I want to grow later into fall and earlier in spring
Order of operations matters here: row cover is nearly free and buys weeks, a cold frame buys more, and the big structures only pay off if you've already used the cheap tricks.
What actually works
Earth-sheltered greenhouse. The physics is real; drainage decides whether you built a greenhouse or a swimming pool.
$500–5,000 and a lot of dirt5–15°F of overnight lift for about 100 W of fan. Must be installed before the floor goes in.
$1,000–4,000, mostly at construction time2–4°F of protection for pennies, which in October is often two more weeks. The highest return per dollar in season extension.
36°F on the porch is 32°F on your tomatoes. A sensor at plant height, not on the wall, is what actually wakes you in time.
Run the numbers
- Planting & transplant dates → — free calculator, works offline.
- Last date you can still plant it → — free calculator, works offline.
Also searched as
season extension · grow in winter · greenhouse winter growing · cold frame · frost protection · longer growing season · underground greenhouse