New Hampshire’s cold winters demand patience, as geraniums cannot go outside until late May. Knowing the best time to plant geranium in New Hampshire means waiting for the last frost to pass and the soil to warm up.
Geraniums are not frost-hardy plants. If you put them out too early, a single cold night can kill them. In New Hampshire, the safe window usually opens in late May, but it depends on your specific zone.
Best Time To Plant Geranium In New Hampshire
The ideal planting window for geraniums in New Hampshire is from late May to early June. This timing ensures the soil has warmed to at least 60°F and the risk of frost has passed. In southern parts of the state, you might plant as early as mid-May. In northern areas, wait until early June.
Check your local frost dates. The average last frost in Concord is around May 15, but in Berlin it can be as late as May 30. Always watch the weather forecast before planting.
Understanding New Hampshire’s Growing Zones
New Hampshire spans USDA hardiness zones 3b to 6a. This affects when you can safely plant geraniums.
- Zone 3b-4a (Northern NH): Last frost typically late May to early June. Plant geraniums around June 1.
- Zone 4b-5a (Central NH): Last frost around mid to late May. Plant around May 20-25.
- Zone 5b-6a (Southern NH): Last frost in early to mid-May. Plant around May 15-20.
These dates are averages. A cold snap can happen anytime in spring. Always have row covers or cloths ready to protect your plants if frost is predicted.
Why Timing Matters So Much
Geraniums are tropical plants native to South Africa. They cannot handle freezing temperatures. Even a light frost at 32°F will damage leaves and stems. Cold soil also slows root growth and can cause rot.
Planting too late is also a problem. Geraniums need at least 6-8 weeks of warm weather to bloom well before fall frosts arrive. In New Hampshire, the first fall frost can come as early as mid-September in the north. So you have a limited growing season.
By planting in late May or early June, you give your geraniums the best chance to establish roots and produce flowers all summer long.
Preparing Your Geraniums For Planting
Before you put geraniums in the ground, you need to harden them off. This is a critical step that many gardeners skip.
Hardening Off Process
If you started geraniums indoors or bought them from a greenhouse, they are used to warm, protected conditions. Sudden exposure to wind, sun, and cold can shock them.
- Start about 7-10 days before your planned planting date.
- Place geraniums outside in a shaded, sheltered spot for 2-3 hours on the first day.
- Increase outdoor time by 1-2 hours each day.
- Gradually move them into more direct sunlight over the week.
- Bring them indoors at night if temperatures drop below 50°F.
- After 7-10 days, they should be ready for full sun and overnight stays.
This slow acclimation reduces transplant shock and helps your geraniums thrive.
Soil Preparation
Geraniums prefer well-draining soil with a pH between 6.0 and 7.0. In New Hampshire, many gardens have acidic soil from pine needles and rainfall. Test your soil pH before planting.
If your soil is too acidic, add lime to raise the pH. If it is heavy clay, mix in compost or aged manure to improve drainage. Geranium roots rot easily in soggy soil.
Work the soil to a depth of 8-10 inches. Remove rocks and weeds. Add a balanced fertilizer like 10-10-10 at planting time.
Choosing The Right Geranium Varieties
Not all geraniums are the same. For New Hampshire’s short growing season, choose varieties that bloom quickly and tolerate cool nights.
- Zonal geraniums: Most common type. Bloom from June until frost. Good for beds and containers.
- Ivy geraniums: Trailing habit, great for hanging baskets. Need more heat, so plant in full sun.
- Regal geraniums: Also called Martha Washington. Bloom early but stop in heat. Best for spring and early summer.
- Scented geraniums: Grown for leaves, not flowers. More cold-tolerant but still need frost-free conditions.
For northern New Hampshire, zonal geraniums are the most reliable choice. They handle cooler nights better than ivy types.
How To Plant Geraniums Step By Step
Once the soil is warm and your plants are hardened off, follow these steps for successful planting.
Step 1: Choose The Right Location
Geraniums need at least 6 hours of direct sunlight daily. Morning sun is best because it dries dew quickly and prevents disease. In southern NH, some afternoon shade can help during heat waves.
Good air circulation is also important. Avoid planting too close to walls or fences where air gets trapped. This reduces the risk of fungal diseases.
Step 2: Space Plants Properly
Give geraniums room to grow. Space them 12-18 inches apart for garden beds. For containers, use one plant per 10-inch pot or three plants in a 14-inch pot.
Crowded plants compete for water and nutrients. They also get less airflow, which encourages powdery mildew.
Step 3: Dig The Hole
Dig a hole twice as wide as the root ball but no deeper. The top of the root ball should be level with the soil surface. Planting too deep can cause stem rot.
Gently loosen the roots if they are circling the pot. This encourages them to spread into the surrounding soil.
Step 4: Backfill And Water
Fill the hole with soil, pressing gently to remove air pockets. Water thoroughly right after planting. This settles the soil and hydrates the roots.
Add a 2-inch layer of mulch around the plant, but keep it away from the stem. Mulch helps retain moisture and keeps soil temperature stable.
Step 5: Water Regularly
After planting, water geraniums deeply once a week if there is no rain. In hot weather, they may need water every 2-3 days. Always water at the base to keep leaves dry.
Check soil moisture by sticking your finger 1 inch into the soil. If it feels dry, it’s time to water. Overwatering is a common mistake that leads to yellow leaves and root rot.
Caring For Geraniums Through The Season
Once planted, geraniums need consistent care to bloom from June until frost.
Fertilizing
Feed geraniums every 2-4 weeks with a balanced liquid fertilizer. Use a formula like 20-20-20 diluted to half strength. Too much nitrogen produces lots of leaves but few flowers.
Stop fertilizing in late August to help plants slow down before fall.
Deadheading
Remove spent flowers regularly. This encourages the plant to produce more blooms instead of seeds. Snip off the entire flower stem at the base.
Also remove yellow or dead leaves to keep the plant tidy and reduce disease risk.
Pest And Disease Control
Common pests in New Hampshire include aphids, whiteflies, and spider mites. Check undersides of leaves weekly. If you see pests, spray with insecticidal soap or neem oil.
Fungal diseases like botrytis and rust can occur in humid weather. Avoid overhead watering and ensure good air circulation. Remove infected leaves immediately.
Preparing For Fall
In early September, start watching for frost warnings. Geraniums can tolerate light frost if covered, but heavy frost kills them.
If you want to save geraniums for next year, dig them up before the first hard frost. Pot them and bring indoors. Place in a sunny window or a cool, dark basement for dormancy.
Container Planting Tips
Many New Hampshire gardeners grow geraniums in pots and hanging baskets. Containers warm up faster than ground soil, so you can plant a bit earlier.
Use pots with drainage holes. Fill with high-quality potting mix, not garden soil. Add slow-release fertilizer at planting time.
Containers dry out faster than garden beds. Check soil daily in hot weather. Water until it runs out the bottom.
For winter, move containers to a protected area like a garage or basement. Geraniums can survive as houseplants if given enough light.
Common Mistakes To Avoid
Even experienced gardeners make errors with geraniums. Here are the most common ones in New Hampshire.
- Planting too early: The biggest mistake. Wait until frost danger is completely gone.
- Overwatering: Geraniums prefer to dry out between waterings. Wet soil leads to root rot.
- Too much shade: Geraniums need full sun to bloom well. Less than 6 hours of sun results in leggy plants with few flowers.
- Skipping hardening off: Indoor plants need time to adjust. Shock can stunt growth for weeks.
- Ignoring soil pH: Acidic soil prevents nutrient uptake. Test and amend as needed.
Frequently Asked Questions
Can I plant geraniums in New Hampshire in April?
No, April is too early. The soil is still cold and frost is likely. Wait until at least mid-May in southern NH and early June in the north.
What is the latest time to plant geraniums in New Hampshire?
You can plant geraniums as late as mid-July, but they may not have enough time to bloom before fall frost. For best results, plant by early June.
Do geraniums come back every year in New Hampshire?
No, geraniums are tender perennials that cannot survive New Hampshire winters outdoors. They are grown as annuals or overwintered indoors.
Should I start geraniums from seed or buy plants?
Starting from seed takes 12-16 weeks indoors before planting out. Most gardeners in NH buy started plants from nurseries for easier timing.
How do I protect geraniums from late frost?
Cover plants with frost cloth, old sheets, or plastic containers overnight. Remove covers in the morning when temperatures rise above freezing.
Final Thoughts On Planting Geraniums In New Hampshire
Timing is everything for geraniums in this state. The best time to plant geranium in New Hampshire is late May to early June, after the last frost and when soil is warm. Prepare your plants with hardening off, choose the right variety, and provide consistent care through the season.
With proper timing and care, your geraniums will reward you with vibrant blooms from summer through early fall. Enjoy the color they bring to your New Hampshire garden.