Category Archives: Tools

Resources for Growing Quinoa

Here are my go-to sources for quinoa growing supplies.


Soil and Compost


Hand Tools




Danger of frost has passed for peninsula gardeners.

One of the challenges that any gardener faces is deciding when to plant seeds in the new year. Here in the San Francisco Bay Area, and in particular the peninsula, we are very fortunate to have extremely moderate weather and so it means that we can start the planting season very early. But how early?

The one danger that we face is that we can get frost in February. Frost is particularly damaging for certain types of seedlings, and so it’s important to consider. In fact early last year we had about a full week of evening frost. I remember this vividly because I had potatoes that were about to go to maturity and so I was out there every night covering them, and out there every morning uncovering them. I know that people’s memory of weather can be unreliable and so it got me wondering if there was good historical data out there. It turns out that there is.

A few years ago I really got into analyzing weather data. I discovered a UC website that had free, rich, downloadable set of climate data for various spots in California. And with the help of Excel I did a lot of analysis on it. At the time I was just doing it for fun but now as a gardener I can look back at the analysis that I did and pull out some very important information.

Frost danger climate chart SFO RWCHere is a chart of climate data from the year 2000 to the year 2010 for the San Francisco Airport and a spot in Redwood City. The red dots show the high temperature for the day and the blue dots show the low temperature for the day. The green dots are precipitation. For the purposes of deciding when it’s safe to plant, let’s focus on the blue dots.

Although technically 32 degrees Fahrenheit is freezing temperature, I personally start to get concerned when the temperature is below 34F. And so I have drawn a blue dotted line showing approximately where 34F it’s. And you can see that from around the middle of February onwards, the nighttime temperatures in this 10-year period have never dipped below 34F. So this gives me a fair amount of confidence with respect to going and putting seeds or seedlings in the ground.

I would say that mid February is a fairly safe guideline overall. Granted, it depends on what you’re planting, but I feel comfortable that I can plant from now going forward and I won’t have frost problems. Keep in mind that some vegetables need much higher temperatures than 32F in order to work, but the point here is that frost creates special problems for many food crops.

One might reasonably ask what happened to the data from 2011 to 2014. The problem I ran into is that the University of California website stopped published the data I was using. Fortunately somebody at the UC extension office was able to refer me to a data source from Utah State University which for some reason has California climate data. (Thank God.) And so if I wanted to I could work that data into my spreadsheet and update my chart.

In any case I just downloaded fresh data and did a quick spot check of weather data from 2011 to present. What I found is that in 2011 there was a late frost from 2/26 to 2/28. And in 2013 there was one night of frost on 2/20. To find the previous late February frost, I have to go back to 1996, and before that, 1990. So while historically there is a *chance* of frost in late February, it’s rare.

The key point I want to communicate here, besides mid-February being a safe time to start planting, is that there is wonderful free data available, if you know where to look, and we can learn a lot from it.

How I Built My Seedling Flats

B43mXNVCIAEU9fQAn important part of Grow Biointensive is starting your seeds in flats (wooden boxes), and then transplanting the seedlings when they are hardy enough to reliably survive. If you don’t want to build them yourself, you can always buy them from Bountiful Gardens. But since I needed 16 flats, the prospect of spending ~$300 + shipping on flats wasn’t palatable. Besides, where possible I really wanted to learn how to build basic growing infrastructure, such as flats.

Here’s the thing, if you’re a carpenter or woodworker or general handyman, you’ll say “OK so you’re making small wooden boxes. Very easy.” But if you haven’t done this kind of thing before, like I hadn’t, it can be daunting. Nonetheless I decided to give it a try, and it went fine! My intent here is to share with you my learnings and opinions, to try and take away some of the mystery of it, and also to help you get a better end product on your first try.

The High Level


  • IMG_20141214_194854lg (NXPowerLite Copy)For the sides: untreated Redwood fence board, ripped in half length-wise to make 3 ½” high sides. I used this wood: FSC ConCom Redwood Flat Top Fence Picket (11/16 in. x 7-1/2 in. x 6 ft).
  • For the bottom: Redwood bender board. I used this wood: Benderboard Redwood (1/8 in. x 3-3/8 in. x 8 ft.
  • Cedar would also work fine.


  • 14” x 11”
  • This gives you five x 14” pieces per half fence board, or seven x 11” pieces.
  • On the 11” width, it means you can nicely space the 3 bottom bender boards, get just enough of a gap between them for drainage, and not have to rip (cut in half length-wise) any of the bender boards. If your bender boards are a slightly different size, adjust the width accordingly.
  • The resulting flat is about 65% the size of a full flat, and so not too heavy to carry.


  • “Drive Straight” self-drilling lath screws, 1 ¼”.
  • Pre-drill 3/32” for attaching sides; no pre-drill for attaching bottom bender boards.
  • One screw per side of board works fine, for both the sides and the bottom. The bottom benders will warp less with 2 fasteners per side, but in general 1 is working fine for me.


  • Table saw to rip fence boards length-wise.
  • Miter saw to cut fence and bender boards to length.
  • Safety equipment for using the table and miter saws.
  • Drill to pre-drill side board holes and screw in fasteners. If you have two tools, you can avoid needing to switch bits.
  • Tape measure, pencil, carpenter’s square.

Fair questions

Why not use bender board on the sides, like the HTGMV book says?
I did this and broke several in the first year. When it’s full of soil and you tug it on a bender board side, it’ll snap. If it happens at the wrong instant, you can lose a full flat of seedlings. Not worth the hassle.

 Why not make full sized 11″ x 23″ flats, as commonly used on Ecology Action farms?
In my experience full sized flats are extremely heavy, especially when the soil is wet. It’s easy to drop heavy flats, destroying the seedling, or even worse, to get a back injury from lifting the flat.

I also think the full flats are more brittle because of the relationship of weight to length, but I haven’t used them much. My 6″ deep half flats are the same weight as a full 3″ flat, and I have to be super careful when I move those around.

These 65% flats are a nice balance of size and weight. If you wanted an even lighter box, consider a 11” square box, which would roughly be a half-flat.

Do you really need to pre-drill the sides?
When I made my first batch of boxes, I was cracking about 1/3rd of the boards I was screwing into. It’ll depend on how fresh your wood is, too. It’s disappointing to have wood crack, and so I decided to take a moment to pre-drill using my old screw-gun, which resulted in zero cracking. The dryer your wood is, the more important it is to pre-drill.

Do the self-drilling screws really hold?
Yes, holding power hasn’t been a problem at all. The bigger issue is if a board cracks, and the self drilling screws are less likely to do that.

Do you need to treat the wood?
I haven’t treated the wood and so far it seems to be holding up well. If you know how to do it, you could. There is some skill to doing it safely since the treatments can be highly flammable before drying, and any rags you use in the process need to be taken care of properly. I haven’t done it, but looked it and decided to go without for now.

In More Detail

Sourcing Wood

If you can get access to salvaged wood, and it’s in decent condition, then use that. But don’t use it if it’s been exposed to chemicals, or painted. I used a number of hard old fence boards from a neighbor, and found that as long as I predrilled my side holes to avoid cracking, it worked well.

If you’re buying your wood, I recommend finding one reliable vendor to buy from. In particular for your bender board, you’ll want to consistently use the same width. I’d personally rather not  try to rip a piece of bender board to be narrower and so the width of the bender board becomes a driver for the dimensions of the box. I haven’t tried to rip bender board, but it strikes me as the kind of thing where it’s easy to have a piece break off and come flying at you off of the table saw.

Type of Wood

You’ll want to use a wood that is naturally resilient to weather, such as Redwood or Cedar. I advise against using chemically treated wood because it’s easy to see those chemicals getting into your soil, into your plants, and then into you. It’s just not worth the risk.

For the sides of the box, I’ve been buying 11/16 in. x 7 1/2 in. x 6 ft. Redwood picket fence like this one and then cutting it down to the size I need. I’d say you want the wood for the sides to be at least ½ inch thick. Since this is a “less expensive wood” from a “less expensive store” I always have to carefully pick through the pile to find pieces without cracks or other major flaws.

For the bottom of the box, I’ve been buying Redwood bender board like this one although you have to be very careful to get a piece that doesn’t have knots or cracks. Wear gloves to the store and don’t be afraid to search through the pile for the good pieces.


One fastener or two? Up to you. Note drainage gap between boards.

Initially I was using a different fastener for the bottom bender boards and the side fence boards. However after a year of heavy usage, I found that both fasteners were doing just fine, and so there’s no point is using two different kinds, and also no point in spending the money for the more expensive “deck screw” kind.

So I’ve settled on using self-drilling lath screws, 1 ¼” “Drive Straight” which Home Depot sells. On the upside it saves me a lot of time because when I’m attaching the bottom bender boards, I don’t need to predrill and the bender boards don’t crack. I was initially concerned about holding strength, but this hasn’t at all been an issue.

I do predrill the holes for the side fence boards, to minimize the chance of cracking. I used a 3/32” bit and had zero cracking. A 1/8″ bit would probably work fine, but I like to think I’m getting better holding power by pre-drilling with a slightly smaller bit.

I did some boxes with 1 fastener on each side of the side boards, and some with 2. I didn’t see any performance difference, so I’m just going with 1.

I also did some boxes with 1 fastener on each side of the bottom bender board, and some with 2 on each side. I did see warping on some of the bottom benders with just one fastener, but not widespread. Frankly the bottom bender boards are going to fail first anyhow, and I’m not sure it’s worth the extra fasteners. On the other hand, the wood should last longer with 2 fasteners because of less warping. So you’ll have to decide what you want to do.

Assembly tips

IMG_20141214_194705 (NXPowerLite Copy)I found that using clamps made it much easier to put the boxes together. I used a pair of 24” Harbor Freight Aluminum bar clamps that are performing well enough for me with occasional use.

When screwing in the bottom bender boards in particular, set your drill for minimal torque. The bender boards are thin and so it’s easy to drive the screw too far and split them.

Last word: safety

There’s one thing you must keep in mind: cutting wood with power tools is dangerous! Seriously! If you aren’t an expert in this, find someone who is. Keep in mind, though, that many  “handyman” types have terrible safety habits. A good bet is to find places like Woodcraft or Tech Shop that have classes taught by people who are safety conscious, and tend to know what they are doing. Otherwise, there are some decent safety videos to be found on YouTube. Here’s one of someone purposely doing the wrong things, so you can see how scary it can get.

Anyhow, if I haven’t scared you off yet, I hope your flat building is fun and fruitful. If you have any questions, let me know.

How to use Excel to make your garden map

2014 Spring final bed picMany people have asked me to show them how I use Excel to make my garden maps, and so here is a walk-through. The summary is that I simply resize the cells to be square in size, create a border for the bed boundaries, color in the beds using patterns, and then insert labels using Text Boxes. Here is a step by step walk-through.

If you want to jump right in here’s the result: Sample Garden Map.xls

Any version of Excel will work, but for these instructions I’m using Excel 2010. For different versions, the exact location in the user interface may vary, but the features should have the same name.

A.    Resize the cells to be square

  1. Create  a new blank Excel document.
  2. Select all cells in the worksheet by clicking on the “triangle” towards the upper left, between the letters and the numbers.
  3. Right click on column header A and choose “Column Width”
  4. Enter “2” for column width. This maps to 25 pixels on my computer, but anything will do as long as it’s the same as what you put for row height.
  5. Right click on row header A and choose “Row Height”
  6. Enter “15” for row height. This maps to 25 pixels on my computer, but anything will do as long as it’s the same as column width.

Result: Your Excel sheet should now look like graph paper.

B.    Scale the sheet so you can see your whole bed

NOTE: my beds tend to be 4 to 5 feet wide, and so I like to make every square on the sheet map to a 3” x 3” section of my garden. Thus a 4×4 set of squares represents one square foot of the garden. On my laptop, if I scale my view to be 45%, then I can see the full width of a 25’ wide garden bed. You can experiment with the zoom feature to see what the best zoom level is for you.

  1. Click “View” menu and choose “Zoom”
  2. Choose “Custom” and enter “45%”

Result: The “graph paper” will look much smaller now.

C.    Draw the boundaries of your garden bed

  1. Click cell C3.
  2. Hold the “Shift” key on your keyboard, and click cell CX18. You should see the whole range for C3 to CX18 now highlighted.
  3. From the “Home” menu click the arrow next to the “Borders” icon. (The look will vary based on what the last border was.)
  4. Choose the “Thick Box Border” option, which for me is the 8th option down.

Result: There will be a Thick border that defines a 4’ x 25’ garden bed.

D.   Color the inside of the bed with a pattern.

  1. Click cell C3.
  2. Hold the “Shift” key on your keyboard, and click cell AZ18. (Different than last time.) You should see the range for C3 to AZ18 now highlighted, which is half of the bed.
  3. Right click and choose “Format Cells…”
  4. Click the “Fill” option, which for me is the second tab from the right.
  5. From the “Pattern Style” drop down, choose a pattern. I like the cross hatch one, which for me is in the third row, second from the right.
  6. In “Pattern Color” choose the color of your liking. I’ll choose a green. Then click OK.

Result: half of the bed now has a green cross-hatch.

Tip: You can color the other half of the bed to your liking using similar steps.

E.    Add the first crop label for your bed

  1. From the “Insert” menu click “Text Box” and choose “Horizontal Text Box”
  2. On your bed, click and drag to define the size of the text box. You can resize it later.
  3. Right click on the text box you’ve just created, and choose “Font…”
  4. Change the “Size” box to be “25” and click OK.
  5. Click on the text box and enter your text label. I’m putting “Sorghum”
  6. Right click on the text box, and click the “Center text” icon.

Result: Now there’s a label for the bed.

Tip: You can resize it by clicking and dragging any of the corners. You can save time by sizing it wide enough for most of your crop labels.

Tip: You can move it by clicking and dragging the text box’s top or bottom border.

F.     Copy an existing label

Note: it can be quicker to copy an existing label, than to create a new one.

  1. Right click on an existing label.
  2. Click ”Copy”
  3. Right click on your sheet, where you want to place the new label.
  4. Click the leftmost “Paste” icon.
  5. Click on the text in the text box and change it to your liking.

Result: now you have a new label, with the same size and text as your original one.

Tip: Once you map out the areas in your garden, you can simply make a new copy of the sheet for every season. If you keep the outlines of the map the same, then it’s really easy to flip from one sheet to the next, and compare what you planted this season in a given spot to what you planted last season. This is really convenient for planning crop rotations.