When to Plant Radishes in New Hampshire (2026 Guide)

Radishes are an excellent choice for New Hampshire gardeners looking for fast-growing vegetables. Known for their rapid maturation, some varieties can go from seed to harvest in as little as 22 days. With the state's varied climate, understanding when to plant your radishes is crucial to ensuring a bountiful harvest. For gardeners in Zone 5b, the median last spring frost date is May 11, while those in Zone 6a enjoy a slightly earlier date, April 28, making these dates important benchmarks.

Planting radishes in New Hampshire also requires careful planning around frost dates. The first fall frost typically occurs around September 30 in Zone 5b and October 9 in Zone 6a, giving gardeners in both zones ample time to enjoy multiple harvests. As you consider planting radishes, it's essential to note their suitability as companion plants, making them ideal for both novice and experienced gardeners alike.

Whether you're in bustling cities like Manchester or Nashua, there's a wealth of opportunity when it comes to growing radishes. With limited growing seasons, timing becomes paramount. This guide will help you navigate the complexities of planting radishes, addressing common mistakes and providing companion planting advice tailored for New Hampshire's unique gardening landscape.

Planting Schedule by USDA Zone in New Hampshire

Zone	Indoor start	Transplant out	Direct sow	Harvest
Zone 5b	Not recommended — direct sow only	Not recommended — direct sow only	Start April 15 – May 1, ~2–4 weeks after May 11	Harvest from May 25 – July 15
Zone 6a	Not recommended — direct sow only	Not recommended — direct sow only	Start April 1 – April 15, ~2–4 weeks after April 28	Harvest from May 20 – July 15

Radishes Planting Windows in New Hampshire

Indoor start: Radishes do not require an indoor start in New Hampshire; they are best direct sown from mid to late April.
Transplant outdoors: Radishes should only be direct sown starting from April 1 in Zone 6a and April 15 in Zone 5b.
Harvest: Expect to harvest radishes between May 20 and July 15, depending on the variety planted and the planting time.

Common Mistakes Growing Radishes in New Hampshire

One common mistake in New Hampshire is planting radishes too close to the frost date. Gardners often want to get an early start, but planting too close to late frosts can spoil your crop. Remember that radishes need at least a few weeks after the last frost to grow properly.
Many gardeners in New Hampshire forget about the importance of thin planting. Crowding radishes can prevent proper root formation, leading to small, woody, and inedible crops. Thinning to 2–3 inches apart is essential for healthy growth.
Due to the humid conditions in parts of New Hampshire, some gardeners plant their radishes and forget about the watering needs. While radishes require moisture, excessive humidity can lead to fungal diseases, stunting growth. Regular, careful monitoring helps maintain optimal conditions.
Another mistake is misjudging the harvest timing. Radishes that are left in the ground too long can become pithy and overly hot. It's essential to be vigilant and harvest promptly once they reach maturity, which is typically around 25-30 days.
Gardeners often overlook the benefit of succession planting. In New Hampshire, where the growing season can be short, planting radishes every 1-2 weeks ensures a continuous supply. Skipping this can lead to gaps in your vegetable production, leaving you without fresh radishes for longer periods.

Frequently Asked Questions

What should I do if I live in a colder part of New Hampshire?

If you're in a colder region, consider delaying your planting until you're certain there won’t be any late frosts. Use a soil thermometer to monitor conditions and ensure that the soil has warmed adequately before sowing your radish seeds.

Can I still plant radishes in May?

Yes, May is a great time to plant radishes in New Hampshire, especially in Zone 5b after May 11. Just be sure to monitor the weather for any unexpected cold snaps and plant accordingly for a successful crop.

How often should I water my radishes?

Radishes prefer consistent moisture, so aim to water them regularly, especially during dry spells. However, be careful not to overwater, as too much moisture can lead to diseases. Aim for an inch of water per week, adjusting based on rain.

What if my radishes are too spicy?

If your radishes are turning out too spicy, they may be overmature or stressed due to lack of water. Ensure you’re harvesting them promptly and providing adequate moisture throughout their growing period to keep the flavor mild.

Are radishes suitable for intercropping?

Absolutely! Radishes make great intercropping companions since they grow quickly and can be harvested before other crops need the space. This technique can maximize the use of your garden bed and improve overall efficiency.

Keep Learning

Typical fall sowing window for Radishes in New Hampshire: August 4 – August 25.