It's not an easy question to answer. January's best plants will depend on what your climate is like and the soil you are in. Here are some suggestions. Apart from vegetables, you can also plant fruit and flowering plants. You can also plant annual flowers like roses and tulips seeds or seedlings. For help in deciding where to start, check out my article on January planting tips.
Zones 7-8 can be used to grow onions indoors. There are many ways you can grow onions from seed. It is recommended that you plant them approximately eight to 10 week before you plan to plant them. For sweet onions to mature, they will need at least eight weeks to be ready for planting outside. In Zones 5-7 onions should be planted eight to ten week before you intend to plant them.
To force rhubarb to bloom, wrap the crown of the plant in straw and place it in a large container or terracotta. Blocking the light will make the stems grow. Root vegetables can be forced if they're directly seeded. They aren't very transplantable but they're still good ideas. They are hardy and can withstand the winter cold. They'll bloom when they get to a warmer place.
Planting strawberries is an easy and quick way to add fresh produce this winter. Woodland Strawberry can be grown in January. If you plan to plant it in the spring however, you'll need wait until the weather is warmer. Be sure to thoroughly soak the roots before planting. You can plant bareroot fruit trees in January if you have a sunny window.
Even though vegetables can be planted in all climates, it is important to keep in mind that certain plants will need to grow in colder regions. For example, herbs such as basil, oregano and parsley that are longer-growing need to take eight to 10 weeks to mature before they flower. These herbs can be planted indoors or brought outside when it is cold. And in winter, make sure you keep them moist and clean.
Cool-season vegetables, like spinach and lettuce, are great for vegetable lovers. You can cover your plants with a frost cloth to protect them from the cold, or use a small hoop house for them. You might also want to try planting cool-weather plants if possible. While they may need to be started sooner than you think but they will still be ready in a few months.