Eat the Weeds Newsletter 22 September 2015

Eat the Weeds Newsletter 22 September 2015

by Green Deane

People often say they can’t find Purslane. I have a hard time avoiding it. This clump, along with two non-edible versions, was seen next to a park bench by LakeMinneola in Clermont. Photo by Green Deane

Frost. Do some vegetables and fruit taste better after a frost. Yes, but first let’s talk about frost.There are at least five kinds of frost but for our purposes we are interested in two, advective and radiation.

Frosted Grass in Florida

Advective frost is the minor exception so we’ll visit it first. It happens on windy nights when frost usually doesn’t occur. The conditions have to be just right: A cold front comes through, it’s windy and cloudy and there’s a thick layer of cold air, a mile high or more. Under those conditions there can be a frost. Usually a nightly breeze without a front going through means no frost. The more common kind of frost is radiation.

Beyond CitrusTower in Clermont, FL, one can see the low-lying frost/freeze damage.

That frost happens when the sky is clear and the wind calm. With clear skies heat from the earth rises creating an inversion: The warm air goes up and the cold air comes down, perfect conditions for a frost, cold and no breeze. Also know that cold air runs down hill so frost is more likely at the bottom of a hill than in the middle. If the hill is high enough to reach colder air it can have frost at the top as well. Here in Florida one used to be able to see that in freeze-bitten citrus groves. They’d have dead trees on the tops of hill and in the valleys but still live ones on the slopes. Now they are housing developments. Incidentally, wet soil can make the air temperature right above the soil five degrees warmer than dry soil and can hold the temperature until sunrise. You can find your average first and last frost date for your area. Locally late December is the first, mid-February is the last.

A common window decoration when I was young, on either side of the pane.

Local conditions can moderate frost and freezing temperatures. I planted a Star Fruit tree outside of its range but it grew to produce because it was next to a cement block house and a 25,000 gallon pool. That produced a micro-climate that kept it happy and well, in the back yard. Several attempts to plant mango trees in the front yard, however, failed. Not 30 feet away the front yard is always colder and has frost more often. I’ve noticed that well-established mango trees, planted decades ago when it was warmer in the winter, are alive but they don’t produce much now. Also note it can be warmer in cities because the buildings absorb heat. Many weeds that might get frost-bitten in the countryside can over night well in the city.

Our winter radish likes the cold weather. Photo by Green Deane

As for vegetables some members of the Brassica family, a group that can take cold temperatures, are noticeably less bitter after a frost. This includes Brussel Sprouts, Broccoli, Collard Greens and Kale. Leeks taste better after a cold snap as do Carrots and Celeriac. Swiss Chard, which can be bland, can be more flavorful after a frost. But these are cultivated vegetables. I can’t argue that a wild food like, say Bull Thistle, tastes better after a frost but it is in the fall, just before winter sets in, that the root is at its fattest. The same can be said of many mustard family members as well. I think our winter mustards are milder than their spring versions. With all of that said, what of frost and fruit? The obvious candidate is the Persimmon but apples and grapes can squeak in as well.

Chilling or freezing does not improve persimmons’ flavor.

You will hear that persimmons are best after a frost but that is more of a coincidence than a meteorological fact. The species of persimmon here in Florida is the same found in northern states. Its fruit ripens soon. Mid-October is considered the average peak of season here which is about two months before any frost or cold weather. The week before or the week of Christmas is our first frost/true cold weather dip. As we don’t have a frost and the persimmons ripen anyway a frost is not necessary to sweeten persimmons. Indeed, the best persimmons are the ones you have to fight the ants for (on the ground.) I think persimmons and frost got connected in popular culture because the fruit can persist on the tree long after the leaves have fallen away. Indeed, the Persimmon tree is among the first to lose its leaves is the fall (and among the last to leaf out in the spring.)

October apples in Maine. Photo by Green Deane

As for apples and grapes... I walked to school, four miles each way, and that took me past an 80-acre blueberry field, through an apple orchard and by a hedge row of concord grapes. While blueberries were well-picked over by fall I think the persistence on the tree or vine of apples and grapes and subsequent minor dehydration accounted for their sweeter taste. Even some crab apples can get a tad better the longer they hang on the tree.I also hunted half a century ago and learned early on one found game near these species. Deer and partridge were common finds near apple trees in the fall.

So frost certainly does help at least one family of plants — the Mustard family — but doesn’t do much for most fruit, though I am sure in the comment section we will hear some different views.