Growing Horseradish is Easy!

Jenna Zanchettin
Apr 4
4 min read

Updated: May 17

Horseradish is a hardy, perennial herb known for its spicy roots, often used to add a fiery flavour to various dishes. In New Zealand, growing horseradish is simple, and with the right care, it can be a lasting addition to your garden.

This herb serves as an introduction to root propagation, allowing you to create new plants from cuttings. Horseradish is particularly interesting due to its sharp and spicy nature. Unlike the common practice of taking cuttings from leaves, as you would have done in your houseplant era, this involves root cuttings. Root cuttings are a propagation method used for a limited variety of plants that cannot be propagated through other means. Although it may sound scary, it's actually quite simple because root cuttings can be obtained either by digging up the plant to get your cuttings or by carefully digging around the base of the plant while it remains in the ground, and a warm temperature isn't needed for the success of creating these new plants.

What makes a good cutting?

The choice of plant part for cuttings impacts their success. Root cuttings from younger plants or the younger section of the plant typically thrive better than those from older plants because young, fleshy roots tend to grow more easily than older, woody ones.
To propagate plants successfully from cuttings, it's important to identify the best type of cutting for the specific plant - a quick internet search can help. For instance, new horseradish plants are propagated from root material, not leaf cuttings.

Recognising the best time of year to take cuttings is essential. The perfect period for root cuttings is when the plant is dormant with minimal foliage, typically in winter for most plants needing root cuttings. However, in warmer climates, the horseradish plant might still have some foliage.
One of the most crucial aspects is to ensure that the plant from which you are taking cuttings (the parent plant) is healthy and well-hydrated. It should be free from pests and diseases, as these can result in weak new plants when poor plants are used.
Additionally, caution is exercised when extracting materials from the parent plant to avoid damaging any roots in the process..

Method

Once you've unearthed some plants and cleaned off the soil, it's important to disinfect the roots. Soak them in a solution of 3% hydrogen peroxide for 30 minutes, using 2 tablespoons (30ml) of Hydrogen Peroxide 3% per 1 litre of water. Alternatively, soak the roots in a household bleach solution, mixing one part bleach with 20 parts water, for 10 minutes. Rinse thoroughly with fresh water afterwards. Avoid using rooting hormone at this stage, as it is unnecessary.

While the roots are soaking, prepare your pots. Fill them with Seed-Raising mix; 10cm pots are ideal as they can accommodate about 3-5 cuttings, depending on the width of your cuttings.

After 30 minutes, prepare your cuttings by slicing them into 4–5 cm lengths.
Using sharp, sterile Secateurs, make a flat cut at the top of the cutting (the proximal end) and a slanting cut at the bottom (the distal end). This helps identify the ends, preventing the cuttings from being planted upside down. Trim off any thin side roots, as they do not contribute to growth.

Plant the roots vertically, with the top end of the cutting just below the surface, and water them.
Plant the cuttings in containers placed under cover, such as beneath the eaves of your house, in full sun. While they are rooting, it's crucial to keep the rooting medium moist. Once the foliage appears, monitor it to prevent the leaves from getting burned and turning crispy. This observation applies to all new growth on all plants. Use Shade Cloth if necessary or move the plants out of direct sunlight.

After the new plants have established robust root systems, it's time to move them into larger containers filled with well-draining Potting Mix Soil. Choose a spot that receives plenty of sunlight. Given that horseradish tends to spread quickly, it is advisable to plant it in a specific area or within a sizable container to manage its growth effectively.

Harvesting: Typically, the roots can be harvested 16 to 24 weeks post-planting. Leaving them in the pot until after the frost can enhance their flavour.

By following these steps, you can successfully grow and propagate horseradish in your New Zealand garden, enjoying its spicy roots for culinary purposes and even using its leaves for natural remedies.

Glossary:

Propagation:

Propagation is when you make new plants from an existing one. It's like taking a cutting or a part of a plant, like a leaf or stem, and growing a whole new plant from it! And in more detail and so you can level up. Plant propagation is the process of creating new plants from a variety of sources, such as seeds, cuttings, or parts of existing plants. This can occur through methods like sexual propagation (using seeds) or asexual propagation (using cuttings, grafting, roots, or tissue culture) to produce genetically identical plants.

Perennial Herb:

A perennial herb is a type of plant that lives for more than two years and continues to grow back every season. Unlike annual herbs like basil (in NZ), which only live for one year, perennial herbs come back year after year, often growing new leaves or stems during the growing season.

Examples of perennial herbs include mint, rosemary, and thyme. These plants don’t need to be replanted each year because they survive through the winter and regrow when the weather gets warmer.

Dormancy:

Dormancy is a phase in a plant's life cycle where growth pauses to conserve energy and survive harsh conditions like extreme temperatures or drought. Metabolic processes slow, and the plant may shed leaves or become inactive until conditions improve.

Rooting Hormone: Rooting hormone encourages root development in plant cuttings, often containing auxins that stimulate growth. Applying it to cuttings enhances propagation success. Available in powders, gels, and liquids, it significantly improves the chances of growing new plants from cuttings.

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Although this gardening blog shares my experiences and factual horticultural information, remember that your gardening journey is unique to you. Adapt, experiment, and learn from your own experiences; that's all part of the process.