How to Grow Bulbs in Tucson. A Seasonal Guide with a Focus on Fall Planting

Growing bulbs in Tucson, AZ, may seem challenging due to the region’s hot, arid climate, but with the right approach, bulbs can thrive in this unique desert environment. By choosing the right varieties, timing your planting properly, and providing appropriate care, you can enjoy beautiful blooms throughout the year.

This article will guide you through the best practices for growing bulbs in Tucson, with a special focus on fall planting, which is key to achieving beautiful spring blooms.

Understanding Tucson's Climate for Bulbs

Tucson’s desert climate presents a few distinct challenges for growing bulbs:

• High Summer Temperatures: The extreme heat can be difficult for certain types of bulbs, especially those that require a cold dormancy period.
• Mild Winters with Occasional Frost: While winters are mild compared to colder regions, there can be frosty nights that may affect tender bulbs.
• Low Humidity and Intense Sun: The dry conditions and intense sunlight can stress bulbs if they are not properly mulched or shaded.

Despite these challenges, many bulbs will grow well in Tucson if planted and cared for correctly, especially with attention to seasonal needs.

Best Bulbs for Tucson Gardens

While some bulbs that require extended cold periods may struggle in Tucson, many varieties are well-suited to the climate. The following bulbs are recommended for Tucson gardens:

• Daffodils (Narcissus): Particularly hardy in warm climates.
• Tulips (Tulipa): Select low-chill varieties or treat as annuals by planting fresh bulbs each year.
• Iris (Iris germanica): Bearded irises are particularly drought-tolerant once established.
• Amaryllis (Hippeastrum): These striking flowers do quite well in desert climates.
• Freesia (Freesia spp.): These bulbs perform well in mild winters and provide beautiful, fragrant blooms.
• Anemone (Anemone coronaria): This hardy bulb does well in Tucson and blooms reliably in the spring.
• Allium (Allium spp.): These bulbs are heat-tolerant and can thrive in Tucson’s climate.
• Ranunculus (Ranunculus asiaticus): These bulbs will produce vibrant blooms and are fairly heat-tolerant.

Seasonal Guide for Growing Bulbs in Tucson

Fall: The Ideal Time for Planting Bulbs

Fall is the most important season for planting bulbs in Tucson if you want vibrant blooms in the spring. The key to success is planting when the weather begins to cool down but before the first frost arrives.

Timing Your Planting

• In Tucson, the best time to plant bulbs is mid-October to mid-December. This allows the bulbs to establish their roots during the cooler months and develop properly for a spring bloom.
• Bulbs that require chilling (like tulips) should be refrigerated for 4 to 6 weeks before planting if they haven’t been pre-chilled.

Preparing the Soil

• Soil Preparation: Bulbs require well-draining soil, which can be a challenge in some Tucson areas where the soil tends to be clay-heavy. Amend the soil with organic material like compost or well-rotted manure to improve drainage and enrich the soil.
• Digging Depth: A general rule of thumb for planting bulbs is to dig a hole two to three times the height of the bulb. For most bulbs in Tucson, this means planting them 3-6 inches deep. Tulips and daffodils should be planted deeper (6-8 inches) to protect them from temperature fluctuations.
• Watering After Planting: Water the bulbs deeply after planting to encourage root development. Keep the soil moist (but not soggy) throughout the winter as the bulbs establish.

Mulching

• Apply a 2-3 inch layer of mulch over the bulb bed to insulate the soil and maintain moisture levels. Mulch will also help protect the bulbs from sudden temperature drastic temperature fluctuations, which can happen in Tucson’s winter months.

Chill Requirements

• Some bulbs, like tulips and hyacinths, require a cold period to bloom properly. Tucson’s winters may not always provide enough chilling hours naturally. For these types of bulbs, refrigerating them for 4-6 weeks before planting will simulate their required dormancy period. Be sure to keep the bulbs in a paper bag in the refrigerator and away from fruits like apples, which release ethylene gas and can prevent the bulbs from blooming.

Winter: Caring for Bulbs as They Develop

In Tucson, winter temperatures are generally mild, but it’s still essential to care for your bulbs as they begin to develop underground.

Monitoring Frost

• While Tucson’s winters are typically mild, there can be frost during December and January. Monitor weather reports and cover your bulb beds with frost cloth on cold nights to protect the young shoots from damage.

Watering in Winter

• Continue to water your bulbs throughout the winter. Tucson’s dry climate means bulbs may need supplemental water, even during the cooler months. However, be mindful not to overwater, as waterlogged soil can lead to bulb rot. Aim for moist, not soggy, soil.

Fertilizing

• Once the shoots start to emerge in late winter (January or February), feed your bulbs with a balanced, slow-release fertilizer to give them the nutrients they need for optimal bloom production.

Spring: Enjoying the Bloom and Post-Bloom Care

Spring is the reward for your fall planting efforts. Depending on the bulb type, you’ll start to see blooms in February through April.

Caring for Blooming Bulbs

• Continue to water your bulbs regularly during their bloom period. Tucson’s spring can be dry and warm, so make sure they receive consistent moisture.
• Deadhead spent flowers to encourage the plant to put energy into building up the bulb for next year’s bloom cycle, rather than producing seeds.

Post-Bloom Care

• Once the flowers have faded, allow the foliage to die back naturally. This process is essential as the leaves help photosynthesize and store energy in the bulb for next season.
• Avoid cutting back the foliage until it has completely yellowed and withered, which usually occurs by late spring or early summer.

Summer: Resting and Storing Bulbs

Tucson’s intense summer heat presents a challenge for bulbs, many of which require a period of dormancy to survive the extreme temperatures.

Watering Dormant Bulbs

• After the foliage has died back, reduce watering to almost nothing. Most bulbs, especially those adapted to desert climates, prefer dry conditions during dormancy. Overwatering during this period can lead to rot.

Mulch and Shade

• To protect dormant bulbs from the summer heat, leave a layer of mulch over the bed to insulate the soil. If possible, plant bulbs in areas that receive afternoon shade to help keep the soil cooler.

Storing Tender Bulbs

• Some tender bulbs, such as certain species of dahlias, calla lilies, and gladiolus, may not tolerate Tucson’s summer heat well. In these cases, you can dig up the bulbs after the foliage has died back and store them in a cool, dry place (like an air-conditioned garage or closet) until it’s time to replant in the fall.

Additional Tips for Growing Bulbs in Tucson

1. Choose Heat-Tolerant Bulbs
   • While Tucson’s desert climate can be challenging, selecting bulbs that are adapted to or tolerant of hot climates will increase your chances of success. Many Mediterranean-origin bulbs, such as narcissus, alliums, and irises, are well-suited to Tucson’s climate.

2. Containers for Bulbs
   • If you have trouble with soil drainage or want more control over the growing environment, consider planting bulbs in containers. Make sure the pots have good drainage and water the bulbs regularly. In summer, move the pots to a shaded area to protect them from the worst of the heat.

3. Companion Planting
   • Consider planting your bulbs with perennials or shrubs that can help provide shade during the summer months. This will keep the soil cooler and help prevent stress on the dormant bulbs.

Growing bulbs in Tucson, Arizona, requires some special considerations, particularly with the timing of fall planting and managing the dry, hot conditions during dormancy. However, with the right selection of bulbs, proper soil preparation, and attention to seasonal needs, you can enjoy a spectacular display of flowers in your desert garden year after year. By planting in the fall, providing adequate watering, protecting from frost, and allowing bulbs to go dormant in the summer, your Tucson garden can become a vibrant showcase of bulb blooms despite the challenging climate.