Most indoor seed starting begins just weeks before last frost in spring. But some plants like the vegetable cultivars listed here are slow-growing and need a much longer jump start. Started indoors in winter and planted out in late spring, they’ll have time to mature before fall.
If you are interested in outdoor sowing, I have two winter sowing methods here.
Slow-Growing Vegetables to Start Early
Indoor seed starting is a simple way to extend the growing season, allowing us to grow a much wider variety of plants than we could with direct outdoor sowing alone.
Seed packets typically recommend a specific timeline (number of weeks before last frost) for starting seeds indoors to get plants established for transplanting outdoors in spring.
What surprises gardeners is not all cultivars of the same species have the same time requirements.
- For example, the days to maturity for Early Girl tomatoes are just 50 days while Brandywine tomatoes require twice as long—100 days.
- Aspabroc broccolini takes 56 days while Santee broccoli needs up to 115 days.
Those are big differences for the same vegetables!
This is why it’s smart to read your seed packets, flag the slow-growers, and start them much earlier in late winter.
Be sure you have room under your grow lights not only for trays of seedlings but for moving the plants into larger pots (3-6 inches in diameter) as they grow.
I use this system to sow batches every two weeks from winter onward to make sure everything starts on time.
It’s helpful to know your average last frost date and typical number of frost-free days from spring to fall to get started. I’ve listed a calculator for this and other helpful items in the Resources section.
Slow-Growing Vegetables to Start Extra Early
Timing Examples
This chart allows approximately 12 weeks or 90 days of indoor growing before last frost.
- Last frost in March: start these seeds in December
- Last frost in April: start these seeds in January
- Last frost in May: start these seeds in February
- Last frost in June: start these seeds in March
I’ve provided some these examples by browsing favorite seed catalogs. As mentioned, check your seed packets for specific growing instructions.
Broccoli
- Early Broccoli: Early broccolis are faster growing but often do best in cooler weather. If you want to plant them out in spring, you’ll want to sow seeds indoors in winter.
- Santee Broccoli (80-115 days)
- Calabrese Broccoli (60-90 days)
- Purple Sprouting Broccoli (90-100 days)
- Romanesco Broccoli (75-100)
Celeriac
- Giant Prague (110-120 days)
- Brilliant (105-115 days)
- Monarch (110 days)
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Celery
- Tall Utah (90-100 days)
- Golden Self-Blanching (90-120 days)
- Tango Hybrid (85-90 days)
Eggplant
- Black Beauty (74 days)
Leeks
- Giant Musselburgh (105 days)
- Otina (120 days)
- Splendid (95-105 days)
Onion
Sweet onions in particular can be slow-growers. It takes a long time to grow those large bulbs.
- Walla Walla (125 days)
- Sweet Spanish (110 days)
- Trident (115 days)
Peppers
- Chili peppers (Capsicum chinense) including Habanero types require 90-120 days to mature after transplanting.
- Anaheim (75-80 days)
- California Wonder (70 days)
Tomatoes
- Mortgage Lifter (85 days)
- Amana Orange (80 days)
- Cherokee Purple (80 days)
- Brandywine (90-100 days)
- Chef’s Choice Orange (75 days)
Resources
What is Days to Maturity?
Days to maturity or days to harvest is the average number of days a plant takes to reach maturity. Depending on the type of plant, this could be when a vegetable is ready to harvest or a flowering plant is in bloom. It’s a ballpark number to assist with planning.
While there’s no universal consensus, I use the following for my calculations.
- For seeds sown directly outdoors, counting begins after germination when the first true leaves appear.
- If seeds are started indoors, counting begins when they are transplanted outdoors.
Again, it’s just a ballpark number. Factors like weather and other growing conditions can throw things off. While plants can only grow so fast in optimum conditions, things like excessive heat or drought can delay or stop plants from maturing. Plus, growth will slow as we head into fall as temperatures drop and hours of daylight decreases.
Knowing the estimated days to maturity is most helpful for fruiting plants like tomato, zucchini, peas, or watermelon that need time to flower and fruit in the growing season.
It’s not really an issue for vegetables grown for the solely for their stems and leaves since they can be harvested at any time.
Mail Order Seeds
- SeedsNow | Botanical Interests United States
- West Coast Seeds Canada
Find Your Frost Dates & Hardiness Zone
Plant Hardiness Zones | United States | Canada
These are listed on seed packets and plant tags to guide your choices.
Average Frost Dates | Use this calculator at Almanac.com. Enter your city and state or province to find your first and last frost dates and number of frost-free days.
Ecoregion | Learn about local native plants, animal species, and environmental conditions to make garden choices that benefit your ecosystem.
Learn More: Understanding Frosts & Freezing For Gardeners
Ebook
Seed Starting for Beginners
Sow Inside Grow Outside
by Melissa J. Will
NEW EDITION | Everything you need to get started with indoor seed starting for indoor and outdoor plants. Grow what you want—any time of year!
About This Ebook | Visit Ebook Shop
This ebook is a digital file (PDF format) you save to your device. It is not a physical product.
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~Melissa the Empress of Dirt ♛