kale

Best Planting Times for Kale in Idaho

Planting MethodActivityRecommended Dates
Outdoor PlantingIndoor Seed StartingMarch 15 – April 15
Transplant OutdoorsApril 15 – May 15
Fall PlantingDirect Sow OutdoorsAugust 1 – September 1

Planting Conditions

Idaho has a diverse climate ranging from semi-arid in the southern regions to colder, mountainous areas in the north, falling within USDA Hardiness Zones 3b to 7b. The state’s cooler temperatures make it well-suited for growing kale, particularly in the spring and fall.

Plant kale outdoors approximately 4-6 weeks before the last frost in spring, and 6-8 weeks before the first frost in fall.

Average Last Frost Dates for Idaho’s Largest Cities

CityAverage Last Frost Date
BoiseMay 5
MeridianMay 5
NampaMay 10
Idaho FallsMay 20
PocatelloMay 15
CaldwellMay 5
Coeur d’AleneMay 25
Twin FallsMay 15
LewistonApril 30
Post FallsMay 20

Average First Frost Dates for Idaho’s Largest Cities

CityAverage First Frost Date
BoiseOctober 10
MeridianOctober 10
NampaOctober 5
Idaho FallsSeptember 25
PocatelloOctober 1
CaldwellOctober 10
Coeur d’AleneOctober 5
Twin FallsSeptember 30
LewistonOctober 15
Post FallsOctober 5

Please note: These dates are averages and can vary from year to year. It is always a good idea to monitor local weather forecasts and consider your specific location and microclimate when planning your gardening activities.

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Useful Tools for Starting Kale Indoors

Using the right tools can save you time and increase your success rate.

Seeds

Quality seeds lead to better germination and healthier plants. Starting with high-quality seeds gives your kale the best chance to thrive from the very beginning.
Seeds Image
Browse Kale Seeds on Amazon

Planting Trays

Planting trays help you organize your seedlings and ensure they have enough space to grow before you transplant them outdoors. This makes the process more efficient and increases the chances of strong, healthy plants.
Planting Trays Image
Find Planting Trays on Amazon

Grow Lights

Grow lights are essential if you don’t have enough natural sunlight. They provide your seedlings with the light they need to grow strong and healthy, even in less-than-ideal conditions.
Grow Lights Image
Check out Grow Lights on Amazon

Seed Starting Soil

Using light, fine soil specifically designed for seed starting helps young roots establish quickly and promotes healthy growth. It’s an easy way to give your seedlings the best start possible.
Seed Starting Soil Image
Get Seed Starting Soil on Amazon

Garden Tools and Fertilizer

Garden Trowel

A garden trowel is a handy tool that makes transplanting your seedlings easier and more precise, ensuring that each plant is placed at the right depth without damaging the roots.
Garden Trowel Image
Shop Garden Trowels on Amazon

Soil and Fertilizer

Fertilizer is essential for enhancing growth, especially if your soil is nutrient-poor. By enriching the soil, you give your kale plants the nutrients they need to grow robust and produce a bountiful harvest.
Fertilizer Image
Explore Fertilizer on Amazon

Other planting guides for Idaho:

Any questions on growing kale? Visit our forum to discuss: Growing Kale

Starting Kale Indoors

In areas like Boise (Zone 6b), start kale seeds indoors from March 15 to April 15. This timing ensures that seedlings are ready for outdoor transplanting from mid-April to mid-May, after the last frost.

Transplanting Kale Seedlings

Transplant seedlings outdoors from April 15 to May 15, ensuring soil temperatures are consistently above 45°F. Space seedlings 12-18 inches apart in rows at least 18 inches apart to allow for good air circulation and sunlight exposure.

General Care and Maintenance

Watering:

  • Water deeply and consistently to maintain evenly moist soil. Idaho’s semi-arid regions may require more frequent watering, while cooler, mountainous areas may retain moisture longer.
  • Water at the base of the plants to prevent wetting the foliage, which helps reduce the risk of fungal diseases.

Fertilizing:

  • Apply a balanced fertilizer at planting and again when the leaves begin to develop. Adding compost to the soil before planting can improve fertility and soil structure.

Pest and Disease Management:

  • Monitor for common pests like aphids, flea beetles, and cabbage worms. Depending on the region, Idaho’s climate may also encourage fungal diseases, so vigilance is necessary.
  • Use organic or integrated pest management strategies to protect your plants from pests and diseases.

Harvesting Kale:

  • Harvest kale leaves when they are large enough to eat but still tender. Regular harvesting encourages new growth and extends the harvesting season, especially in Idaho’s cooler climates.
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