Oklahoma’s variable spring weather means nasturtium should be planted after the last frost, typically in April, to avoid cold damage. The best time to plant nasturtium in oklahoma is a question many gardeners ask, and the answer depends on your specific region within the state. Getting the timing right ensures vibrant blooms and healthy leaves all summer long.
Nasturtiums are surprisingly tough, but they hate frost. A late freeze can kill young seedlings instantly. That is why waiting until the soil warms up is so important.
In this guide, you will learn exactly when to plant nasturtium seeds or transplants in Oklahoma. We will cover soil temperature, frost dates, and even tips for fall planting.
Best Time To Plant Nasturtium In Oklahoma
The ideal window for planting nasturtiums in Oklahoma is from mid-April to early May. This timing works for most of the state, from Tulsa to Oklahoma City to Lawton. However, you must check your local frost date first.
Nasturtiums are annuals in Oklahoma. They complete their life cycle in one season. Planting them too early risks frost damage. Planting them too late means less time to bloom before the summer heat arrives.
Understanding Oklahoma’s Last Frost Dates
Oklahoma has three main climate zones. The last frost date varies by about two weeks across the state.
- Northern Oklahoma (Panhandle, Enid, Ponca City): Last frost typically occurs around April 15–20. Plant nasturtiums after this date.
- Central Oklahoma (Oklahoma City, Norman, Stillwater): Last frost is usually around April 5–10. You can plant in mid-April.
- Southern Oklahoma (Ardmore, Durant, Lawton): Last frost often happens by March 25–30. Early April planting is safe here.
Always check your local weather forecast before planting. A late cold snap can happen even in late April. If frost is predicted, cover young plants with a cloth or bring containers indoors.
Soil Temperature Matters More Than Air Temperature
Nasturtium seeds need warm soil to germinate. The soil temperature should be at least 55°F (13°C) for seeds to sprout. Ideally, aim for 60–70°F.
You can check soil temperature with a simple soil thermometer. Insert it two inches deep in the morning. If the reading is below 55°F, wait another week.
In Oklahoma, soil usually reaches 55°F by mid-April in most areas. In northern regions, it may take until late April. Planting in cold, wet soil can cause seeds to rot.
Planting Nasturtium Seeds Directly In The Ground
Direct sowing is the easiest method for nasturtiums. They have delicate roots that do not transplant well. Follow these steps for success.
- Prepare the soil: Choose a spot with full sun to partial shade. Nasturtiums prefer poor to average soil. Do not add too much compost or fertilizer. Rich soil produces more leaves and fewer flowers.
- Soak the seeds overnight: Nasturtium seeds have a hard outer coat. Soaking them in warm water for 12–24 hours helps speed up germination. Drain them before planting.
- Plant seeds ½ to 1 inch deep: Space seeds about 10–12 inches apart. For bush varieties, you can plant them closer. For trailing types, give them more room.
- Water gently: Keep the soil moist but not waterlogged. Seeds should sprout in 7–14 days if the soil is warm enough.
- Thin seedlings if needed: Once seedlings have two sets of true leaves, thin them to one plant every 10–12 inches.
Direct sowing works best from mid-April to early May. If you miss this window, you can still plant seeds until June. They will bloom later in summer but still produce flowers.
Starting Nasturtium Seeds Indoors
Starting seeds indoors gives you a head start. You can transplant seedlings after the last frost. However, nasturtiums do not like root disturbance. Use biodegradable pots that can be planted directly into the ground.
- Start seeds 4–6 weeks before the last frost: For central Oklahoma, that means starting seeds in early March. For northern areas, start in late March.
- Use peat pots or paper pots: These pots break down in the soil. This prevents root damage during transplanting.
- Plant one seed per pot: Place the seed ½ inch deep. Keep the soil moist and warm (70°F).
- Provide bright light: Place pots in a sunny window or under grow lights. Seedlings need 12–16 hours of light daily.
- Harden off before transplanting: About a week before planting, move seedlings outdoors for a few hours each day. Gradually increase their time outside.
- Transplant after the last frost: Dig a hole the same size as the pot. Place the entire pot in the ground. Water well.
Indoor starting is optional. Most Oklahoma gardeners find direct sowing easier and more reliable for nasturtiums.
Planting Nasturtium Transplants From Nurseries
If you buy nasturtium plants from a garden center, you can plant them after the last frost. Look for healthy, compact plants with no yellow leaves. Avoid plants that are leggy or root-bound.
Transplants should be planted at the same depth they were in the pot. Space them 10–12 inches apart. Water them well after planting. They may wilt for a day or two but should recover quickly.
Nursery transplants are a good option if you missed the seed-planting window. You can find them from April through June in Oklahoma.
Fall Planting For Nasturtiums In Oklahoma
Nasturtiums can also be planted in late summer for a fall bloom. The best time for fall planting is from late August to early September. This gives plants time to grow before the first frost.
Oklahoma’s first frost usually occurs in October or November. In northern areas, it can happen as early as mid-October. In southern areas, it may be early November.
Fall-planted nasturtiums will bloom until the first hard freeze. They often have fewer pests in cooler weather. Plant them in a spot that gets afternoon shade to protect them from late-summer heat.
Follow the same planting steps as for spring. Soak seeds, plant them ½ inch deep, and water regularly. Fall planting is a great way to extend your gardening season.
Best Locations For Nasturtiums In Oklahoma
Nasturtiums grow well in many parts of Oklahoma. They thrive in full sun but appreciate some afternoon shade in hot summers. In southern Oklahoma, partial shade is often better.
Choose a location with well-draining soil. Nasturtiums do not like wet feet. If your soil is heavy clay, consider planting them in raised beds or containers.
Containers are a great option for Oklahoma gardeners. You can move them to protect from frost or extreme heat. Use a pot with drainage holes and fill it with a light potting mix.
Companion Planting With Nasturtiums
Nasturtiums are excellent companion plants. They repel aphids, whiteflies, and squash bugs. Many Oklahoma gardeners plant them near vegetables like tomatoes, cucumbers, and squash.
They also attract beneficial insects like ladybugs and hoverflies. These insects help control pests naturally. Plant nasturtiums along the edges of your vegetable garden for best results.
Avoid planting nasturtiums near beans or peas. They can compete for nutrients. Otherwise, they are friendly neighbors to most garden plants.
Caring For Nasturtiums After Planting
Nasturtiums are low-maintenance plants. They need very little care once established. Here are a few tips to keep them healthy.
- Water sparingly: Nasturtiums prefer dry conditions. Water only when the soil feels dry an inch below the surface. Overwatering can cause root rot.
- Do not fertilize: These plants bloom best in poor soil. Fertilizer encourages leaf growth at the expense of flowers. Skip the plant food.
- Deadhead spent blooms: Removing faded flowers encourages more blooms. You can also let them go to seed for next year.
- Watch for pests: Aphids sometimes attack nasturtiums. A strong spray of water from a hose can knock them off. Avoid using chemical pesticides.
Nasturtiums are drought-tolerant once established. In Oklahoma’s hot summers, they may need water every few days. Check the soil regularly.
Common Problems With Nasturtiums In Oklahoma
Even though nasturtiums are easy to grow, a few issues can arise. Here are the most common problems and how to fix them.
Yellow Leaves
Yellow leaves often mean overwatering or poor drainage. Let the soil dry out between waterings. If the plant is in a container, make sure it has drainage holes.
Few Flowers, Lots Of Leaves
This usually happens when the soil is too rich. Nasturtiums bloom best in lean soil. Do not add compost or fertilizer. If you already did, next year plant them in a different spot.
Leggy Growth
Leggy plants are often caused by too much shade. Move them to a sunnier location. They need at least 6 hours of direct sunlight daily.
Pests
Aphids are the most common pest. They are attracted to nasturtiums. A strong water spray usually works. If not, use insecticidal soap. Avoid neem oil as it can harm beneficial insects.
Harvesting Nasturtium Flowers And Leaves
Nasturtiums are edible. Both flowers and leaves have a peppery flavor similar to watercress. You can add them to salads, sandwiches, or use as a garnish.
Harvest flowers when they are fully open. Pick them in the morning for the best flavor. Leaves can be picked at any size. Young leaves are milder.
Rinse them gently before eating. Nasturtiums are safe to eat, but avoid using any that have been treated with pesticides. If you buy plants from a nursery, ask if they are edible.
Store harvested flowers and leaves in a plastic bag in the refrigerator. They will stay fresh for up to three days.
Saving Nasturtium Seeds For Next Year
Nasturtiums produce large seeds that are easy to save. Let some flowers go to seed at the end of the season. The seeds will turn brown and fall off the plant.
Collect the seeds and spread them on a paper towel to dry for a week. Store them in a paper envelope in a cool, dry place. They will remain viable for 3–5 years.
In Oklahoma, you can also let nasturtiums self-seed. Some seeds will survive the winter and sprout the next spring. This works best in mild winters.
Frequently Asked Questions
Can I plant nasturtium seeds in July in Oklahoma?
Yes, but they will bloom later in summer. Plant them in early July for fall flowers. Water them regularly during hot weather.
Do nasturtiums need full sun in Oklahoma?
They prefer full sun but tolerate partial shade. In southern Oklahoma, afternoon shade helps them survive summer heat.
How deep should I plant nasturtium seeds?
Plant seeds ½ to 1 inch deep. Deeper planting can prevent germination.
Can I grow nasturtiums in pots in Oklahoma?
Yes, containers work well. Use a pot with drainage holes and light potting mix. Move them to shade during heat waves.
Will nasturtiums survive Oklahoma’s hot summers?
They are heat-tolerant but may slow down in extreme heat. Provide afternoon shade and regular water to keep them blooming.
Final Tips For Oklahoma Gardeners
Timing is everything for nasturtiums in Oklahoma. Wait until the soil warms up and the last frost has passed. Mid-April to early May is your safest bet.
If you are unsure about your local frost date, ask a neighbor or check with your county extension office. They have local gardening advice tailored to your area.
Nasturtiums are forgiving plants. Even if you plant them a little late, they will still reward you with colorful blooms. Just avoid planting them in cold, wet soil.
Remember to soak seeds overnight for faster germination. Plant them in poor soil and water sparingly. With minimal care, you will have beautiful nasturtiums all season long.
Oklahoma’s weather can be unpredictable, but with the right timing, nasturtiums thrive here. Enjoy their bright flowers and peppery leaves in your garden this year.