Growing in a 12 Gallon Container
Fresh horseradish root is a seasonal item in Hawaii. A few of the markets on Maui have it for sale during December as it's traditionally eaten with prime rib or other expensive cuts of beef.
Horseradish is normally planted in the spring and harvested in the fall, after the first frost, or in the following spring before the leaves begin to grow again. In Hawaii, it can be planted at any time of the year. It's an invasive plant and not recommended for a raised bed or a square foot garden.
In June of 2009, I planted 2 medium size root pieces in an 12 gallon container. I planted the roots in a good quality potting soil amended with well rotted compost and an organic all purpose fertilizer. It didn't take long for the roots to begin producing leaves. The plants need a lot of water and monthly applications of an organic or natural all purpose fertilizer.
Through the year I cut back the older leaves. When the plants were well watered and fertilized the leaf growth was prolific.
The only pest problem I encountered was the cabbageworm, the larvae of a white moth. They're active from late November until March. Since I wasn't using the leaves I didn't cover them with tulle like I did the cabbages and other leafy green plants. Periodically, I searched for the cabbageworms and removed them from the container. Occasionally, I found slugs in the leaves but they didn't seem to do any noticeable damage.
The 1st week of August, at 14 months, I harvest the plants. That wasn't an easy task and it seems like harvesting the roots would be even more difficult if the horseradish had been planted in the ground.
First I cut off all of the leaves and then loosened up the soil around the edges of the container. This area was filled with small, fibrous roots. Then I pulled the plants, surrounded with potting soil, out of the container. Unlike radishes, the roots are a tangled mass. The best solution to getting at the individual roots without breaking them in pieces was to hose the soil away from the roots. It took quite a bit of water to accomplish this.
After I reduced the soil to what's shown in the photo above, I put all of this into a large bucket of water to loosen the remaining soil that's still inside of the root mass. The root mass, not including the crowns that were above the soil, was about 16 x 16 inches.
I had no idea if horseradish would grow in Kihei as the fall and winter temps are so warm. The plants didn't produce the large roots that are sold at the market but there were lots of roots large enough to grate.
When I searched online for other gardeners experiences, it seems the results I had were normal, even for roots or crowns that were planted in the ground. Although most recommended harvesting in the fall for the hottest results, the roots I harvested were definately hot.
July 26, 2011
In early July of 2011, I planted 1 of the crowns from my August 2010 harvest in a 15 gallon Smart Pot. The crown has been in the refrigerator all this time. It started growing as soon as I planted it and has grown exponentially in 4 weeks. I decided to try growing horseradish in a Smart Pot since it worked so well with culinary ginger. It was easy to dig down and harvest ginger roots when I needed them so I'm hoping it will be easy to do this with horseradish.
November 17, 2013
After almost 2.5 years I harvested the container and this time there were were several large roots. I did periodically pull up an easy to access side shoot to use as fresh grated horseradish. It's much easier to do this from a Smart Pot than a hard plastic container.
When horseradish is planted in a Smart Pot it's best to put the pot on a solid surface like concrete. Smart Pots are made of fabric and the fine hairs or capillaries from the horseradish roots will grow right through the fabric and begin rooting in the ground, I found a large concrete stepping stone that was a little larger than the base of the pot and it blocked the roots from growing outside of the pot.
Horseradish roots or crowns for planting are not the easiest item to find. There are limited suppliers that will mail them to Hawaii. They seem to be most available in March and April and they sell out quickly. I purchased roots on ebay and from Heirloom Acres Seeds. They can also be obtained online from Territorial Seeds.
Following is a link to a blog post for preparing fresh horseradish:
As the article points out, it's very important to process the horseradish in a well ventilated area or outdoors. The ventilation is particularly important after the vinegar is added. At that point, make sure to keep an arms length distance from the processor when opening the lid to push the horseradish down from the sides of the work bowl as the initial concentration of fumes can be asphyxiating.
Recipes and unique ideas for using horseradish: