start Tomato Seeds in New York?
Start tomato seeds indoors in March or April, with mid-March to mid-April giving seedlings about six to eight weeks to grow before they go outside. That head start produces sturdy transplants that are ready when the garden is.
The planting date is what sets the sowing date. Tomatoes go out in May or June, once the danger of frost has passed and the soil has warmed to about 60°F.
| Step | When in New York | Why |
|---|---|---|
| Sow seeds indoors | March to April, mid-March to mid-April | Gives seedlings six to eight weeks to grow before planting out |
| Harden off | The one to two weeks before planting | Lets tender seedlings adjust to sun, wind and cooler air |
| Plant outside | May to June, late May to early June | Frost danger has passed and the soil has warmed to about 60°F |
For New York City, the last spring frost usually falls between March 23 and April 3. Upstate and the Adirondacks frost later in spring, so gardeners there lean toward the later part of each window. Potting seedlings into larger containers fits between sowing and hardening off, whenever the young plants crowd their cells.
New York — the year and the numbers
- State
- New York
- USDA zones
- 3b-7b
- Last spring frost
- March 23 to April 3
- First fall frost
- November 14 to November 27
- Annual rain
- 50 in
- Lawn zone
- cool-season
- Source
- NOAA NCEI U.S. Climate Normals 1991-2020, 32F freeze probabilities · New York City
How to Start Tomatoes from Seed
Seed starting is simple work, and a few habits make the difference between stocky plants and spindly ones.
- In mid-March to mid-April, fill clean trays with fresh seed-starting mix, moisten it, and sow the seeds shallowly. Warm mix helps seeds germinate, so a spot near a heat source suits the trays until sprouts appear.
- As soon as seedlings emerge, move them into the brightest light you have. A sunny south window can work, and a grow light placed close above the leaves keeps stems short and strong.
- While the seedlings grow, water regularly and keep the mix evenly damp, never soggy. Water from below or with a gentle stream so the tiny stems stay undisturbed.
- When seedlings crowd their cells and grow true leaves, pot them into larger containers. Setting them a little deeper than before gives the stems more chance to root.
- In the one to two weeks before planting, set the plants outdoors for a little longer each day. Hardening off toughens the leaves so they do not scorch or wilt on planting day.
- In late May to early June, once frost danger is gone and the soil has warmed, set the plants in the garden.
Pick varieties with disease resistance in mind. Cornell University maintains a list of disease-resistant tomato varieties, and Neptune, an early-season determinate, is one New York gardeners can look for.
What Happens If You Start Tomato Seeds Too Early
Seeds sown too early produce plants that outgrow their trays long before the garden is safe. They turn tall and weak, with thin stems stretching toward the light and roots circling a small pot.
Those plants have nowhere to go, because tomatoes cannot be planted until frost danger has passed. Moving them into bigger pots buys some time, but crowded, leggy seedlings often stall after transplanting.
Sowing in March or April avoids the problem. If a spring turns out colder than usual, hold the plants indoors a little longer rather than rushing them into chilly soil, where growth stops.
Where to Get Seed-Starting Advice in New York
Local help can fine-tune these dates for your corner of the state, from the city to the Hudson Valley to the North Country. Cornell Cooperative Extension has an office in every county, staffed by people who know your local conditions.
- Visit Cornell Cooperative Extension in late winter to find your county office and its seed-starting guidance.
- Ask your county office about frost timing and disease-resistant varieties before you order seed in early spring.
Common Questions
Can You Start Tomato Seeds Indoors Without a Grow Light?
A bright south-facing window can work, though seedlings often lean and stretch when light is weak. A grow light placed close above the plants gives sturdier stems. Turn trays regularly if you rely on a window.
When Can You Plant Tomatoes Outside in New York?
Plant in May or June, once the danger of frost has passed and the soil has warmed. Upstate gardeners often wait for late May to early June.
Do Tomatoes Need Hardening Off?
Yes. Seedlings raised indoors have soft leaves that scorch in strong sun and wind. A gradual introduction to the outdoors toughens them before they go into the garden.