How do raised beds extend the gardening season?
Written by
Michael Sullivan
Reviewed by
Prof. Charles Hartman, Ph.D.Raised beds produce unique microclimates and lengthen your gardening season. An artificial microclimate holds advantages through the incorporated design features. Raised beds help overcome temperature fluctuations for earlier spring planting and later fall harvests. Using these methods for season extension, I have fresh greens to harvest 10 months of the year. The key is how the bed manipulates the air temperature and soil warmth.
Accelerated spring soil warming enables you to plant 2 to 3 weeks early. Since raised beds drain excess moisture from the soil, the soil warms quickly than that in the ground beds. Dark materials such as black plastic absorb more solar heat. My lettuce sowings in raised beds come to maturity weeks before those in the ground, experiencing a great acceleration in spring growth.
Cold Frame Integration
- Attach hinged glass/plastic lids to bed frames
- Maintain temperatures 10-20°F (5-11°C) above outdoor levels
- Harvest spinach and kale through winter months
Row Cover Systems
- Use fabric weights to secure covers directly to bed edges
- Choose thickness based on temperature needs: 2°F-8°F (1°C-4°C) gain
- Protect seedlings from late frosts and early snows
Thermal Mass Utilization
- Place water jugs along bed edges to absorb daytime heat
- Use dark stones to radiate warmth overnight
- Thermal mass prevents sudden temperature drops
Better frost drainage protects the plants during the changeable temperatures. The high beds prevent the water at the roots from freezing in cold snaps. The broccoli survived the sudden frosts of October while those in the ground died. This feature of good drainage greatly prolongs the fall harvest season without requiring any extra protection.
The windbreak feature protects small seedlings. The side of the bed prevents chilling winds and drying of the soil. Place beds at an angle to the prevailing wind to maximize their effectiveness. My pepper starts 30% faster with this windbreak than it does in exposed areas.
Combine methods for the longest extension. I use row covers on cold frames, gaining 20°F (11°C) protection from frost. This has enabled the production of fresh arugula in winter temperatures as low as -10°F (-23°C). Experiment with layered systems to fit your climatic limitations.
Read the full article: 10 Key Benefits of Raised Beds
