Turnips are an easy annual to grow. in Texas they like to be grown any time except summer. Delicious and nutritious. They are nothing like storebought. Jerusalem artichokes are great, but tend to be invasive, good starch for diabetics. Can make a wall of plants quick providing shade for other plants that don't like so much heat. They are a sunflower, but the seeds are for the birds. The stalks provide good sticks. If you leave some roots in the ground they spread easily. A large amount of return for very little work. All farm animals seem to like to get into them and dig them up though. Daylilies are an excellent perennial root vegetable . They will naturalize when planted, and they get bigger and bigger each year. One plant will put out many blooms which make a delicious vegetable for one day (hence daylilies), but the dried blooms are good in soups. The unopened buds are similar to green beans in appearance, and are also delicious, all parts of this plant are good raw or cooked, and it is a native. I also eat the roots of lesser ragweed while I'm cleaning up the garden. They run along just under the surface spreading the plant early in the spring. It is thought that some degree of allergy resistance is formed from eating the plant.I have no problems from it. But I don't know about other people. It tastes like water chestnuts, but is a skinny little tuber. Cattails are a wonderful tuber to eat, and they take care of themselves pretty much, and of course every part of this plant is useful, if you have a pond or marsh or ditch that fills with water to grow them in, but they store some toxins, so the water and soil that they grow in must be good already, if not, cattails will improve the quality of water and soil. If you live where there is enough water and not too much cold and probably acidic soil, kudzu makes a good root vegetable, but is considered invasive. This is a nutritious plant used throughout the world with a fascinating history in the US. It is illegal to sell the plant here, but you can go gather it where it does grow, and confine it in your garden. It is a legume and builds the soil, It's leaves are nutritious for livestock, but it is so very invasive.It is the fastest growing plant in the world.It does not produce seed in the US. It has no enemies or pollinators here. It has many many uses.I like parsnips, and you have to love dandelions. Dandelions may be the winner for most nutritious root, and you just have to get it going and leave it alone. It is not native, but it likes it everywhere. Comfrey is a good nutritious herbal root to have on hand and is easy to grow if you can keep all the animals away from it.