We woke up on Monday morning to a welcome chill that seemed to last most of the day.  It felt an awful lot like the first hint of fall.  This “Fall Fakeout” is fairly common for our area, and it is almost always ends with at least one more round of very hot weather sometime in September.
Having a period of cooler weather for at least a couple of weeks in the late summer is absolutely crucial to our farm though.  Almost all the crops we will be harvesting from October through January are planted during August and September, and most of them are sensitive to high temperatures.
About half of our fall crops are direct seeded.  Temperatures over 100 degrees will kill the tiny seedlings if they have the bad luck to be emerging from the ground at the wrong time.  Sprinkling the field can help keep the soil cool for a day or so, but if it stays hot for several days it’s pointless to try to save them.  Normally it’s better to just replant once the heat has passed, and every year we lose at least one field this way.
Weather forecasts are essentially useless when deciding when to direct seed.  Carrots, for example, take almost ten days to start emerging from the soil — far beyond the accuracy range of most weather forecasts.  Sometimes it’s best to plant during a hot spell rather than a cool one, and hope it cools off by the time the seeds are coming up. As often as not, we just plant on a schedule and hope for the best.
The other half of our fall crops are transplanted, particularly broccoli and cabbage.  These crops present a very different problem than the direct seeded ones.  The small plants are vulnerable to the heat immediately upon planting, but then “harden off” after a few days in the ground.  It’s never a good idea to try to set them out on a day when it’s going to be extremely hot.  Of course we only transplant during the early morning hours, from 6 until around 10.  But during the worst heat waves, it can be too hot by 8 am.
Transplants set out during a long heatwave may survive, but they are often stunted and weak, making them easy prey for insects and diseases.  In an ideal scenario, it’s best to simply wait for the heat to break or at least back off a little, then try to get as much planted as possible before it gets hot again.  Unfortunately, the plants growing in the nursery don’t always cooperate:  sometimes they aren’t ready to put out when you want them to be.  There is also always the risk that they will get too big and rootbound if you keep them waiting too long.
This is the first cool weather we’ve had on the farm since mid-June, and we are planning on taking full advantage of it.  Indian Summer is coming, and we want to be ready.