Geranium in Zone 4B — Northeast

Geraniums are a welcome splash of color in our Northeast gardens. Their vibrant blooms brighten up borders and containers, and they're surprisingly resilient, tolerating the moderate heat we often get during our short summers. Plus, those cool nights we're known for seem to intensify their colors.

Our short growing season and the occasional late spring or early fall frost can be a concern, but starting geraniums indoors or buying established plants makes it entirely manageable. With a little planning within our 138-day growing season, you can enjoy geranium blooms from summer well into fall.

Starting geraniums from seed indoors is possible, but be warned: they're notoriously slow growers. If you’re eager to get a head start, begin in late February through mid March, about 12 weeks before you plan to move them outside. It's a longer commitment than many other flowers.

Use seed trays filled with a good seed-starting mix, and provide consistent warmth and bright light. Bottom watering is a great way to keep the soil moist without overwatering, which can lead to problems. Given our late springs here in the Northeast, indoor starting gives you a jump, but many gardeners find buying established plants is an easier route to success.

Transplant your geraniums outdoors in late May through late June, once the danger of frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Northeast's variable spring weather.

Space the plants 10-12 inches apart to allow for good air circulation. Keep in mind that even in late May, we can still get a surprise cold snap here, so be prepared to cover your young plants if necessary. Given how slow geraniums are from seed, many of us in Zone 4B just buy starts from the local garden center for a quicker show of color.

Geraniums need moderate watering, and it's crucial to let the soil dry slightly between waterings. Overwatering is a common mistake that can lead to stem rot. They're tougher than some other flowers when it comes to heat, but they still need consistent moisture.

During the summer months, check the soil moisture regularly – the "finger test" works well. 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, either from rainfall or supplemental watering. Given our moderate-to-humid conditions in the Northeast, it's best to water at the base of the plant to avoid getting the foliage too wet.

Signs of underwatering include wilting leaves and dry, cracked soil. Overwatering, on the other hand, can cause yellowing leaves and soft, mushy stems. Mulching around your geraniums with a layer of compost or shredded bark helps retain moisture and keeps the soil temperature consistent, which is especially helpful during our fluctuating summer weather.

Deadheading is essential for keeping your geraniums blooming throughout the season. Simply pinch or snip off the spent flower clusters as soon as they start to fade. This encourages the plant to produce more blooms instead of putting energy into seed production.

Throughout the summer, you can also pinch back any leggy stems to encourage bushier growth. As we approach late September and the threat of our first frost looms, stop deadheading. Let the plant focus on hardening off rather than producing new growth that will likely be damaged by the cold.

While you won't be harvesting geraniums for food, you'll be "harvesting" their beauty from early August through mid September. The plants will be producing flowers throughout the summer, so your main goal is to maintain their appearance and encourage continued blooming.

The best sign that it's time to "harvest" is when the flowers begin to fade. Remove the faded blooms promptly to keep the plant looking tidy and to prevent it from wasting energy on seed production. Cut the flower stem back to a leaf node to encourage new growth.

As the first frost approaches in late September, enjoy the last of the blooms. There's no need to harvest anything specific before the frost; just let the plants fade naturally as the temperatures drop. You can then remove the plants from your garden and compost them.

Here are some common problems you might encounter with geraniums in the Northeast:

Botrytis Blight

• What it looks like: Grayish-brown mold on flowers, leaves, and stems, often starting on damaged or fading parts of the plant.
• What causes it: High humidity and cool temperatures create ideal conditions for this fungal disease. Our moderate-to-humid summers can definitely contribute.
• How to fix/prevent it: Improve air circulation by spacing plants properly and pruning out crowded growth. Remove infected plant parts immediately. Avoid overhead watering, especially in the evening. Fungicides can be used in severe cases, but prevention is key.

Geranium Budworm

• What it looks like: Small holes in flower buds and petals. You might also see small, green caterpillars inside the buds.
• What causes it: These caterpillars feed on the developing flower buds, causing damage and preventing the flowers from opening properly.
• How to fix/prevent it: Inspect plants regularly for signs of infestation. Handpick caterpillars when possible. Bacillus thuringiensis (Bt) is an effective organic treatment.

Edema

• What it looks like: Small, blister-like bumps on the undersides of leaves. These bumps can turn brown and corky over time.
• What causes it: Edema is caused by excessive moisture in the soil combined with cool temperatures and high humidity. This condition is more common during periods of prolonged rain or when plants are overwatered.
• How to fix/prevent it: Improve drainage in the soil. Avoid overwatering, especially during cool, cloudy weather. Provide good air circulation around the plants.

Northeast Specific Challenges: Our moderate heat, moderate-to-humid humidity, and even rainfall can create favorable conditions for fungal diseases like botrytis blight. Be vigilant about monitoring your plants and taking preventative measures to avoid these problems.

Geraniums make good companions for several plants in the Northeast garden:

• Tomatoes: Geraniums are thought to repel certain pests that attack tomatoes, such as tomato hornworms.
• Peppers: Similar to tomatoes, geraniums can help deter pests that might bother peppers.
• Corn: Geraniums may help to deter corn earworms, though the effect is not as pronounced as with tomatoes and peppers.
• Roses: Geraniums are often planted near roses to deter Japanese beetles, which can be a significant pest in our region.

There aren't any specific plants that are known to be bad companions for geraniums. However, avoid planting them too close to plants that require very different watering needs, as this could lead to overwatering or underwatering issues.