In most of the country, tomato season is over. In Arizona's low desert, the countdown is just starting. Native Seeds/SEARCH in Tucson recommends sowing tomato seeds indoors about 6 to 8 weeks before the last frost, which in the low desert means early December to mid-January, then moving seedlings outside from about mid-February to mid-March, once frost danger has passed and the soil has warmed. (Native Seeds/SEARCH: Starting Tomato Seeds in the Desert)
That gives homeschool families a few weeks of runway. Instead of planting your whole crop and hoping, use November for a practice round: a small germination experiment that teaches kids exactly what tomato seeds need, so December's real planting goes smoothly.
Southern Arizona garden educators are thinking ahead too. This Saturday, Nov. 7, Sprouts House in Tucson is hosting a School Garden Masterclass on what to plant in the desert and when. (Green Living Magazine, November 2026 events)
What your kids will learn
A tomato seed is small, but it holds a whole plant waiting for the right signal. Finding that signal is real science.
Grades K–5
- What seeds need to sprout: water, warmth and air
- How to spot the root, the shoot and the first seed leaves (cotyledons)
- Comparing how different tomato varieties sprout
- Recording observations with drawings and simple measurements
Grades 6–12
- The stages of germination and early seedling development
- Why temperature matters: Native Seeds/SEARCH notes tomato seeds germinate best around 75°F
- Heirloom (open-pollinated) varieties and how traits are inherited
- Collecting, graphing and interpreting germination data, and why too little light makes seedlings tall and weak
This week's activity: the warm spot vs. cool spot seed race
This test answers a question every desert gardener cares about: how much does temperature change germination? Any tomato seeds will work, including seeds saved from a store-bought tomato (rinse and dry them first).
You'll need: tomato seeds, two paper towels, two zip-top bags, a marker, a kitchen thermometer if you have one, and a notebook.
- Ask a question. "Will tomato seeds sprout faster in a warm spot or a cool spot?" Have everyone write a prediction.
- Prepare two bags. Dampen each paper towel until it's moist but not dripping. Place 10 seeds on each towel, fold it over and slide it into a bag. Label one bag "warm" and one "cool."
- Keep it fair. Same number of seeds, same towels, same water. The only thing that changes is temperature. That's your independent variable.
- Pick your spots. Put the warm bag somewhere around 75°F (a warm shelf away from direct sun works). Put the cool bag somewhere noticeably cooler, like a chilly room or a cool windowsill. If you have a thermometer, record each spot's temperature.
- Check every day. Count how many seeds have a visible root and record it on a chart. Keep the towels damp.
- Graph the race. After 10 days, younger kids can make a bar chart of total sprouts. Older kids can graph sprouts per day for each bag and calculate a germination rate.
- Plan December. Use what you learned to choose the best spot in your house for your real seed starting next month.
Want it all in one box? Our Heirloom Tomato Seed Germination Science Kit includes 20 heirloom tomato seeds in assorted varieties, absorbent germination paper, and grade-level curriculum and observation worksheets (emailed after purchase), including a variety comparison chart for days to sprout and root length. Tomato seeds typically sprout in 3 to 10 days, and once roots reach about half an inch, kids transplant the seedlings into soil to keep the study going, right on schedule for an Arizona spring garden.
Join the growing community
Every kit includes an invitation to Aardvark's Seed Planting For Little Hands, our private support group for students and families using our kits. Post your seed race graph, show off your first true leaves, or ask for help when seedlings get leggy. Young growers in Arizona, Arkansas and West Virginia are all growing at once, and it's eye-opening for kids to see how a desert winter compares with an Appalachian or Ozark one.
Get your tomato seed lab ready
- Heirloom Tomato Seed Germination Science Kit – Plant Biology Curriculum & Worksheets: $25, with Grades K–5 or 6–12 curriculum.
- Native Seeds/SEARCH points out that a sunny window usually isn't enough light for strong seedlings. If you want a dedicated indoor setup, the LED Grow Light Plant Stand Science Kit ($168.99) gives you two lighted shelves with full-spectrum LED bars, plus curriculum and worksheets. Assembly is required, and trays are sold separately.
