Problems with my large SIP

[Walt B.]

I built 2 large raised bed SIPs (7'x4'). They turned out great (the boxes) but my produce was underwhelming. I live outside of Sacramento (Zone 9A) so it gets hot here in the summer for very long stretches of time (95+ for many days) which is why I went with SIPs in the first place to prevent uneven watering. I used Raybo's 3-2-1 mix (substituting fir bark fines for the pine) to fill the boxes. They wicked perfectly all summer long (according to my moisture meter).

My tomatoes struggled all season (but produced some fruit late) whereas my peppers only grew to about 8" only yielding a few miscolored peppers. Almost every tomato plant suffered from leaf roll all season long. Blossom end rot hit almost all of my early fruit on every plant. I suspect I watered the reservoir too frequently (I was thinking the tomato leaf roll was underwatering) but I also think fertilization was a problem. Considering we get zero rain through the growing season here...... I was thinking the Epsoma Sure Start fertilizer and lime I put in at the beginning never really broke down through the season for the plants.

Here's the specs of my SIPs:

Dimensions: 84" x 44" x 11" (peppers/cucumber box) 24 cubic feet

84" x 44" x 13" (tomato box) 28 cubic feet
depth dimension is of soil media above reservoir

Tomato Box: 3-2-1 Raybo Mix


3 parts sphagnum peat moss

2 part fir bark fines

1 perlite

2 cups dolomite lime per 2 cubic feet peat

6 cups Sure-Start fertilizer mixed in

1 fertilizer strip of one bag Tomato-Tone 5 inches deep down middle


Pepper/Cucumber Box: 3-2-1 Raybo Mix
2 cups dolomite lime per 2 cubic feet peat
6 cups Sure-Start fertilizer mixed in

1 bag EB Stone worm castings

So here's my questions that maybe more seasoned SIP gardeners can help me with:

1) Can you overwater SIP containers by topping them off too often (weekly)? I was under the assumption that the wicking was fairly consistent regardless of how much was in the reservoir.

2) Are organic fertilizers a problem in soilless growing medias considering there is little soil life to break it down?

3) Should I just move to all liquid fertilizers rather than relying on granular fertilizers mixed in at the beginning of the season?