When I first began studying Tai-Chi with Master T.T. Liang in Boston, he told me, "Young man, you must get a root. A root, you must have it!" He went on to explain that a root is "when you can stand there and nobody can push you over." He explained that by doing the solo form and partner work, focusing on the twin principles of relax and sink, you would have a stance that would obey the commands of your mind.
Here are two direct quotes from my notebook from classes with Master Liang:
"After practicing for a long time you will have a root. You will be firmly rooted. This is called equilibrium. It means that no one can knock you over. When you are standing on two feet and someone pushes you 100 times, you can neutralize it with your waist. You will bend like you are boneless. All the weight will be sunk into one foot. this is called central equilibrium. When you acquire this, we can talk about self-defense."
"Having a root is when you can stand in one spot and nobody can push you over. You can stand and resist, or you can neutralize, without falling over. Both feet are glued to the floor.One foot is rooted 3 feet below the ground. To get a root, you must practice Tai-Chi twice per day, paying careful attention to the shifting of weight from one foot to the other. You must pay particular attention to maintaining the same height throughout the Form. When you do the postures, you must be relaxed and sunken deeply. The legs must be bent and the postures low."
So a root is a stance that is flexible, firm, changeable, with good balance, and endurance. You will then be said to have "attained central equilibrium and your waist and legs will obey your orders and wishes."
Here are six practices you can do no matter the form or style you practice. Try them for one week and you will easily start gaining, or improving, your root. Two are with a partner, so either wait until Covid19 is over, or mask up, wash hands, and no practice when sick.
1. Shifting and transferring weight from foot to foot in a slow, gradual, and detailed manner. Like pouring water from one glass to another, or like the sands in an hourglass, gradually change the weight from foot to foot. The slower and smoother, the better. This will develop Tai-Chi strength, train all parts of your legs, and give you greater awareness of how your stances and legs can be used.
2. Take empty steps, like when you are walking on ice, or walking at night. Balance and root on one leg completely, then lightly place your foot, empty of weight, and then gradually shift and finish. Imagine walking on ice, or if the kids left Legos out overnight and you are walking barefoot. Try not to fall heavily into your steps and stances. Empty steps helps train to not get your foot swept out from underneath you. After kicks, try to put your foot down with balance and control. Master Liang taught that "kicks are high steps and steps are low kicks." The mechanics for good stepping and kicking are essentially the same.
Empty stepping can make a rhythm for your solo form: balance-place-feel-transfer-finish. Remember, balance is a feeling, it belongs to the sense of touch. We don't use the eyes to see while doing our steps, the eyes are on the opponent, or looking inward. We take steps by feel. We feel where we step. If balance and stepping belonged to the sense of sight, then blind people could not walk, and sighted people could not walk in the dark, or at night.
3. Keep the same height when doing the solo form. There are some postures where you rise up like White Crane, High Pat on Horse, or the kicks, and some where you go lower, like Needle at Sea Bottom and Squatting Single Whip/Snake Coils Down. All others you can try to stay the same height which will work your legs and help you do correct whole body power mechanics. The Yang's family practiced under tables when they were young to develop their legs and waist.
4. Step out longer than usual and have lower and longer stances. You will have trouble doing empty steps, but this will really work your legs. My experience is that the lower I go, I don't worry about empty steps, and I use a faster pace. If I'm higher, doing empty steps, I'll drastically slow down my pace, which also works my legs.
5. Except for a few places, make sure your weight is never evenly distributed between your feet. Always have one foot be responsible for support and gravity. Take a Bow Stance for example, depending on your school, style, or teacher, you could have 70, 80 or 100 percent of your weight on the front foot upon completion. When the weight is 50/50, it tends to just make the legs tight and hard, unable really do anything but be there. Equal weight is hard to step, difficult to turn, and too stuck to push. That's why the Classics warn against "double-weighting" or weight equally on both feet. There are some Horse Stances in the weapons, Ta-Lu, and San-Shou, but the vast majority of the time we need to distinguish "full and empty" between our feet.
6. Testing stances by having a partner push against, lean on, and pull our stances. Use structure and bones for resistance. They can lean ,we don't. We channel their weight and energy through our structure, i.e. our stances, into the ground.
7. Rooting Drill from Pushing-Hands. There are many drills to get the skill of Rooting in the Pushing-Hands practices. Pushing a partners chest, hips, Ward-Off, pulling their Ward-Off, pushing their stance from four directions, all these drills help develop a root. I will be posting a video with these and other Rooting Drills.
Take your time, work on one or two of these methods, and gradually and steadily you will progress to "getting a root."