January is a pivotal month for gardeners in Tucson, offering the perfect mix of cool weather and dormant plant cycles. While the desert landscape might seem quiet, this is an ideal and essential time to prune, plant, and prepare your garden for the coming spring. With careful attention to tasks like pruning roses, amending soil, planting trees, and protecting frost-sensitive plants, your garden can thrive year-round.
Pruning Roses
January is the prime time to prune roses in Tucson. This ensures robust blooms in spring and a healthier, more vigorous plant overall. Follow these steps for optimal results:
- Timing: Prune mid-to-late January, before buds begin to swell.
- Technique: Remove 1/2 to 2/3 of the bush’s height, cutting back mature bushes to about 2-4 feet. Focus on removing dead canes, twiggy growth, and any canes crossing or rubbing against others.
- Cut Placement: Make cuts 1/4 inch above an outward-facing bud eye at a 45-degree angle. This encourages outward growth and improves air circulation.
- Defoliation: Strip all remaining leaves to remove potential sources of fungal spores or pests. Make sure to dispose of these as quickly as possible, keeping them off the ground to prevent fungal spores and pest from spreading.
- Clean-Up: Dispose of all debris in the trash, not the compost, to avoid spreading diseases or overwintering pests.
- Aftercare: Apply a dormant spray, such as a combination of horticultural oil and fungicide, to protect against pests and diseases. Ensure thorough coverage of the canes and surrounding soil.
Planting Dormant and Evergreen Trees
January’s cooler temperatures and lower water needs make it an ideal time to plant trees.
- Dormant Trees:
- Choose dormant varieties of fruit and nut trees like peaches, plums, mulberry, and almonds. These trees establish very quickly when planted during dormancy.
- Dig a wide, shallow hole, ensuring the graft union (where the tree was grafted onto rootstock) sits 1-2 inches above the soil line. Be careful not to plant trees below soil grade. The root flare, where the roots come off the trunk, should be just visible above the soil. This area acts largely as the “lungs” of a tree and need access to oxygen to complete the plant’s biological processes.
- Evergreen Trees:
- Some suitable choices include citrus trees, olives, mastic trees, cypress, and Texas ebony.
- Plant in a location with good drainage, avoiding areas prone to frost pockets.
- Mulch around the base to conserve moisture and regulate soil temperature.
- Make sure the tree is planted slightly above the soil level so that as it settles it will be at grade.
- Watering: After planting, water deeply to settle the soil around the roots. Continue with regular watering but avoid overwatering during cooler months.
Remember slow and deep is the key with watering. Roots cannot grow into dry soil, so deep watering is essential to healthy root establishment.
Amending the Soil
Tucson’s alkaline and often nutrient-poor soils can benefit greatly from amendments:
- Organic Matter: Add well-rotted compost or manure to improve soil structure and nutrient content. Doing this a couple times a year as a 2-4″ topdressing will bring much needed fertility to garden beds.
- Clay Soils: Incorporate gypsum to break up heavy clay and improve drainage.
- Alkaline Soils: Use soil sulfur or organic soil acidifiers to lower pH and enhance nutrient availability. This will benefit almost all non-native plants.
- Application: Work amendments into the top 6-8 inches of soil during initial garden bed installation. Top dressing or side dressing in subsequent years will continuously improve soil structure and fertility.
Transplanting Advice
Cool, mild mornings in January provide ideal conditions for transplanting shrubs, trees, and perennials to a new location in the garden.
- Preparation: Water plants thoroughly before moving them to reduce stress on the roots. Doing this the day before works best.
- Digging: Carefully dig around the root ball to minimize root damage.
- Replanting: Position the plant at the same depth it was growing previously. Backfill with amended native soil and water thoroughly.
- Aftercare: Use a root stimulator to promote root growth, and apply mulch to retain moisture. Protect transplants with frost cloth if freezing temperatures are forecasted.
Harvesting Citrus
January is peak citrus season in Tucson, with oranges, lemons, grapefruits, and kumquats ready for harvest.
- Ripeness Check: Taste-test fruit for sweetness. Mature fruit may remain on the tree for weeks without spoiling.
- Harvesting Tools: Use hand clippers or a sharp knife to avoid tearing the skin or damaging the tree.
- Storage: Store citrus in a cool, dry place to extend freshness. Avoid prolonged exposure to direct sunlight post-harvest.
Pruning Grapevines
Pruning grapevines in January sets the stage for a productive growing season. Grapes must be pruned hard to set fruit.
- Timing: Complete pruning before bud break. Once winter rains and temperatures rise the buds will begin to swell and make pruning more difficult. Grapes can produce a lot of sap, so pruning while temperatures are lower during dormancy will help mitigate bleeding.
- Techniques: Remove up to 80% of last year’s growth. Leave 2-3 buds per spur on each cane to direct energy toward fruit production.
- Clean-Up: Dispose of pruned material and fallen leaves to reduce the risk of pest and disease carryover. Powdery mildew can easily overwinter on old tissue and reinfect the plant come spring.
Pest Management: Gray Aphids
Gray aphids can be a common pest in Tucson gardens during winter months:
- Identification: Look for curling leaves, sticky honeydew, or sooty mold.
- Control: Spray affected plants with insecticidal soap or neem oil. Repeat treatments every 7-10 days if needed. A strong jet of water will also knock them off foliage.
- Prevention: Encourage beneficial insects like ladybugs and lacewings to help control aphid populations naturally.
Winter Weeding
Cool-season weeds like Russian thistle (tumbleweed), goat’s head, purslane, and London rocket thrive in January’s mild weather:
- Hand Pulling: Remove weeds while they’re small to prevent seeding. This is especially effective after a winter rain. One flower will produce enough seeds for seven years of weeds, so pull or remove them before they set seed.
- Mulching: Apply a 2-3 inch layer of mulch around plants to suppress weed growth.
- Pre-Emergent Herbicides: Apply in garden beds to prevent weed seeds from germinating.
Cold Protection for Frost-Sensitive Plants
Frost-sensitive plants like bougainvillea, citrus, and succulents need special care during Tucson’s chilly nights. Protecting frost sensitive plants a few nights a year can save years of growth from being damaged.
- Covering: Use frost cloth or old sheets to cover plants when temperatures drop below 32°F. Ensure the cover reaches the ground to trap warmth and ideally have it lifted several inches off the foliage.
- Watering: Water plants thoroughly before a freeze; moist soil retains heat better than dry soil. Do this early in the day to capture as much heat as possible.
- Potted Plants: Move containers to sheltered locations or indoors if possible.
- If plants are damaged from cold, do not rush to prune them. Once the weather warms up new buds will sprout, and you can then remove the dead wood and foliage.
January is a month of preparation and renewal for Tucson gardens. By tackling pruning, planting, amending, and pest management tasks now, you set the stage for a vibrant and productive growing season. With thoughtful care and attention, your garden will not only survive the challenges of winter but thrive in the months ahead. Take advantage of Tucson’s mild climate and enjoy the rewards of a well-tended garden year-round.