When to Plant Cosmos in Haiku, Hawaii (96708)

Location

Haiku, Hawaii

ZIP Code

96708

USDA Zone

12a

Last Frost

Thursday, January 1, 2026

📅 Your 2026 Planting Dates

Direct Sow Outdoors

Thursday, January 1, 2026

Based on last frost Thursday, January 1, 2026 · Zone 12a

Pro tip: Sow Cosmos directly outdoors around your last frost date when soil starts to warm.

Add to Calendar (.ics)

🌿 Plant Details

Scientific Name Cosmos bipinnatus

Days to Maturity 60 days

Mature Height 24-60"

Spread 18"

Type Annual

☀️ Growing Requirements

☀️

Sun

Full Sun (6-8 hours)

💧

Water

Low-Moderate

↔️

Spacing

18" apart

🌱

Planting Depth

0.25" deep

Seeds typically germinate in 7-14 days

Ready to Plant Cosmos in Haiku?

Get your seeds now so they're ready by Thursday, January 1, 2026.

🛒 Buy on Amazon 🌿 True Leaf Market

* Affiliate links — we may earn a small commission at no extra cost to you.

🤝 Good Companions

CornSquashTomato

🤝

Full Companion Planting Guide for Cosmos

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

🛠️ Supplies You'll Need

🌍 Flower Garden Soil ✂️ Pruning Shears 🚿 Watering Can

* Affiliate links — we may earn a small commission at no extra cost to you.

🌾 Seed Saving Guide

🟢 Easy

✅ Open-pollinated — seeds grow true to parent

When to Harvest Seed

Harvest narrow seed heads when flower petals drop and the base turns brown and dry.

Processing

Pull seeds directly from dried flower heads, dry 1 week in an open envelope.

Seed Viability

Up to 3 years when stored cool, dark, and dry.

Pro Tip

Cosmos cross freely within the species — isolate by 150 feet from other cosmos for pure color.

🪴

Raised Bed Planting Guides

A 4×8 bed fits 14 plants of Cosmos. See plant counts, spacing grids, and companion pairings for every bed size →

Frequently Asked Questions

When should I plant Cosmos in Haiku, Hawaii? +

In Haiku (Zone 12a), direct sow Cosmos outdoors around Thursday, January 1, 2026.

What is the last frost date for Haiku, Hawaii? +

The average last spring frost date for Haiku, Hawaii (ZIP 96708) is around Thursday, January 1, 2026. This is based on NOAA climate normals for USDA Zone 12a.

How long does Cosmos take to grow? +

Cosmos typically matures in about 60 days from direct sowing. In Haiku, that means you can expect harvest around Thursday, January 1, 2026 plus 60 days.

Should I start Cosmos indoors or direct sow in Hawaii? +

Cosmos does best when direct sown outdoors. In Haiku, sow directly around Thursday, January 1, 2026.

📚 More Cosmos Planting Guides

🗺️

Cosmos in Hawaii

Zone-by-zone breakdown · Full state guide

→ 🌡️

Zone 12a Cosmos Guide

All cities in your zone · Avg dates

→

Other Plants for Haiku

Blackberry Blueberry Raspberry Strawberry Basil Chamomile Chives Cilantro Dill Lavender Lemon Balm Marjoram Mint Oregano Parsley Rosemary Sage Tarragon Thyme Acorn Squash Artichoke Arugula Asparagus Beefsteak Tomato Beet Bell Pepper Bok Choy Broccoli Brussels Sprout Butternut Squash Cabbage Cantaloupe Carrot Cauliflower Cayenne Pepper Celery Cherry Tomato Chili Pepper Collard Green Common Bean Cucumber Eggplant Endive Fennel Garlic Grape Tomato Green Bean Habanero Pepper Head Lettuce Heirloom Tomato Honeydew Melon Jalapeño Pepper Kale Kohlrabi Leaf Lettuce Leek Lima Bean Mustard Okra Onion Parsnip Pea Poblano Pepper Pole Pea Potato Pumpkin Radicchio Radish Rhubarb Roma Tomato Rutabaga Serrano Pepper Shallot Snap Pea Snow Pea Spaghetti Squash Spinach Squash Sweet Corn Sweet Potato Swiss Chard Tomato Turnip Watermelon Zucchini Sunflower Marigold Zinnia Nasturtium Echinacea (Coneflower) Petunia Black-eyed Susan Apple Tree Pear Tree Peach Tree Plum Tree Sweet Cherry Tree Lemon Tree Borage Lemongrass Ginger Stevia Tomatillo Edamame Fava Bean Mâche Mizuna Sorrel Shishito Pepper Banana Pepper Watermelon Radish Napa Cabbage Popcorn Broccoli Raab Catnip Valerian Lemon Verbena Bee Balm Anise Lovage Chervil Summer Savory Dahlia Snapdragon Pansy Sweet Pea Morning Glory Hollyhock Larkspur Bachelor Button Columbine Impatiens Salvia (Annual) Sweet Alyssum Celosia Lupine Verbena Elderberry Grape Vine Red Currant Gooseberry Serviceberry Fig Tree Avocado Tree Persimmon Tree Olive Tree

Growing Cosmos in Zone 12a

Cosmos (Cosmos bipinnatus) is a popular garden vegetable. In Haiku, Hawaii, which is in USDA Hardiness Zone 12a, you should direct sow seeds around Thursday, January 1, 2026.

Your average last frost date is Thursday, January 1, 2026. Cosmos grows well when direct sown, as it doesn't transplant well or germinates quickly outdoors.