Gardening in Tucson during December is an enjoyable and rewarding experience, thanks to the region’s mild winters and ample sunshine. While the cooler temperatures bring some challenges, such as frost risks, they also present an opportunity to prepare for the upcoming spring growing season. In this article, we’ll cover important tips for seed starting, ideal annual flowers to plant in December, and watering strategies when temperatures drop.
1. Seed Starting for Early Spring Planting
Although December is one of the colder months in Tucson, it’s an excellent time to begin preparing for the spring gardening season, especially for crops like tomatoes and greens. Starting seeds indoors allows you to give plants a head start and ensure they are strong and healthy by the time the weather warms up.
Tomatoes
Tomatoes are a popular crop in Tucson’s spring and summer gardens, and December is the perfect month to start tomato seeds indoors. Starting seeds now allows the plants to grow strong and be ready for transplanting in late February or early March, once the danger of frost has passed.
- Selecting Tomato Varieties: Choose tomato varieties that are well-suited to Tucson’s hot, dry climate. Look for heat-tolerant varieties like ‘Sun Gold,’ ‘Roma,’ and ‘Celebrity,’ which perform well in the desert environment. You can also opt for smaller, quicker-maturing varieties, such as cherry or determinate tomatoes, that reach harvest more rapidly.
- Starting Seeds Indoors: Use seed trays or small pots filled with seed-starting mix. Place the trays in a warm, sunny spot or under grow lights to ensure proper germination. Tomatoes require soil temperatures between 70°F and 80°F for the best germination rates. Keep the soil moist but not soggy, and once the seedlings emerge, thin them out to ensure healthy growth.
- Transplanting Outdoors: Tomato seedlings can be transplanted into the garden once the outdoor temperatures consistently stay above 50°F (10°C). Be sure to harden off the plants by gradually exposing them to outdoor conditions for a week before planting them in the ground.
Greens (Lettuce, Spinach, Kale, Arugula)
Cold-hardy greens thrive in Tucson’s mild winter climate and can be directly sowed in the ground or started indoors in December.
- Direct Seeding vs. Indoor Starting: You can start greens directly in your garden, but starting them indoors allows for an earlier harvest. To start greens indoors, use shallow containers with a well-draining mix. Once they have developed two sets of true leaves, they can be transplanted into your garden or raised beds.
- Varieties to Grow: Ideal winter greens for Tucson include:
- Lettuce: Varieties like ‘Butterhead,’ ‘Romaine,’ and ‘Mesclun’ are great choices.
- Spinach: Opt for varieties like ‘Bloomsdale’ or ‘Tyee,’ which are cold-tolerant.
- Kale: Varieties like ‘Winterbor’ and ‘Dwarf Blue Curled’ grow well in winter.
- Arugula: This peppery green thrives in the cool Tucson winters.
- Sowing Outdoors: For greens grown directly in the garden, sow seeds ¼ to ½ inch deep in rows or containers. Water the seeds well after planting, but avoid overwatering. These plants will sprout quickly in the cooler December temperatures, especially when protected by row covers or cloches if frost is expected.
2. Ideal Annual Flowers for December Planting
While many plants in Tucson may be dormant during December, there are several annual flowers that thrive in the cooler temperatures. Planting these flowers now ensures that your garden bursts into color come spring, while also providing beauty during the winter months.
Cool-Season Annuals
These flowers love the cooler temperatures of Tucson’s winter months, and many will bloom well into spring, giving your garden a long-lasting display of color.
- Pansies: Known for their vibrant colors and ability to handle cool temperatures, pansies are an ideal choice for December planting in Tucson. They come in a variety of colors and patterns, adding a cheerful touch to garden beds, containers, or hanging baskets. Pansies will bloom through the winter and early spring, providing a consistent splash of color.
- Violas: Similar to pansies, violas are another hardy annual flower that thrives in the cooler months. Violas are smaller than pansies but have a similarly wide range of colors. Plant them in well-drained soil with plenty of sunlight to ensure vibrant blooms throughout the winter and into the spring.
- Snapdragons: These flowers are perfect for Tucson’s mild winter, as they can tolerate the cooler temperatures without issue. They will bloom from December through spring, providing vertical interest and bright colors in your garden. Snapdragons prefer full sun but can tolerate some afternoon shade in the desert heat.
- Calendula: Known for its bright, cheerful blooms, calendula is a great flower to plant in December. This flower thrives in cooler weather and will continue blooming through winter and early spring. Calendula is perfect for beds or containers, and its flowers attract beneficial pollinators to your garden.
- Stock: Stock is another excellent choice for winter gardens. It is known for its fragrance and colorful spikes of blooms in shades of pink, white, purple, and red. Stock will thrive in Tucson’s winter temperatures and provides great cut flowers for arrangements.
- Sweet Peas: If you want a fragrant addition to your garden, consider planting sweet peas. These climbing plants will begin to show their delicate, colorful flowers in early spring and continue blooming throughout the season. Plant them in December for an early start.
Planting Tips for Annuals in December
- Plant flowers in well-drained soil and ensure they are spaced properly for good air circulation.
- Mulch around newly planted flowers to help retain moisture and maintain a stable soil temperature.
- Be mindful of frost: If an unexpected frost is forecast, cover the flowers with frost cloth or blankets to protect them.
3. Watering Strategies During Cooler Months
Watering in Tucson’s winter months can be tricky due to the lower temperatures and drier air. Proper watering techniques are essential to prevent overwatering, which can lead to root rot, and underwatering, which can stress plants during the colder weather.
How to Water in December
- Morning Watering: During December, water your garden early in the morning, especially before temperatures dip in the evening. Watering in the morning ensures that moisture is absorbed by plant roots before nighttime cold causes it to freeze or evaporate too quickly.
- Watering Frequency: While it’s tempting to water less often in winter, your plants still need hydration, especially in Tucson’s dry desert environment. The key is to adjust your watering schedule based on the weather:
- For cool-season plants like greens and flowers, water deeply once every 5–7 days.
- For desert-adapted plants, such as succulents and cacti, reduce watering to every 2–3 weeks, depending on rainfall and temperature.
- Watering When It’s Cold: When temperatures drop near freezing, it’s crucial not to water late in the day. Wet soil at night can freeze, potentially damaging plant roots. If you’re concerned about frost, water in the morning so that soil moisture can help buffer temperature extremes.
- Drip Irrigation: Drip irrigation is ideal for conserving water while providing steady moisture to plants. In winter, adjust your drip system to run for shorter intervals but at slightly longer durations to ensure deep watering without waterlogging the soil. Avoid sprinklers during the winter months, as they can create pools of water that may freeze.
- Soil Moisture: Check the soil moisture regularly, especially in areas with poor drainage. Use a moisture meter or simply check the soil with your finger; if it’s dry a few inches down, it’s time to water. Avoid allowing the soil to remain too wet, as this can cause root rot, particularly for winter vegetables and annual flowers.
Conclusion
December in Tucson is an important month for planning, planting, and preparing for the upcoming spring garden. By starting seeds indoors for early spring crops like tomatoes and greens, planting cool-season annual flowers, and adjusting your watering practices to suit the cooler temperatures, you’ll set the foundation for a successful garden in the warmer months. Whether you’re growing vegetables, flowers, or both, December offers opportunities to nurture your garden and look forward to vibrant blooms and bountiful harvests.