Fertilizer for Radishes

Radishes grow well in generally fertile soil, but there’s such a thing as too much fertilizer for radishes. A little bit goes far.
By: Nan Chase

Botanical Name: Raphanus sativus

Radishes need little in the way of fertilizer added to soil. In fact, a common problem with growing radishes is having too much of certain elements, usually nitrogen. The results may include spindly radish roots, overly thick greens on top, inferior flavor, and low levels of antioxidants in the mature radishes.

Well-balanced soil in the vegetable garden will contain a mix of several important nutrients: nitrogen, phosphorus, and potassium. Let’s look at how they work together.

Nitrogen nurtures plant leaf development, so leafy crops like kale and spinach need a lot of it. Phosphorus helps several aspects of plant development, including flowering, root growth, and the transfer of water content and energy through the plant structure. Potassium nurtures root growth, which is crucial for healthy plant growth.

When there’s too much nitrogen – it’s easy to over-fertilize – a root crop like radishes will suffer because the plant is trying to make the leaves as big and profuse as possible. What happens to the roots? They simply can’t form correctly or grow big and plump.

The root – the part of the radish we eat most commonly – is starved for nutrition and may appear long and skinny rather than round and full. In addition, the special flavor of a radish may not develop properly, either, and even the normally high level of antioxidants in the radish may be suppressed.

Radish fertilizer requirements, then, are minimal. If you apply commercial fertilizer to the garden be sure to look for one with a low nitrogen content. Standard garden fertilizers are marketed witha series of three numbers, for example 5-20-10; the numbers indicate the percentages of nitrogen, phosphorus, and potassium – in that order. If that first number is low, that’s good because it indicates a low nitrogen fertilizer. If the number were 20-10-5 it would indicate a much higher percentage of nitrogen than is recommended.

Now, gardeners who make their own soil amendments from ingredients at hand can add certain components with lower nitrogen content. Examples are sawdust and straw, both of which require the slow decomposition that keeps active nitrogen levels fairly low.

Nurture your radishes by providing a low-nitrogen soil that still contains plenty of organic materials mixed in. Leaf mold is a good mixer. It’s important to give radishes a fairly loose, open soil so that the roots can develop easily.

A heavy clay soil is difficult for growing radishes, so it may be necessary to help clay soil develop a better texture. One way to do that is to work some powdered gypsum into the soil. That helps the clay particles clump together and leave more room between the particles; water and nutrients can move better.

Finally, soil that’s too low in pot ash may not enable radishes for form round bulbs. In that case try adding commercial potash or some hardwood ashes.

The best radish fertilizer may be no fertilizer at all!

Next Up

Harvesting Radishes

Timing and technique: get them right for a delicious harvest of radishes that lasts for week or months. Ready, set, pull!

Radish Plants

This tangy root plant comes in all shapes, sizes, and colors, and makes a good beginner’s fresh vegetable because it germinates and grows so fast.

Growing Organic Radishes

Radishes grown organically serve up helpings of high-fiber, high-flavor food. With care the harvest lasts much of the year.

Growing Winter Radishes

Some radishes love, love, love the cool weather during fall and winter. Try their versatility in stir fry cooking and pickling.

Growing White Radishes

White radishes come in two distinct types: early, quick-grow white, and long-season slow-growing white. Both are great.

Growing Rapid Radishes

Radishes are quick to germinate and grow to maturity, hence the nickname “rapid radishes.”

Growing Radish Greens

Radish greens are easy to grow and perform well in the kitchen too. Say hello to an economical, nutritional cool-weather crop.

Radish Companion Planting

Companion planting with radishes makes sense, as there are many friendly neighbors that can benefit from radishes nearby.

Growing Radishes Hydroponically

Growing radishes hydroponically requires some investment in equipment and supplies – and attention to maintenance – but it works.

Growing Summer Radishes

Most radishes aren’t known to thrive in summer conditions, but careful selection and growing practices can produce good results.


7am | 6c
7:30am | 6:30c

This Old House

8:30am | 7:30c

This Old House

9:30am | 8:30c

Insane Pools

12pm | 11c

Insane Pools

1pm | 12c

Fixer Upper

4pm | 3c

Fixer Upper

5pm | 4c

Fixer Upper

6pm | 5c

Fixer Upper

7pm | 6c
On Tonight
On Tonight

Fixer Upper

8pm | 7c

Fixer Upper

9pm | 8c

Fixer Upper

10pm | 9c

Fixer Upper

11pm | 10c

Fixer Upper

12am | 11c

Fixer Upper

1am | 12c

Fixer Upper

2am | 1c

Fixer Upper

3am | 2c

Salvage Dawgs

4:30am | 3:30c

Get Social With Us

We love to DIY. You love to DIY. Let's get together.

Consult Our A-Z Guide

Everything You Need to Know

Browse a full list of topics found on the site, from accessories to mudrooms to wreaths.  

How-To Advice and Videos

Get video instructions about kitchens, bathrooms, remodeling, flooring, painting and more.

Watch DIY Downloads Now

Watch DIY Network LIVE

Don't miss your favorite shows in real time online.