Geranium in Zone 8B — Northern California

Growing geraniums in Northern California is rewarding. Their vibrant colors brighten our gardens and containers, plus they're relatively low-maintenance. With our long growing season and mild winters, you can enjoy their blooms for a good portion of the year.

While we face challenges like drought and occasional heat waves, geraniums are surprisingly resilient if you manage their water well. Our 269-day growing season gives you ample time to get them established and thriving.

Starting geraniums from seed indoors is possible, but be warned: they are notoriously slow growers. If you're patient and enjoy the process, starting seeds indoors from mid December through early January (about 12 weeks before transplanting) is a good option.

Use seed trays with a good seed-starting mix, and keep them consistently warm (around 70-75°F) and well-lit. Consider using a heat mat and grow lights to help them along. Bottom watering is great for seedlings to prevent damping off.

Given our early springs here in NorCal, getting a head start indoors can give you larger, more established plants to set out when the weather warms up. But honestly, for most of us, buying starts from a local nursery is the easier route.

Transplant your geraniums outdoors from mid March through mid April, once the danger of frost has passed. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week.

Space them 10-12 inches apart in a sunny spot with well-drained soil. Even in mid-March, we can still get unexpected cool snaps, so keep an eye on the forecast and be ready to cover them if needed. For the easiest results, just buy starts.

Geraniums need moderate watering, especially during our dry summers here in Northern California. Let the soil dry out slightly between waterings; they definitely don't like soggy feet. Overwatering is a quick path to stem rot.

During the cooler spring months, you might only need to water once a week, or even less if we're getting rain. But come summer, with our moderate-to-hot heat and low humidity, you'll likely need to water every 2-3 days. Stick your finger about 2 inches deep into the soil – if it feels dry, it's time to water. Aim for about an inch of water per week, delivered at the base of the plant to avoid wetting the foliage.

Signs of underwatering include wilting leaves and dry, crumbly soil. Overwatering, on the other hand, can lead to yellowing leaves and mushy stems. A layer of mulch around the base of the plants can help retain moisture and keep the soil cool during the hotter months.

Deadheading is key to keeping your geraniums blooming throughout the season. Simply pinch off the spent flower clusters as soon as they start to fade. This encourages the plant to put its energy into producing new blooms instead of seeds.

If you notice any leggy stems, pinch them back to encourage bushier growth. As we approach late November and the first frost, you can cut back the plants to tidy them up. In our mild NorCal winters, they might even keep some foliage.

Geraniums aren't exactly a "harvest" crop in the traditional sense, but you'll start to see blooms from late May through mid July, about 70 days from transplant. Instead of harvesting, you're really maintaining the plant for continuous flowering.

The "harvest" is the enjoyment of the flowers themselves. Regularly remove any faded or dead blooms to keep the plants looking tidy and encourage more flowers. This is especially important during our long growing season here in NorCal.

As late November approaches and the first frost threatens, you can bring potted geraniums indoors to overwinter, or take cuttings to propagate new plants. Otherwise, just enjoy the last of the blooms before the cold weather sets in.

Here are three common problems you might encounter with geraniums in Northern California:

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. While NorCal is generally dry, morning fog in coastal areas or overly dense plantings can create favorable conditions.
• How to fix/prevent it: Improve air circulation by spacing plants properly. Remove infected leaves and flowers promptly. Avoid overhead watering, especially in the evening.

Geranium Budworm

• What it looks like: Small holes in buds and flowers, often with dark droppings nearby. The budworms themselves are small, green caterpillars.
• What causes it: Moths lay eggs on the plants, and the larvae (budworms) feed on the buds and flowers.
• How to fix/prevent it: Inspect plants regularly for budworms. Handpick them off or use Bacillus thuringiensis (Bt), a biological insecticide.

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. Edema is caused by the plant taking up more water than it can transpire, often during cool, cloudy weather after a period of drought.
• How to fix/prevent it: Ensure consistent watering and good drainage. Avoid letting the soil dry out completely between waterings, especially during temperature swings.

Northern California Specific Challenges: Our moderate-to-hot summers, combined with low humidity and dry-summer rainfall, can stress geraniums if you're not careful with watering. Be especially vigilant about monitoring soil moisture and providing adequate water during heat waves. The good news is that geraniums tolerate heat better than many other flowering plants, so with a little attention, they'll thrive in your NorCal garden.

Geraniums make good companions for several plants in the Northern California garden. They are often planted near tomatoes and peppers because their scent is said to deter certain pests, like tomato hornworms and aphids. Corn also benefits from geraniums as they can attract beneficial insects that prey on corn earworms.

Roses also benefit from geraniums planted nearby, as they can deter Japanese beetles. Avoid planting geraniums near fennel, as it can inhibit their growth.