"I have a hypothesis that the last chance of frost is past when the pecan trees are in full leaf," my father posited.  "What do you think?"

The idea appealed to me, in part because of the old saying that it's safe to plant your corn when the oak leaves are the size of a squirrel's ear.  I saw oak leaves twice this big a week ago along with volunteer squash, tomatoes, and sunflowers.  Ever since, I've been pondering whether I'm really going to put out half of my summer garden three weeks before the frost-free date.

Meanwhile, the scientific side of my mind sidetracked into finding out what cues trees use to decide when to leaf out.  The only options I could come up with are soil temperature, air temperature, and day length, all three of which (along with the ten day weather forecast) are what I use to determine my own planting schedule.  A search of the internet, though, suggests that our trees are keeping track of how much cold weather they've faced, and when they think they've had enough, they leaf out (as long as the air is warm enough.)  That would mean that an abornmally cold winter (like this past one) would produce an early spring (like this one) since the trees would have counted up the required number of chilly days earlier than usual.

Put that way, I'm not so sure I want to base my planting date on our trees' decisions.  However, the soil has warmed to 60 degrees and the ten day weather forecast predicts no lows beneath the mid forties, so I went ahead and planted green beans, corn, squash, melons and cucumbers (in quick hoops), okra, mung beans, and basil, along with sunflowers, millet, ground cherries, and amaranth in the forest pasture.  I'm going to hold off on putting out my homegrown pepper sets, though, until the night lows are just a bit higher.

How about you?  Are there trees that you feel confident predict the time to plant your summer garden?