Summertime

Summer is officially here and so is the heat! The garden is soaking up the sunlight on these ultra-long days and growing fast.

In Fields 2 and 3 are potatoes, garlic, onions and various cover crops. Nearby are the two greenhouses. The old greenhouse in front is home to the tomatoes and the new greenhouse behind is still where seedlings mature before moving out to the field as transplants.

Through the roll-up sides of the old greenhouse (put up in the daytime for ventilation and put down at night for warmth) you can see the tomatoes are getting tall.

Inside view of the tomatoes growing up the string trellises.

Tomatoes!

In Field 1 are the peas, broccoli, eggplant, radishes, lettuce, spinach, bok choy, kohlrabi, beans, turnips, tomatoes, peppers, eggplants, cucumbers, corn, carrots and beets. Most of the mid-late summer veggies are still small but growing by leaps and bounds every day.

Lettuce is one of the first late spring veggies to appear and we've been eating it for the past couple of weeks. It's so exciting to start digging into fresh garden produce after a long winter of root cellar veggies, preserves and pickles and the few things we buy at the grocery store. I'm never disappointed at the amazing taste of the food our land gives us.

Veggies aren't the only thing growing at the farm this season. Baby #3 is due to arrive in two months with all my late summer favorites like corn, peppers and zucchini.

The kids have started their own little garden in the front near the house. They check daily on the progress of the cherry tomatoes, beans, peppers, cucumbers, peas, carrots and lettuce. There's also a small corn plot nearby.

Stay cool during these sweltering days! Visit our CSA page for info on our local pick-up options.

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Spring snapshots

It's a busy time as the weather is finally settling. The greenhouse is bursting so here's a quick tour of what's growing.

Best seats in the house (on the heat storage tank): tomatoes, peppers and some new seedings.

West benches.

East benches.

The onions are ready to transplant.

Tomatoes are rarin' to go! I have one batch transplanted in the ground in the old greenhouse and these ones are ready to get out there once the nights warm up a bit.

Early beets.

The first wave of broccoli is in the field, here is the second.

Some trays of lettuce, also ready to get out to the field.

OK, back to work!

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Greenhouse Solar Heater

One season-extending upgrade I've added to the new seedling greenhouse is a solar heat absorber. The idea is to replace part of the south wall with something that will primarily heat the inside air. I used a completely passive design - this system requires no power to run, other than direct solar heat gain from the sun. This basic design was popularized during the energy crisis in the 70s, so it is easy to find reference material to help design it.

I started out by building the south knee wall "inside out" - that is, I tacked the plywood on to the inside of the framing, instead of the outside. This creates a cavity where the absorber will be built. In the picture below, you can see the cavity as well as some circular ducts I drilled out for cold air in (at the bottom) and warm air out (at the top).

Next, I added two layers of black aluminum window screen, separated by a small spacer. It is held in place with an additional spacer strip. The screen is attached to the outside of the framing on the top, and to the inside below, so that the screen is actually held at an angle in the cavity. The purpose of the angled fastening is to force the air though the screen as it flows through the system. Cold air enters through the lower ducts (outside of the screen) and is forced back through the screen on its way up towards the upper ducts. Since the black window screen heats up when the sun shines on it, natural convection keeps the air flowing during the day. When the sun goes down, the convection shuts down and the collector acts much more like an insulated wall than like a window.

Finally, the cavity is glazed with corrugated pvc. I chose this material for a couple of reasons. FIrst of all, it is just about the cheapest solid glazing available. The corrugations create more turbulent flow in the absorber which is supposed to increase efficiency. Lastly, I was not sure about using the brittler, more expensive polycarbonate where it might be exposed to huge temperature variations.

Here is the view from the inside. I've just covered the ducts with scraps of screening. Mainly this is to provide a backstop for the backdraft dampers, but I also felt like it might be necessary to keep the mice and other varmints out of the space.

And here is the system in action! The backdraft dampers are thin pieces of polyethylene plastic taped up above the ducts. At night (or on a very cloudy day), there is not enough airflow to push the plastic out so reverse flow is prevented (in which air would be cooled by the collector).

The day I took this photo was nice and sunny but with weak winter sun. Still, a steady stream of hot air pushed the dampers open. The temperature was probably in the 120 degree F range (although I didn't measure exactly).

There are many more sophisticated designs out there, but I put this together without really adding any new pieces to the plan with the exception of window screen and glazing. I'm pretty happy with the results so far - we'll see how it does in the early spring when I really need the extra heat. Next up: a solution for how to store heat in the structure overnight.

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Greenhouse Progress

The new greenhouse is progressing nicely. Two layers of plastic are up on the hoops. This is a change from the last one which only uses a single layer. The advantage of doubling the plastic is that the space between the layers can be inflated with a small fan. This creates an insulating air space and also maintains tension on the plastic which (in theory) reduces stress on it from wind and other weather.

The south end wall is framed and is now glazed with triple layer polycarbonate, which has decent insulating properties while still letting a good amount of light through. Here we are working on a ventilation window which is now covered with polycarbonate. Overheating is a significant concern and I've decided to skip the roll up sides for this one so it's important to be able to move air through the ends

The north end wall is framed and sheathed with plywood. I'll probably add some rigid foam insulation on the inside here. It's quicker to cover the end with clear plastic but very little light comes in from the north so a semi-insulated wall will provide more frost protection without much of a downside.

I hooked up a fan through a length of dryer ducting to test out the system. Because I'm planning on using a solar panel to power everything, I used a 12 volt computer fan as the inflator instead of a specialized greenhouse fan. It's not perfectly suited to the job but it seems to work just fine. I was able to measure the current draw during my test (about 280 milliamps, or about 3.5 watts) as well, which will help me size the solar system.

Here's the view from inside with the fan running and the polycarbonate in place. The inner layer balloons inwards a bit and the outer layer curves out. It took a minute to inflate enough to be noticeable so at first I thought it wasn't working but once I let it run for a bit it looked great.

Stay tuned in the weeks to come for more updates about the solar panel setup, a passive solar heat absorber, and my thermal battery seedling bench.

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Greenhouse 2

Another fall, another offseason building project! After the success of our first year with our greenhouse, I've decided to build a second one. The new one will be smaller and dedicated to seedlings so that I don't end up trying to juggle space between seedling benches and young plants in soil. This way I can have a separate space just for seedling benches and I don't have to worry about when to move them aside for bed space.

I'm also making the new greenhouse warmer than the other one in a few different ways. One is to make the walls a double instead of single layer of plastic. Another is to replace the roll up sides (used for ventilation on hot summer days) with non-movable insulation to retain heat.

Other designs for added warmth are still in progress - like a water tank for the seedlings trays to sit in that will circulate water warmed by the daytime sun overnight to keep temperatures steady. I'll post more updates as this project moves forward!

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Fall Greenhouse

Our greenhouse is getting close to its first birthday. Happily, we've gotten great use out of its first year. It serves multiple purposes depending on the time of the year; right now it's mainly being used to extend the growing season of late summer veggies like tomatoes, sweet peppers and eggplant.

The side vents are open in the day and closed at night in the spring and fall.

It's pretty gratifying to see such healthy looking tomatoes in the greenhouse at a time of year when the field tomatoes are dying off. The next step will be some experimentation over the winter with cold tolerant veggies and possibly another, larger greenhouse in the future.

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Eva Mae Farm