Geranium in Zone 10B — Desert Southwest

Geraniums bring a vibrant splash of color to our Desert Southwest gardens, adding beauty to beds and containers. Their ability to thrive in our sunny climate, with proper care, makes them a rewarding choice for any gardener looking for long-lasting blooms.

Sure, our extreme heat and alkaline soil present challenges, but with our long growing season and strategic timing, growing geraniums is definitely achievable. You have two distinct growing seasons to work with, giving you a wide window of opportunity to enjoy these lovely flowers.

Starting geraniums from seed indoors can be a good option, especially if you want a specific variety. Start your seeds indoors from late October through mid November, about 12 weeks before you plan to transplant them outside.

Use seed trays with a good seed-starting mix. Keep the soil consistently moist, and provide warmth and plenty of light – a grow light works wonders. Bottom watering can help prevent damping-off disease. Given our very-early spring character, getting a head start indoors gives you an edge.

Transplanting geraniums outdoors should happen from late January through late February. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense Desert Southwest sun and wind.

Plant them 10-12 inches apart in well-draining soil. Geraniums are notoriously slow from seed, so buying established starts from a local nursery might be an easier and faster way to enjoy their blooms.

Watering is key to geranium success in our arid climate. While geraniums need moderate watering, avoid letting them sit in soggy soil, which can lead to stem rot. Let the top inch or two of soil dry out between waterings.

During the cooler months, you might only need to water once a week, but during our extreme summer heat, increase watering to 2-3 times a week. Use the finger test: stick your finger about two inches into the soil. If it feels dry, it's time to water. Aim for about an inch of water per week, adjusting for rainfall. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal issues in our desert environment.

Signs of underwatering include wilting leaves and dry, crispy edges. Overwatering, on the other hand, can cause yellowing leaves and stem rot. A layer of organic mulch around the base of the plant helps retain moisture and regulate soil temperature, which is crucial in our extreme heat.

Regular pruning keeps your geraniums looking their best and encourages more blooms. Deadhead spent flower clusters by snipping them off at the base of the stem. This directs the plant's energy into producing new flowers instead of seeds.

Throughout the growing season, pinch back any leggy stems to promote bushier growth. As our first frost approaches around late December, you can give your geraniums a final trim to tidy them up before winter.

With proper care, you can expect your first geranium blooms from early April through late May. Geraniums are primarily grown for their beautiful flowers, so "harvesting" in this case means enjoying their beauty in your garden. Regularly remove faded blooms to maintain a neat appearance and encourage continuous flowering throughout the season.

Harvest the flowers by snipping the stem just above a leaf node. There is no need to ripen the flowers off the vine. As the season winds down and our first frost approaches in late December, consider taking cuttings to propagate new plants indoors for next year.

Here are some common problems you might encounter growing geraniums in the Desert Southwest:

Botrytis Blight *What it looks like:* Grayish-brown mold on leaves, stems, and flowers, often starting with water-soaked spots. *What causes it:* High humidity and poor air circulation, which can occur during our monsoon season. *How to fix/prevent it:* Improve air circulation by spacing plants adequately. Remove and destroy affected plant parts. Avoid overhead watering, especially in humid weather.

Geranium Budworm *What it looks like:* Holes in buds and flowers, chewed leaves, and small green caterpillars present on the plant. *What causes it:* These caterpillars are the larvae of moths that lay their eggs on geraniums. *How to fix/prevent it:* Handpick caterpillars when you see them. Use insecticidal soap or Bacillus thuringiensis (Bt) to control infestations.

Edema *What it looks like:* Small, blister-like bumps on the undersides of leaves, which can turn brown and corky. *What causes it:* Inconsistent watering and cool, humid conditions, leading to the plant taking up more water than it can transpire. *How to fix/prevent it:* Ensure consistent watering, avoiding extremes of wet and dry. Improve air circulation around plants.

Desert Southwest Specific Challenges: The extreme heat and intense sun can stress geraniums, making them more susceptible to pests and diseases. Our arid climate can also lead to edema if watering isn't consistent. During the monsoon season, be extra vigilant about botrytis blight.

Geraniums make great companions for several plants in the Desert Southwest garden. Plant them near tomatoes and peppers to help deter certain pests. The strong scent of geraniums can also help repel insects from corn. Roses also benefit from geraniums as companions, as they can deter Japanese beetles. Avoid planting geraniums near fennel, as it can inhibit their growth.