When to Plant Watermelon in Hilo, Hawaii (96721)

Location

Hilo, Hawaii

ZIP Code

96721

USDA Zone

12b

Last Frost

Thursday, January 1, 2026

📅 Planting Calendar

Start Seeds Indoors Thursday, December 4, 2025

Transplant Outdoors Thursday, January 15, 2026

Pro Tip: Start Watermelon seeds indoors 4 weeks before your last frost date, then transplant outdoors around Thursday, January 15, 2026.

🌿 Plant Details

Scientific Name Citrullus lanatus

Days to Maturity 80 days

Mature Height 12-24"

Spread 72"

Type Vine

Fruit Size Large (10-30 lbs)

☀️ Growing Requirements

☀️

Sun

Full Sun (8+ hours)

💧

Water

Regular (1-2 inches/week)

↔️

Spacing

72" apart

🌱

Planting Depth

1" deep

Seeds typically germinate in 4-12 days

Ready to Plant Watermelon in Hilo?

Get your seeds now so they're ready by Thursday, December 4, 2025.

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🤝 Good Companions

CornSunflowerMarigold

⚠️ Avoid Planting Near

Potato

Other Plants for Hilo

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 Zucchini Sunflower Marigold Zinnia Nasturtium Cosmos 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 Watermelon in Zone 12b

Watermelon (Citrullus lanatus) is a popular garden vegetable. In Hilo, Hawaii, which is in USDA Hardiness Zone 12b, you should start seeds indoors around Thursday, December 4, 2025.

Your average last frost date is Thursday, January 1, 2026. Plan to transplant your Watermelon seedlings outdoors around Thursday, January 15, 2026, about 2 weeks after your last frost date.