We suggest organic Acadia Spinach as a replacement
It is very difficult to find spinach adaptable enough to tolerate hot weather but this variety fits the bill. A quick grower with beautiful spoon-shaped leaves that is both bolt resistant and resistant to downy mildew. We found it to be the best growing spinach in our trials this summer. Tasty full-sized or baby. Harvest the baby leaves to encourage more new growth. The last one to bolt in the heat and remained appetizing. Resistance to downy mildew.

PLANTING
Spinacia oleracea
Germination: 7-14 days
Germination Temperature: Optimum soil temperatures 50-70ºF
Seed Sowing Depth: 1/2" deep
Sowing Indoors: 3-4 weeks before planting out in early to mid-spring. Provide 50-65ºF soil temperature. Sow 2-3 seeds per cell/pot. Sowing into individual biodegradable peat/cow pots reduces root damage when transplanting. Transplant after last frost, 6-12" apart.
Sowing Outdoors: Start in early spring when the soil temperature is over 50ºF. Sow a few seeds every 1-3", thin to 6-12" for full-sized plants. Sow heavy seeded rows, 30 seeds per foot, every 10-14 days for baby greens using the Pinetree spinach mix or larger 1000 seed packet. Sow in mid to late summer for fall harvests.
How much does a packet plant: Small packet= 6-10 feet, large packet = 80-100 feet for mature plants or 20-25 feet for baby greens
Harvest: Starting with baby greens at 3” or the entire plant before it bolts.
Tips: Plant in fertile soil, amended with compost or well-rotted manure, and keep well watered. Sow in the fall and cover with mulch for an early spring crop.