Figuring out when your peanuts are ready is a lot like deciding when to harvest sweet potatoes.  First, check the days to harvest.  We grow one of the few varieties with a short enough season to mature in zone 6 (Early Spanish --- 100 days to harvest), which means that we could potentially dig our peanuts anytime after the first of September.

Various websites admonish you to wait until the leaves on your peanuts are starting to yellow, but it's now nearly a month after our peanuts are supposed to be ripe, and we haven't seen any yellowing.  However, the plants did mostly stop blooming a couple of weeks ago, which I suspect is a good sign that they're nearing maturity.

If you think the date is close enough, dig up a test plant.  To dig peanuts, sink your shovel straight down into the soil about six inches away from the plant's stalk and lever the pointed end toward the plant, loosening the soil underneath.  Then gently lift the plant out of the soil.  If the ground is clayey and too wet or too dry, you'll lose peanuts in the process, so it's best to make sure your soil is moderately damp before digging a test plant.

Shake off any clods of dirt, then take a look at the beautiful peanuts clustered around the plant's roots.  There will definitely be a few paler peanuts that aren't yet fully formed, but if the majority are full-sized (like in the photo above), you're probably in good shape.  To make sure, crack a shell open --- are the nuts filling up the whole shell inside?  If so, your peanuts are ready to dig.  (Take a minute while you're peering at the roots to notice the nitrogen-fixing nodules lower down --- pretty cool, eh?)

Dig your whole patch just like you dug the test plant, then put them on a screen or in another airy location to dry.  Don't eat any of your bounty yet (including that test peanut!)  Fresh peanuts contain a mild toxin and need to cure for a few days before they can be eaten.  Once you've waited the requisite time, check out my post about making your own peanut butter!