The Greenhouse Boost

May 6.  Transplant  Day

First, let me go back almost two months, to May 6. This was when the tomato plants arrived, and I rushed to get 25-30 seedlings transplanted and into the greenhouses.  Conventional wisdom has always been, however, that Seattle's frost-free date was May 15. Not anymore. The average frost-free date here is actually the end of March but yes, there can be cold snaps well into May. But after 30 years of living here (Hardiness Zone 8B - see charts) I am convinced that, with climate change,  the real frost-free date is probably closer to May 1: "official" publications are just reluctant to make the change.

I also had the confidence that I was putting the plants into my two plastic greenhouses, which elevate the daytime temperatures, and tend to lessen the nighttime drop. (We are also very close to Puget Sound which moderates temperatures as well at both ends of the scale.)  However, this year, the fates brought us an unusually warm May. Almost the entire first week of May 6 was sunny and warm, with highs in the 80's. My problem, it turned out, was not keeping the plants warm, but overheating them!

When the sun is shining directly on them, the greenhouses often rise 10-20 degrees higher than the ambient temperature. And since tomatoes do not really like heat over 90 degrees (they will drop flowers and fruit) or high humidity I tend to leave the windows and doors open whenever the temps reach 80 or more, both to keep things from getting too hot, but also to increase healthy airflow.

Starting in a greenhouse has its advantages and disadvantages.

PROS :

*   Higher daytime temperatures speed growth - tomatoes thrive in 75-85 degrees
*   Cuts down on cooling wind
*   Moderates night-time temperatures

CONS:

*   Danger of overheating
*   Excess Humidity
*   When flowers bloom, should be hand-pollinated (no wind, no pollinators)

Complicating this scenario (which would tend to favor greenhouse starts, I think) is the fact that because I ran out of greenhouse space this year, I was forced to put two of them (Sungold Cherry tomatoes) outside.  Today, they are the healthiest, most robust plants I have... More on this later.