Potatoes are a cool weather crop that can be planted in spring once soil reaches the proper temperature. But how late in the season can you successfully plant potatoes before summertime heat arrives? Knowing your climate, selecting the right varieties, and using season extension techniques can extend the potato planting time.
Recommended Planting Dates By Zone
Potatoes prefer cool soil temperatures for optimal growth. Potatoes require cool soil between 50-70°F for tuber development. Here are the recommended potato planting times based on climate zones:
Northern Zones (USDA Zones 2-5)
Plant early season varieties from March 15th – May 15th
Midseason varieties from April 1st – June 1st
Late season varieties from April 15th – June 15th
Mid-Range Zones (Zones 6-8)
Early varieties: February 15th – March 30th
Midseason: March 1st – April 15th
Late: March 15th – April 30th
Southern Zones (Zones 9-11)
Early season: January 15th – February 28th
Midseason: February 1st – March 15th
Late: February 15th – March 31st
Avoid planting potatoes in the summer when temperatures exceed 80-85°F.
Determining Last Possible Planting Date
To calculate the deadline for planting:
Look at the average date summer temperatures above 90°F arrive in your area.
Check the maturity days for your chosen potato variety – early types mature in 60-80 days, midseason 80-100 days, late 100+ days.
Count back from the first 90°F date the number of days your variety needs to reach maturity.
Add 2 more weeks to that date to determine the final planting date to avoid heat stress.
Choosing Late Planting Varieties
When planting later, choose short season potatoes ideal for warmer conditions:
Early – French Fingerling, Caribe, Norland, Irish Cobbler
Midseason – Viking, Dark Red Norland, Yukon Gold, Purple Majesty
Late – Kennebec, Red Pontiac, Chieftain
Avoid long season varieties like Russet Burbanks when planting past midspring.
Using Season Extension Methods
Use season extending techniques to push late plantings:
Start tubers indoors for 4-6 weeks before planting out.
Use floating row covers or low plastic tunnels to retain warmth and block wind.
Mulch heavily around plants to maintain cool, moist soil as temperatures climb.
Use raised beds which warm faster than garden rows.
Provide consistent watering to compensate for increased heat and evaporation.
Risks and Precautions for Late Planting
Be aware of potential issues with late plantings:
- Monitor for early blight, Colorado potato beetles and other pests that thrive in warmer conditions.
- Hill soil deeply around stems to protect developing tubers from heat and light.
- Control weeds rigorously to reduce competition for soil moisture.
- Accept smaller yields or tubers that don’t size up fully before plants shut down.
- With extra diligence, late plantings can still succeed but may not equal a full early spring crop.
Key Tips for Late Potato Planting
- Determine the final planting date in your climate based on days to maturity
- Stick to short season, heat tolerant varieties only
- Use season extending methods like indoor starts, floating row covers, etc.
- Hill deeply and maintain consistent moisture as temperatures climb
- Control pests and diseases aggressively in warmer conditions
- Monitor plants closely and adjust practices as needed
With the right planning and adjustments, potatoes can be planted later than typically recommended in some regions.
Conclusion
Pay close attention to seasonal variations in your specific area. Choosing short season varieties suited to warmer weather, taking steps to maintain cool soil temperatures, and providing sufficient water. By planting potatoes at the appropriate time and providing them with optimal growing conditions, you can increase your chances of a successful harvest and enjoy a bountiful supply of fresh, homegrown potatoes.