long awaited temperature data: second shelf

Here is the data I took of the air temperature of the second shelf while the seedling heat mat was still in place.

The temperature and relative humidity measurements were made by the USB thermocouple every minute for almost two days.  During this time, the timer for the light fixtures was set such that the lights were on from 6AM - 12AM each day.  The heating from the lights is clearly evident in the graph.  This shelf is directly above the shelf containing the electric heater, which was set to maintain 80F by periodically pulsing on and blowing hot air with its fan.

The average temperature during the daytime was 76F and at night with the light fixtures off was 73F.  These temperatures themselves obviously aren't extreme, but considering that the second shelf also receives direct sun for most of the day on sunny days, and that the heat mat is supposed to raise the soil temperature 10-20F above the air temperature, I decided that the plants might be getting too warm.  To solve this potential problem, I unplugged the heat mat.  It doesn't seem to have had any adverse effects so far, and the new seeds I've planted have germinated just fine.

The large increases in relative humidity correspond to times when I watered the trays.  Generally, it's better to have a more humid environment when seeds are germinating and then maintain the greenhouse slightly drier when growing plants so as to decrease the likelihood of rot, mold, or pests.  The Greenhouse Gardener's Companion says that a relative humidity in the range of 45-60% is healthy for most plants, and that relative humidities greater than 80% foster rapid growth of leaf mold and other plant diseases and parasites. 

Since I took these data, I've added vents to the sides of the greenhouse.  I'm pretty sure the relative humidity since then has been much lower than that represented by this graph.  I've placed trays of water on all three shelves to try to help raise the humidity (and also to act as a thermal mass at night), but I definitely think that I'm still losing more humid air out of the slits than I'm gaining through evaporation, which isn't really surprising.  Most commercial and larger-scale greenhouses are able to vent air and maintain high relative humidities through the use of misting devices, but that's a little beyond the scope (and price range) of this first attempt at an indoor greenhouse. 

sick cilantro, bolt, measuring second shelf temperature

I think I've been overwatering the cilantro.  The problem with an overwatered plant, is that except for the soil, it can look a lot like an underwatered plant, or an overheated plant.  Here's my wilty cilantro as of yesterday morning:

There are a lot of yellow leaves, some with brown edges, others with brown stems.  I had been erring on the side of overwatering the seedlings since I'd found some of the tomatoes looking particularly wilted after going more than 12 hours without water.  But I guess that was a few weeks ago, and it's probably time to start spacing out the waterings a little more.  I haven't watered the cilantro since yesterday morning, and am going to wait until at least tomorrow morning, even though the soil now looks quite dry.  Hopefully they'll be able to recover.

During my research into causes for droopy cilantro, I found out some interesting information about the plant.  I'd like to amend a previous post where I jokingly attributed the "Slow Bolt" name for the cilantro seeds I planted to a comparison between how long they germinated and how quickly they grew.  I now know that "bolt" actually refers to an herb sending up a flower stalk.  The flavor of the leaves often changes after it has flowered so bolting is undesirable, and the slower it happens, the better.  Cilantro in particular bolts due to temperature increase, typically when the soil temperature rises above 75F.  I didn't take that into consideration when I chose to plant it on the cooler top shelf and in a tray without a seedling mat, but it's good information regardless.  It also helps me rule out underheating as a cause for the wilting plants.

In other temperature related news, I'm starting to worry that the plants in the second shelf might be getting too warm.  They are closer to the electric heater meaning increased air temperature and are also on top of a seedling mat meaning further increased soil temperature.  I put the USB thermocouple on the second shelf yesterday evening, and am planning on letting it collect data until tomorrow night.  It will be interesting to compare these new data to those I collected previously from the top shelf.

(kind of) new seeds ordered and temperature data soon

I received an email today from the Seeds of Change Customer Service Coordinator informing me that the Herbs de Provence seed collection had been discontinued as a result of the company being unavailable to acquire a number of the included seed packs. The main disappointment of the email was that it removed the possibility that the seeds would be waiting in my mailbox when I got home today. They´d already refunded me the money for the purchase, and so I quickly put it toward six seed packs that should round out the herb garden nicely. Hopefully arriving before I leave for the holidays are:

1 PACK, DILL, DUKAT
1 PACK, MARJORAM, SYRIACA ZAATAR
1 PACK, OREGANO, GREEK
1 PACK, SAGE, GARDEN
1 PACK, ROSEMARY
1 PACK, THYME, GERMAN WINTER

The Rosemary and the German Winter Thyme are both on backorder, but if Seeds of Change ships to me as quickly as they did before, then I stand a good chance of having the rest of them planted and germinating over winter break.
I´ve never grown dill or marjoram before, and this marjoram is supposedly quite different from the sweet marjoram that was a part of the Herbs de Provence collection. They say on their website that the Syriaca Zaatar Marjoram has a flavor that combines the tastes of sweet marjoram, thyme, and oregano, which definitely makes it sound like it´d be interesting to cook with. The other main decision I had in picking out seeds was the dill. They sell four different varieties: Bouquet, Dukat, Goldkrone, and Mammoth. They say that the Dukat is "Delicately aromatic, never bitter or overly pungent. Perhaps the sweetest of all dills. The preferred commercial variety. Stays leafy longer than others." All of those seemed like good things, especially for cooking. I also liked that it´s only supposed to grow to be 18-24" tall, as opposed to the Mammoth which can get up to 5´. The Bouquet Dill was also a smaller plant, growing to be 3´ tall. The website said that this variety was the best to grow for the production of seed, though, and since it is the leaves of the plant that I use most frequently for cooking, this didn´t seem like the best option. They didn´t have any information on the Goldkrone Dill, so it wasn´t really in contention.
In other non-seed-related news, I used a portable thermocouple to monitor the temperature and humidity of the top tier of the greenhouse for almost four days last week to get an idea of how accurate the thermometer and hygrometer are that I have placed on the shelving structure. I also wanted to know how much the temperature varied between sunny and cloudy days, and how much heat and moisture was escaping when I open the flaps for watering and photographing. The quick summary is that the PetCo terrarium meters do a pretty good job of representing the conditions (of at least that shelf) of the greenhouse, and that I should really be keeping the greenhouse warmer, especially at night. I´ll upload the data once I have the graphs processed so that they can be presented in a more accessible form. In response to this new information, I´ve increased the setting of the heater on the bottom shelf of the greenhouse from 70F to 80F (still on the low setting), and that appears to have resulted in an increase in temperature of about 6-8F on the top tier. How it will increase my electric bill, is yet to be seen.