When to Plant Mustard in Mount Wilson, California (91023)

Location

Mount Wilson, California

ZIP Code

91023

USDA Zone

Last Frost

Friday, February 20, 2026

📅 Your 2026 Planting Dates

Direct Sow Outdoors

Friday, January 9, 2026

Based on last frost Friday, February 20, 2026 · Zone 9a

Pro tip: Sow Mustard directly outdoors 6 weeks before your last frost date.

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🌿 Plant Details

Scientific Name Brassica juncea

Days to Maturity 56 days

☀️ Growing Requirements

☀️

Sun

Full Sun

💧

Water

Regular

Seeds typically germinate in 1-7 days

Ready to Plant Mustard in Mount Wilson?

Get your seeds now so they're ready by Friday, January 9, 2026.

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🤝 Good Companions

CabbageCauliflowerRadishBrussel SproutTurnip

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Full Companion Planting Guide for Mustard

See which plants help Mustard thrive, which to keep away, and raised bed layout tips →

🛠️ Supplies You'll Need

🪵 Raised Garden Bed 🌍 Vegetable Garden Soil 🛠️ Hand Trowel Set 🚿 Watering Can

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🌾 Seed Saving Guide

🟢 Easy

✅ Open-pollinated — seeds grow true to parent

When to Harvest Seed

Harvest seed pods just as they turn tan — before they shatter and seeds drop.

Processing

Cut stalks into a bag, thresh to release seeds from pods, winnow lightly.

Seed Viability

Up to 4 years when stored cool, dark, and dry.

Pro Tip

Mustard crosses freely within the Brassica family — isolate by 300 feet from other mustard varieties.

Frequently Asked Questions

When should I plant Mustard in Mount Wilson, California? +

In Mount Wilson (Zone 9a), direct sow Mustard outdoors around Friday, January 9, 2026.

What is the last frost date for Mount Wilson, California? +

The average last spring frost date for Mount Wilson, California (ZIP 91023) is around Friday, February 20, 2026. This is based on NOAA climate normals for USDA Zone 9a.

How long does Mustard take to grow? +

Mustard typically matures in about 56 days from direct sowing. In Mount Wilson, that means you can expect harvest around Friday, January 9, 2026 plus 56 days.

Should I start Mustard indoors or direct sow in California? +

Mustard does best when direct sown outdoors. In Mount Wilson, sow directly around Friday, January 9, 2026.

📚 More Mustard Planting Guides

🗺️

Mustard in California

Zone-by-zone breakdown · Full state guide

→ 🌡️

Zone 9a Mustard Guide

All cities in your zone · Avg dates

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Growing Mustard in Zone 9a

Mustard (Brassica juncea) is a popular garden vegetable. In Mount Wilson, California, which is in USDA Hardiness Zone 9a, you should direct sow seeds around Friday, January 9, 2026.

Your average last frost date is Friday, February 20, 2026. Mustard grows well when direct sown, as it doesn't transplant well or germinates quickly outdoors.