Geranium in Zone 8A — Northern California

Geraniums are a classic choice for Northern California gardens, offering vibrant color and a delightful fragrance that can elevate any outdoor space. They’re incredibly versatile, working well in containers, borders, or even as ground cover, and their cheerful blooms make them a rewarding addition to your garden. Plus, they attract pollinators, contributing to a healthy garden ecosystem.

Our Mediterranean climate, with its long, dry summers and mild winters, presents some unique challenges, but don't worry. With a bit of planning and attention to watering, you can successfully grow geraniums. Our long 255-day growing season gives you plenty of time to enjoy their beauty.

Starting geraniums from seed indoors is possible, but it's honestly a slow process. You'll get a head start, but most of us NorCal gardeners find it easier to buy established plants from a local nursery. If you're up for the challenge, though:

Begin starting your geranium seeds indoors from late December through mid January. This gives them about 12 weeks to develop before transplanting. Use seed trays with a good seed-starting mix, providing warmth and bright light – a grow light really helps, especially with our early spring character.

A good tip is to water your seedlings from the bottom by placing the seed tray in a shallow dish of water. This encourages strong root growth and prevents damping-off. Just make sure you don't let them sit in water for too long.

Transplanting geraniums outdoors should be done from late March through late April, after the last expected frost. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind, preventing transplant shock.

Space your geraniums about 10-12 inches apart to allow for good air circulation. Keep an eye on the weather forecast around transplant time. We can still get some unexpected chilly nights in early spring, so be prepared to cover your young plants if needed. As I mentioned before, geraniums are very slow from seed, so buying starts is the easiest way to get instant color in your garden.

Geraniums need moderate watering, but they definitely don't like soggy soil. In our Northern California climate, especially with those dry summers, it's important to find the right balance. Let the soil dry out slightly between waterings to prevent stem rot, which is a common problem.

During the cooler spring months, you might only need to water once a week, or even less if we get some rain. As the weather heats up in the summer, increase your watering to 2-3 times a week, depending on how quickly the soil dries out. Use the "finger test": stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. Aim for about 1 inch of water per week, adjusting based on rainfall and temperature.

Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our low-humidity environment. Signs of underwatering include wilting leaves and dry, crispy edges. Overwatering, on the other hand, can lead to yellowing leaves and mushy stems. Applying a layer of mulch around your geraniums helps retain moisture in the soil and suppress weeds, which is especially helpful during our dry summers.

Pruning geraniums is essential for keeping them looking their best and encouraging continuous blooming. The main type of pruning you'll be doing is deadheading.

Throughout the growing season, from spring through fall, regularly remove spent flower clusters by snipping them off just above a leaf node. This prevents the plant from putting energy into seed production and encourages it to produce more flowers. If your geraniums start to look leggy, pinch back the stems to encourage bushier growth. As our first frost approaches around mid- November, you can give your geraniums a final trim to tidy them up before winter. You can also bring them indoors to overwinter them.

While you won't be "harvesting" geraniums for food, you will be harvesting their beauty all season long! Expect your geraniums to start blooming in early June and continue through late July.

The best way to "harvest" is to simply enjoy their flowers in your garden. Regularly remove faded blooms to keep the plants looking neat and encourage continued flowering. Cut the spent flower stalks just above a leaf node to promote new growth.

As our first frost approaches in mid- November, you can take cuttings from your geraniums to propagate new plants indoors over the winter. This is a great way to preserve your favorite varieties and get a head start on next year's garden.

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

Botrytis Blight

• What it looks like: Gray mold on leaves, stems, and flowers, often starting as small, water-soaked spots.
• What causes it: High humidity and poor air circulation, which can occur during our wetter spring months or in overly crowded plantings.
• How to fix/prevent it: Improve air circulation by spacing plants properly and pruning out crowded growth. Remove and destroy any affected plant parts. Avoid overhead watering, and consider using a fungicide if the problem is severe.

Geranium Budworm

• What it looks like: Small holes in buds and flowers, often with dark droppings nearby. You might also find small green or brown caterpillars feeding on the plant.
• What causes it: These caterpillars are the larvae of moths that lay their eggs on geraniums.
• How to fix/prevent it: Inspect your plants regularly for signs of budworms. Handpick any caterpillars you find. You can also use Bacillus thuringiensis (Bt), a biological insecticide that is effective against caterpillars.

Edema

• What it looks like: Small, blister-like bumps on the undersides of leaves, which can turn brown and corky over time.
• What causes it: Edema is caused by inconsistent watering and high soil moisture. This can happen during periods of heavy rain followed by warm weather.
• How to fix/prevent it: Improve drainage in your soil. Avoid overwatering, and allow the soil to dry out slightly between waterings. Ensure good air circulation around your plants.

Northern California Specific Challenges: Our dry summers can stress geraniums if they're not watered properly, making them more susceptible to pests and diseases. Also, our intense sun can scorch the leaves if plants are not acclimated properly or if they're planted in a location that gets too much direct sun. Providing adequate water, mulching to retain moisture, and choosing a location with partial shade can help your geraniums thrive in our unique climate.

Geraniums make excellent companions for several plants in the Northern California garden.

Tomatoes and peppers benefit from being planted near geraniums because geraniums can repel certain pests that commonly attack these vegetables, such as tomato hornworms. Corn also enjoys the pest-repelling qualities of geraniums.

Roses are another great companion for geraniums. Geraniums help deter Japanese beetles, which can be a major problem for roses in our area.

Avoid planting geraniums near fennel, as fennel can inhibit the growth of many plants, including geraniums.