When to Plant Radishes in Simi Valley, CA
Published: April 24, 2026
Radish Planting Dates for Simi Valley, CA
| Start seeds indoors | Year-round |
| Last frost (average) | March 1 |
| Direct sow outdoors | January 25–February 4 |
| Minimum soil temperature | 40°F |
| Expect first harvest | February 16 – February 24 |
| Fall crop planting | October 18–28 |
| Fall crop harvest | November 9 |
| First fall frost (average) | November 22 |
⚠ Direct sow radishes 4–6 weeks before last frost — one of the fastest crops in the garden. Ready in as little as 22 days. Succession plant every 2 weeks for continuous harvest.
Best Radish Varieties for Simi Valley, CA
Consult a Simi Valley-area nursery or your state extension office for radish varieties proven in Zone 7b.
Growing Radishes in Simi Valley
Simi Valley sits in Zone 7b, with an average last frost of March 1 and first fall frost around November 22 — giving a 266-day frost-free growing season. Cool-season crops like radish benefit from Simi Valley's cooler spring and fall windows, when temperatures stay in the 55–75°F sweet spot that produces the best flavor and least bolting.
Simi Valley's moderate climate supports radish on the standard transplant calendar with minimal special accommodation. Succession planting — sowing fresh seeds or setting new transplants every 2–3 weeks through spring — stretches the harvest window and gives you a backup crop if pests hit the first planting.
Simi Valley's mixed soil conditions vary block by block — get a soil test if you have not in three years. Generally, a base of quality compost (2 to 3 inches annually) and consistent watering at 1 inches per week serves radish well across most soil types found in Simi Valley.
Radish Calendar for Simi Valley
| Month | Task |
|---|---|
| Year | Start seeds indoors under grow lights |
| March | Last frost — soil warming, prepare bed |
| January | Direct sow seeds into warm soil |
| February | Expect first harvest window to open |
| October | Start fall crop — transplants or direct sow |
| November | First fall frost — harvest remaining, end of outdoor season |
Radish Tips for Simi Valley Gardeners
- •Thin to 2-inch spacing when seedlings are an inch tall — crowded radishes produce small woody roots.
- •Succession plant every 10–14 days from early spring through late spring for continuous harvest.
- •Succession plant radish in Simi Valley every 2–3 weeks through spring to extend the harvest window into summer.
Common Radish Pests in Simi Valley
- •Flea Beetle — peaks July in Zone 7b (active May–September); tiny black beetles that riddle leaves with holes; row covers protect seedlings.
- •Cabbage Root Maggot — peaks July in Zone 7b (active May–September); monitor closely during peak season and treat early.
- •Aphid — peaks July in Zone 7b (active May–September); monitor closely during peak season and treat early.
Check plants every 2–3 days during peak season — early intervention prevents most infestations from becoming serious.
What to Plant with Radishes in Simi Valley
In Simi Valley's moderate climate, Lettuce and Carrot are the most beneficial plants to grow alongside radish. Lettuce improves nearby plant health and pest resistance. Keep radish away from Hyssop — it competes for nutrients or shares pest pressure.
Frequently Asked Questions
When should I plant radish in Simi Valley, CA?
In Simi Valley (Zone 7b), direct sow radish around January 25–February 4. Soil must be at 40°F or warmer at 2-inch depth before sowing — cold soil rots the seeds.
What zone is Simi Valley, CA for radish growing?
Simi Valley is USDA Zone 7b. For radish, this means a frost-free growing season of roughly 38 weeks running from March 1 to November 22. Cool-season crops like radish thrive in this zone with both spring and fall planting windows available.
When is radish harvest season in Simi Valley?
Expect the first radish harvest in Simi Valley around February 16, with harvest continuing through February 24. This is based on 22–30 days from transplant or direct sow. A fall crop planted October 18–28 adds a second harvest around November 9.
How long does it take to grow radish in Simi Valley, CA?
From transplant or direct sow to first harvest, radish takes 22–30 days in Simi Valley's climate. Based on a typical planting date of January 25–February 4, expect your first harvest around February 16. Simi Valley's Zone 7b transition-zone climate produces maturity times right in the middle of the stated range.
What soil does radish need in Simi Valley?
Simi Valley's soil conditions vary block by block. Before planting radish, do a soil test (most state extension offices run them for $15–30). The test reveals pH, key nutrient levels, and organic matter content, so you can amend appropriately rather than guessing. Generally, 2–3 inches of compost annually improves most soils for vegetable production.