After the harvest, you will need to clean what you picked.
Greens especially need cleaning. They tend to be low to the ground, and when it rains (or you water your garden), bits of soil and mulch splash up and cling to the leaves.
Nobody wants to eat gritty, dirty greens.
Greens can be a bit tricky to clean up, but with practice you'll become more efficient. You'll enjoy your homegrown greens without any annoying dirt or grit.
If you don't already have one, get a salad spinner.
On second thought, get two! It's handy to have a couple of them on hand, and even better if you have a smaller one and a larger one.
Greens are delicate and would wilt quickly if placed in warm or hot water. You must use cold water. It doesn't need to be ice cold though! Cold tap water is sufficient.
Use enough water such that the greens float. I prefer to use my sink, but you can use a large bowl or similar.
While the sink fills with water, pick through your harvest. Separate leaves if any are bunched together and remove any roots, if you pulled the entire plant out to harvest.
Throw away any brown, rotted, or partially eaten leaves. But...
Once the greens are in the sink, swish them around gently to loosen any bits of grit or soil stuck to the leaves.
Then let the leaves sit in the water for a few minutes (5-10) or longer. Don't swish them at this point. You are waiting for the water to settle and for the unsavory bits to sink to the bottom.
You may find small insects or other critters that came inside with your harvest clinging to a leaf floating on top! I've found katydids, slugs, spiders, ladybugs, and caterpillars.
Carefully remove the sink stopper and allow the water to drain. I like to collect the greens with my hands, fingers spread out, and gently hold them up against the side of the sink while the water drains.
Don't agitate the water too much to disturb the debris that has sunk down to the bottom.
I wash my greens at least twice in the sink. Greens are full of nooks and crannies and dirt tends to get worked up into the leaves where it can get stuck. It can take a few rinses to get it all out. Repeat until the rinse water is clean.
Place the drained leaves in the salad spinner and evenly distribute them around the basket. Then, spin!
A vigorous spin will force the excess water off the leaves, effectively drying them. In reality, the leaves will still be a bit damp, but they should not be dripping.
You can take them out of the spinner and air dry the leaves a little, if you like. I usually like to keep my greens ever so slightly moist, as I find they keep crisp with a little moisture. Strive for a similar amount of moisture as you find in bagged salad mix. Don't leave the greens sitting out too long because they will start to wilt and dry out.
I put my greens in a plastic produce bag (like you get in the grocery store), close with a twisty tie, and place in the crisper drawer of the refrigerator.
If you want to freeze your greens (for example spinach, Swiss chard, collards) you can do so at this time. Find instructions for freezing greens online or in a reference book, because greens sometimes need to be blanched in boiling water briefly before freezing.
Head lettuce is difficult to clean while keeping the head intact. You don't have to wash it at this time, and plan to wash the lettuce after you've cut or torn it up for a salad (etc.).
If you want to wash it now, plunge the head in the water and allow it to drain as best you can.
But, the water gets up inside the head and can get stuck there! To drain the head, I hold it upside down and shake it gently. Then I rest the head on a towel and reposition it every few minutes to allow the water to find its way out.
Fortunately, the inner parts of the head tend not to collect much dirt and debris. Those leaves are protected by the outer leaves as the head grows.
When you are ready to use the lettuce, you can rinse and spin-dry the torn leaves one more time.
Having a large salad spinner is helpful for larger greens like Swiss Chard. You can eat both the stems and the leaves and it can be tricky to fit the long stem and leaf in the basket of the salad spinner. I bend them gently to fit in the basket. Make sure the leaves aren't all clustered together, but rather they are distributed around the basket. The water will be expelled more effectively.