Updated: Sep 15, 2022
This root vegetable has been around since pre-Roman times. It’s got a fairly distinct peppery taste and is packed with lots of great nutrients. Radishes make for a crunchy addition to salads, but are also tasty when roasted, pickled, and thrown in tacos.
To help ensure your Radishes thrives, we’ve put together this how-to video and transcript, covering topics like:
Varieties of Radishes available
Caring for Radishes at all stages
Fertilizer and Mulching
Transplanting best practices
Radish Companion Plants
Pests, Diseases and what to do about them
Harvesting and storing your Radishes
Listen to this Article:
Glossary of radish terms
Before we get started, let’s learn a little bit about radishes.
The premature production of a flowering stem (or stems) on a plant before it can be harvested. Bolting is the plant’s natural attempt to produce seeds for reproduction. Typically, radishes bolt because of high temperatures, and those that do bolt will have a bitter, undesirable flavor with a woody texture.
The process of growing plants close together because of their ability to enhance each other’s growth or flavor.
A process that’s needed for a radish to produce seeds. Radish flowers are pollinated by insects like bees and flies, with honeybees being the most important radish pollinators.
A form of companion planting, using a crop that attracts agricultural pests (like bugs) away from your main crops.
Varieties of radish
If you like having options, you’ll love radishes – they have so many different varieties for you to choose from.
EARLY SCARLET GLOBE
This globe-shaped, bright red variety has a small taproot and takes 23 days to harvest.
Similar Varieties: Fuego 25 days; This variety is round, red, and have medium tops. They’re resistant to fusarium, and tolerant to blackroot/black scurf.
A rounded, deep magenta variety that’s large in shape and can be harvested after 25 days.
A smooth, white, and round variety that’s ready for harvest after 30 days.
This variety has more of an oblong shape – it’s red near the top with a white tip, and takes 23 days to be harvest-ready.
A long, white, tapered variety that takes 25 days to become harvest-ready.
Rose-colored on the outside, white on the inside, and takes 52 days for harvest.
This variety is quite large and fairly long, with square “shoulders” and blunt tips. Its roots are creamy white, and it takes 60 days to become harvest-ready.
Similar Varieties: Tama Hybrid This is a daikon type of radish, taking 70 days for harvest. Its roots can get as long as 18 inches, with a 3 inch diameter. They’re smooth, white, and have a blunt tip.
ROUND BLACK SPANISH
This type has a distinctly rough and black skin, white flesh, and takes 55 days to harvest.
Starting your radish seeds
Radishes are always grown from seed, then directly planted so as not to disturb their roots. Seeds germinate best at 55-75°F (13 – 24°C) and need about 5-10 days to emerge. Also, their soil pH should be 6.5 or higher.
Prepare your garden bed by loosening the soil at least six inches deep (a foot or more for long types). For daikon varieties, create raised beds to ensure there’s enough loosening of the soil. It’ll also make your harvest much easier.
Radishes grow best in rich, loamy soil that’s been amended with composted manure. You’ll want to add 1 cup of a complete organic fertilizer for every 10 feet (3 m) of row.
Allow about one inch between seeds in the row.
Plant seeds from smaller varieties shallowly, about a quarter to a half inch deep. If you’re growing a bigger variety, you can sow their seeds up to one inch deep.
Heavy rains or excessive watering can cause soil crusting, which may weaken your seedlings’ emergence.
If your soil surface has crusted, you’ll want to lightly sprinkle it with water to moisten and soften the crust.
Thin your radishes to about two inches between plants as soon as they reach a small, edible size.
For larger varieties (like daikons), allow 4-6 inches between plants. Make sure to also pull any weeds from the row when you thin your radishes.
Keep in mind that although sunlight is needed for radish seeds to grow, it’s not needed for them to germinate.
Caring for radishes
We’ll tell you everything you need to know about caring for your radishes, from watering and weeding, to fertilizer and mulching.
We’ll also explain which crops grow best with radishes, and what structures you can use.
Radishes are pretty low maintenance, needing little care after planting. One thing they do need, though, is a consistent and sufficient supply of water.
Drought stress can cause their roots to develop poor flavor and a tough texture, so if your radishes don’t get an inch of rain each week, soak the soil thoroughly at least once a week to keep them nice and watered.
Thin your radishes shortly after your seedlings emerge. Radishes are quick growers, so they need 1.5 inches of space between them for quick root growth.
Bonus: any thinned leaves or roots can be eaten in salads.
Weeds should be removed carefully from around your radish plants, because they do no compete well.
Weed control is especially important during and just after germination, when your radish plants are growing slowly.
You’ll want to avoid deep cultivation around your plants though, since root pruning and damage will affect their growth and yield.
Also, be sure to rotate their planting location in your garden from year to year to help control the spread of diseases.
FERTILIZING AND/OR MULCHING
By adding nitrogen fertilizer or nitrogen rich organic manure (chicken coop manure, alfalfa pellets, compost tea, fish fertilizer, etc.,) close to your radish plants, it will help them to produce lush tops and small roots.
You can apply a quarter cup of a nitrogen-based fertilizer (21-0-0) for each 10 foot of row.
You’ll want to apply it about 3-4 weeks after your seedlings emerge to encourage them to grow quickly. Simply place the fertilizer to the side of your plants, then water it into your soil.
Mulching with 3-4 inches of herbicide-free grass clippings, weed-free straw, compost, or other organic material will keep your soil’s moisture while containing weeds, which means you won’t need to cultivate as often.
COMPANION PLANTS DO’S AND DON’TS
Plant your radishes near beans, beets, celeriac, chervil, lettuce, mint, parsnip, peas, spinach, squash, and tomatoes.
Pole beans and sweet peas, which rise high above the garden on stakes, help fix nitrogen in soil and enhance production while juicing up the soil for other high nitrogen feeders like lettuces.
Radishes are used as trap crops because they help repel cucumber beetles. This means cucumbers are also great companion plants.
Avoid planting near potatoes. Also, the perennial plant agastache is a bad companion for radishes.
GROWING STRUCTURE OPTIONS
A planting bed that sits on top of your existing soil. In general, raised beds should at least be 8 inches deep for your radishes to thrive.
Fast-growing radishes will thrive in pots – and this is also a great option if you have a garden area that struggles with root maggots.
In your containers, radishes will need at least 4 inches of soil depth, plus lots of water. Make sure your containers also have holes in the bottom for drainage.
A NOTE ABOUT CRUCIFEROUS CROPS
Before planting radish, which is a cruciferous vegetable, consider these important factors:
Make sure that no cruciferous crop or related weed (like wild radish and wild mustard) has been present in your growing space for at least 2 years (4 years is best).
This would include cabbage, cauliflower, broccoli, kale, kohlrabi, Brussels sprouts, Chinese cabbage, all mustards, turnips, rutabagas, and of course radishes.
Also, cruciferous plant waste should not have been dumped on these fields.
If your garden struggles with root maggots, growing your radish plants in containers is a great alternative.
Common challenges and their solutions
There are quite a few issues, pests, and diseases that can potentially harm your radishes. Not to worry. We’ve outlined them below, plus how you can avoid or fix the problem.
Your plants’ response to increased soil temperature or other stress, causing them to produce a flowering stem. The leaves may become hairy and bitter tasting, and whatever root has developed may become woody.
Solution: The trick to avoiding this issue is all about careful timing in the cool season, and regular monitoring of your crop.
Due to uneven moisture or dry soil, the roots of your radish may be forced to contract. If that is then followed by heavy watering, it can cause your radishes to split.
Solution: Keep your soil consistently moist to help minimize splitting.
MULTIPLE TAP ROOTS
This is an issue that’s caused by an excess amount of potassium in your soil. It can also happen when your plants are crowded, and have to compete for moisture and nutrients.
Solution: This is why it’s important to thin your radishes. That way, each plant has enough space to develop its roots and grow.
These pests suck your plant’s sap, causing it stress. Typically, mild infestations aren’t an issue – but in the case of a severe attack, they can kill your plants.
Solution: Try using sticky traps to get rid of aphids. A high pressure spray from your garden hose should also do the trick.
Also, you can try to attract beneficial insects like lady beetles, syrphid flies, and lacewings – all of which are important aphid predators.
SNAILS AND SLUGS
Snails and slugs feed on your plant’s leaves, eventually affecting its root production.
Solution: Hand-pick them at night, which is typically when they feed. You can also try putting saucers of beer on the soil around your radishes to attract and drown these pests.
CABBAGE ROOT MAGGOTS
They feed on the developing roots of your plant, leaving holes behind. Typically, the adult fly is attracted to the damp soil of your seeded bed.
Solution: Try using a lightweight floating row cover to prevent the adults from laying eggs on your newly seeded bed.
For the best level of protection, apply this fabric as soon as you sow your seeds, rather than once your seedlings emerge.
Also, make sure to remove any plant residue after harvesting.
You can also try spreading diatomaceous earth (a natural powder made from old aquatic creatures) around your plants while they’re seedlings, or you can use natural predators of root maggots, (nematodes or rove beetles) to kill them off.
Small black beetles that will jump when disturbed. They feed on seedlings, with the adults chewing tiny holes in the leaves. They can transfer diseases to your plants, and their feeding damage can kill young seedlings.
Solution: Use a lightweight floating row cover at the beginning of the season to prevent them from infesting your plants.
If you’ve got them already, then you can try using a homemade spray to control them.
Mix together 2 cups of rubbing alcohol, 5 cups of water, and 1 tablespoon of liquid soap.
You’ll want to test it first though – simply apply the mixture to a single leaf, let it sit overnight, then spray the rest of the plant if you don’t notice any bad side effects.
Also, you can use white sticky traps to capture flea beetles as they jump.
A fungal disease that mimics damage done by nematodes, and can survive for many years in your soil. It stunts your plants, leaving them with yellow leaves that wilt during the day. Roots will also become distorted and swollen with galls (growths).
Solution: You can add lime to your soil to reduce fungal spores, but typically this disease is difficult to control.
Your best bet is to keep your soil’s pH over 6.8 in order to better manage club root.
A disease that causes brownish-yellow lesions to grow on the roots as well as irregular blotches on the leaves. This bacterial disease is difficult to control since it stays in your soil for a long time.
Solution: Avoid planting in an infected area for about 4 years.
This fungal disease causes the yellowing of leaves with brown, curled leaf edges. The stem of your plant will turn dark brown/black, and it becomes slimy along with black, slimy roots.
Solution: Amend your garden bed with plenty of organic matter to improve its drainage, and practice crop rotation as well.
It’ll appear as white pustules (pimple-like growths) on the leaves and flowers, and the leaves might also curl and thicken. This particular fungal disease thrives in dry conditions and is spread by the wind.
Solution: Rotate your crops and plant disease-resistant varieties when possible.
If the disease progresses, then you can use a fungicide to manage its spread.
FUSARIUM ROT AND DOWNY MILDEW
Fusarium rot is a fungal disease that thrives in warm soil, while downy mildew is also a disease that’s caused by a fungus.
Solution: Keep your garden free of any plant debris, destroy your infected plants, and avoid overhead watering.
You’ll also want to improve the air circulation around your plants, and it helps to rotate your crops too.
This disease forms dark yellow and black spots with target-like rings on your plant’s leaves. The center of the ring often dries out and drops, giving leaves a shot-hole appearance. In advanced cases, the leaves might drop from your plant entirely.
Solution: Plant certified disease-resistant seeds when possible, and rotate your crops. Also, water your radishes in the morning to allow their leaves time to dry, then apply fungicide.
Be sure to remove and destroy any infected plants at the end of the growing season.
Harvesting and storing
Radishes can be harvested once their roots have reached full size, which is anywhere from 25- 45 days since seeding (depending on the variety you’ve planted).
To harvest, simply pull up your plants by their tops, then trim off the leaves. Next, you’ll want to wash them before sticking them in plastic bags and storing in your fridge for 2-4 weeks.
Keep in mind that radishes should be harvested before any heavy frosts or freezes.
If you’ve planted a daikon variety, their shoulders, (the top of the vegetable), will typically stand up out of the soil.
To harvest your daikons, use a spade or fork underneath your crop in order to harvest their long roots without breaking them.
When stored at 32°F (0°C) with high humidity, radishes will keep for four weeks or longer.