What you need to know about growing root vegetables

Growing root vegetables is a waiting game. For the most part, you have no idea how successful your crop will be until it's time to harvest. And it's pretty discouraging when you go to dig up your root crops at the end of the growing season, and all you turn up is soil and a few small, misshapen roots.

Fortunately, once you know the basic characteristics and requirements that root vegetables share, you'll have much more confidence and luck growing root vegetables in the future. Keep reading for some need-to-know information so that, no matter which plant you choose, be it carrots, sweet potatoes, parsnips or something else altogether, you'll have a much better chance for success!

Let's start with a little clarification on what a root crop actually is. Encyclopedia Britannica defines root crops as those with an underground edible portion that is truly made up of root cells. Potatoes (tuber), ginger (rhizome) and onions (true bulb) are, for simplicity's sake, actually modified stems of sorts, and not true roots at all. You can dig into the details more on your own if your curiosity has been stirred. There's a lot to it. For the sake of this article, however, the following tips are helpful for growing most any plant whose underground portion is used as a vegetable.

Here are some helpful tips to consider before growing any plant that you have to dig up/uproot from the ground to eat.

1. Prepare the soil. First and foremost, root vegetables are prized for the part that forms underground — in the soil. As such, soil is top priority. If you plant root vegetables in compacted, clay soil, you are setting yourself up for disappointment. If you do nothing else before planting your root crops, amend the soil with organic matter, ideally compost. Even better, raise the soil off the ground 8 inches (20 cm) or more to ensure a good foundation. Aim for soil that is loose and loamy and rich in color. Consider a soil test this fall, so you know the pH and nutrient status of your garden's soil and can amend accordingly. The University of Minnesota Extension cautions that root vegetables do not do well in soil that's too acidic. The ideal pH is somewhere between 6 and 6.5. Be careful not to overfertilize, especially with materials high in nitrogen. This can lead to beautiful-looking plants above the soil but nothing to harvest beneath the soil.

2. Avoid transplanting root crops if possible. Root crops are not ideal for starting indoors. Since the root is the part you want to eat, disturbing the root system could stunt or distort the root's growth. This is especially true for root crops with a single primary root, like parsnips and carrots, which, according to the University of Minnesota Extension, will likely fork if transplanted. In general, plants will produce much stronger, more uniform roots if they stay right where they are sown throughout the growing season.

3. Water even more thoroughly. Don't increase how often you water. Rather, water your root vegetables deeply. The general rule of thumb is that plants need about an inch (2.5 cm) of water per week, whether through rainfall or supplemental watering. But with vegetables, we simply recommend that you water when needed (when the top couple of inches [5 cm] of soil are dry, but you can still feel moisture below that).Keep in mind that roots follow water. Therefore, lightly watering your plants will result in shallow root systems. This is not at all what you want when you're trying to encourage well-formed root crops. Watering deeply and thoroughly, on the other hand, encourages deeper, well-formed roots.

4. Make sure your root vegetables get enough sun. Sun is what plants use to make energy, and for root vegetables, you want to make sure the plant has enough energy to produce a substantial root. Make sure your plants are exposed to the sun for ideally six hours or more each day.

5. Allow adequate space for roots to grow. Keep root crops thinned appropriately and prevent weeds from crowding them. Thin your seedlings by anticipating how large the mature root will be. This mostly applies to plants with a primary root. Tuberous roots, like of vining sweet potatoes, will need even more room to grow.

A couple more tricks of the trade:
Since root vegetables don't rely on pollinators, try growing them under row covers. This will protect your crop from many flying insects as well as four-legged critters. Be sure, however, that your plants still receive enough rainfall/water.

Also, consider intercropping fast-growing root vegetables with slower-growing ones. For example, the University of Minnesota Extension suggests sowing radishes and parsnips together, since radishes will be ready to harvest before parsnips really start taking off.