Cos lettuce grow-off followup

A while ago I started a cos lettuce grow-off between three different types of container growing. And how did it work out? Well, all three methods ended up working pretty well, although my possibly biased impression is that the lettuces planted in the soil-less mix (50-50 vermiculite and perlite, left in the pictures) and Mexican style SWC (right in the pictures) both seem to do slightly better than those in he 1 part perlite 4 parts potting soil mix (in the middle). The pictures below were taken about 3 weeks ago. This is not a completely scientific comparison since I have been harvesting lettuce from them.

Cos lettuce from above

Soil-less mixture far left, 20/80 perlite/potting soil in middle, Mexican style SWC far right.

Cos lettuce from the front

Soil-less mixture far left, 20/80 perlite/potting soil in middle, Mexican style SWC far right. Notice the smaller cos plants growing in the windowsill. Even in 7.5 cm pots a number of edible leaves were yielded :)

The trouble with hydroponics

About a week ago the lettuces in the soil-less mix suddenly appeared quite limp and weak. I measured the Ph of the nutrient mix in the reservoir and it was about 4.8. A bit low! For interest sake I checked the Ph in the soily container, and it was similarly low, but the lettuce growing there was fine. After leaching with a good quantity of fresh water, the lettuce in the soil-less container perked up almost immediately.

This demonstrates quite nicely the vicissitudes of 100% soil-less hydroponic growing. You actually need to manage the nutrient Ph etc. actively, since you don’t have the luxury of the soil buffering the Ph for you. I had been watering both the soil-less and soily container using hydroponic nutrient solution without bothering to regulate the Ph in the reservoir, but trouble only arose in the soil-less container. This is not an indictment of hydroponic growing, but simply an observation that if you go hydroponic, you really do need to do it properly :)

Happiness and Joy

I must say that I have been pleasantly surprised by the quantity and quality of the lettuce that I have been able to harvest. I have made several (10+) salads already, and they still seem to be growing well. It seems that Cos lettuce grows even more easily than rocket :)

Cos lettuce grow-off

Some time ago, I saved seeds from cos lettuce plants that had bolted. Back then, they did not grow so well, but they did produce a heck of a lot of seed. I decided to do a bit of a grow-off by different methods. The first two contenders are 7l self watering containers, the one filled with 1 part perlite to 4 parts Culterra potting soil, the other a 50/50 mixture of perlite and vermiculite. The third is a low-budget kinda-SWC a la Mexico.

Why the grow-off?

The 1 part perlite (or sometimes with 1 part vermiculite also) with 1 part potting soil mixture seems to be the de-facto standard for SWCs. I find it somewhat unappealing since the potting soil is good for a max of 2 years, or usually just one growing season. The (somewhat expensive) perlite that is mixed with the soil is also discarded, since there is no easy way of recovering it. The purely soil-less vermiculite/perlite mixture is very inert, and can actually be sterilised and re-used many times. The Mexican style SWC really only uses organic waste material that is available for free, so that seems quite attractive too. Seeing which one yields the best crop is of interest too!

Special needs

The vermiculite/perlite mix is completely inert, hence no normal soil mechanisms. This means that hydroponic nutrients need to be used. They are surprisingly cheap from the gro-shop. They are also the cheapest place for perlite that I have found so far. For the Mexican style container, you need to save some urine! Well, you could use other fertilisers, but I thought, you know, what the hell :)

So far

I germinated about 20 seeds, and then selected the best seedlings. I planted three in each of the 7l SWCs, and 5 in the somewhat bigger Mexican style SWC soon after the seedlings formed their first pair of true leaves. Since the Culterra potting soil includes a slow release fertiliser, I decided not to add nutrients to the soil/perlite SWC to start with. I used maple leaves from my back yard to fill the bottom part of the Mexican SWC. Since I also used the Culterra soil for the Mexican style SWC I have not added any additional urine yet. I say additional since I did use some urine for the initial wetting of the maple leaves before I added the soil on top. The nitrogen in the urine is useful for starting the decomposition of the leaves that should be going on below the soil.

All three Cosses in a row
Cos lettuce in 7l SWC with 1 part perlite to 4 parts potting soil mix
Cos lettuce in 7l SWC with 50/50 perlite and vermiculite mix
Cos lettuce in Mexican style SWC

About 60% of the volume is dead leaves, the rest is filled with potting soil. Aparently the leaves below should turn into suitable soil to use next year, so I should not need the potting soil again.

In the pictures I tried to take the close-ups of all three containers from about the same distance. Since the Mexican SWC is somewhat larger than the other two, it does not quite fit in the frame. So far (about 3 weeks after planting out the seedlings) the Mexican container and the soil/perlite container seems to be doing somewhat better than the vermiculite/perlite container. All the seedlings look quite healthy though. I think the slower growth in the vermiculite/perlite SWC may be because I started out with a very weak hydroponic nutrient mix, while the seedlings in the other two containers benefit from the included fertiliser in the potting soil. I’ve recently put a stronger nutrient in, so we’ll see if that evens things out a bit.

Sharing, Caring and Spider-mites

It feels nice to give, and I got the feeling by donating one each of the tomato, bell pepper and origanum seedlings/cuttings metioned before to a colleague. The garlic chives are also doing better; intially it seemed like only about 4 of the seeds I planted had germinated, but a couple of warm days seems to have brought the total to 10. Perhaps I’ll be giving some of them away too :)

Spider Mite Woes

On a less positive note, my black eyed Susans have been attacked by spider-mite. These little buggers are quite vicious and hard to get rid of. Part of the problem is their very short life-cycle, which frequently leads to resistance against pesticides. Luckily Ludwig’s organic pesticide that I have mentioned before seems effective. I applied it on Saturday (2010-02-20) night, and the following morning the little red specks previously visible on the leaves had changed to black. Interestingly, the concentration of Ludwig’s spray recommended (by the included instructions) for spider mite is much stronger than for just about any other pest, and you also also need to be sure to completely coat the top and bottom sides of the leaves.

A follow-up application will be needed to take care of new hatchlings as the pesticide does not damage the mite eggs. Will probably do that tomorrow night or perhaps even morning, since high temperatures (like Stellenbosch is currently experiencing) leads to a gestation period of as little as 3 days. I saw another organic spider mite specific insecticide in Stellenbosch’s Builders Warehouse Express which claims to be effective against the eggs too. Supposedly it also results in in less colateral damage, but it was quite expensive. I decided to give it a skip.

Yesterday, while collecting herbs for Sunday lunch cooking, I saw that my flat-leaved parsley also seemed to have spider-mites. Since it was next to herbs I wanted to use immediately (Ludwig’s requires you to wait 48 hours after application before harvesting edible food) I squashed them between thumb and forefinger, and tore off the most badly affected leaves. The very flat leaves of the parsely don’t seem to mind the pressure, and there were few enough leaves for it to be manageable.

Seed Collecting

It takes quite a bit longer for the seeds on plants that have bolted to become harvestable that I had imagined. Today I collected some pods from a basil plant that has gone to seed. It seems like it took forever for the pods to turn brown after the petals have droped. Even now only a fraction of them have gone brown.

I’ve been waiting similarly long for a the cos-lettuce that bolted after an aphid attack to produce seeds. Yesterday I got a bit of a surprise when a guest looking at my garden pointed out the Dandelion like parachute balls that had formed on this plant. And attached to the little parachutes were litte seeds! Yay!

I placed the collected seeds in labeled envelopes for storage. They shouldn’t stay there for too long, since I hope to plant them out soon.

The End

I’m getting better at not blogging during times of day that I should be sleeping! In any case, I also wanted to talk about some of my more recent self watering container experiences, but this post is getting too long. But don’t fret, that news will come in the near future :)

Making Amends and Other Exciting Updates

Quite a busy gardening day! In fact, probably my only whole day spent gardening to date :) In part it was sad, since I had to admit to earlier mistakes and throw out my tatsoi and pinokio cos lettuce, neither of which yielded anything. This allowed me to make amends by amending the terrible soil that I think resulted in my lettuce no-shows. I also finished building a 50l self-watering container to plant rocket in, and started my dry-herb container. To top it all off, I planted tomato and garlic chive seeds.

Lessons about soil

When I first started gardening (not too long ago) I had the attitude that potting mix is expensive, and that I should water it down, so to speak, using normal soil. I felt I was on solid ground, since my GF’s mother plants all her containers using exclusively garden soil with some success. Initially this worked for me too, but later cought up with me.

The thing is, my GF’s house has very nice soil that is fairly light and well airated and full of organic matter. When I started I took a bag of soil from her house, and mixed that with the potting mix. Later, when I adding more pots, I started using soil from my flat complex’s beds, expecting the same results, but oh-no. Not a good idea.

The Dead Rosemary Bush

After killing a rosemary bush (which is quite hard), I found that the bottom two-thirds of the pot was pretty much a solid lump of clay, completely preventing drainage. Mystery solved there. So, I think, let’s just remove half the soil, and mix it down with more potting mix. Certainly that should be good enough. Well, it was better, but after a while the new rosemary plant was going nowhere. By now I’ve come to respect the importance of drainage for potting soils, and realised what was going on.

Of Al and his Mixes

There is a regular container mix guru on the gardenweb forums known as Al. What he has impressed on me is the importance of good drainage and aeration for pot plants. As he puts it, on a scale of 1 to 10 where 1 is gardening in regular soil and 10 is hydroponics, container growing is about a 7-8.

When gardening in the real earth there are natural processing going about the conversion of organic matter to plant-nutrients (bacteria, earthworms), processes keeping the ground aerated (earthworms, burrowing animals, etc) and probably a hundred other processes doing a hundred important things I’m not aware of ;) In container gardening you can’t depend on them.

His chief aims when choosing a potting mix is that it is

  1. Well aerated. Surprisingly, plants actually need to obtain most of their oxygen an CO2 requirement via their roots rather than their leaves.
  2. Durable. Some components used in a potting mix can decompose and turn the mix into “soup” that kills aeration.
  3. Well drained.

Al has some mixes that he prescribes, and also goes to some length to explain the rationale behind his mix-design. He also discusses container fertilisation.

Paying for Sins Past

Well, as I mentioned, the new rosemary bush also started looking not so good. After the first death I took care not to over-water, and occasionally tilled the soil bit, but there is only so much you can do in a pot!. For my efforts the top layer of soil was in reasonable condition, but as I went deeper I found pretty much a replay of the soild conditions implicated in the first rosemary death, including a nice rotten-egg smell in the bottom layer. The rotten smell indicates a complete lack of oxygen, resulting in anaerobic bacteria doing their stinky thing.

And so, I decided, enough messing around. Time to get rid of all my bad soil. Out came the old rotten soil, and in came fresh Culterra potting mix. I hope Rosemary enjoys her re-decorated home. An added advantage of using proper potting mix is that it is much lighter than garden dirt, making it much easier to move pots around.

I also ripped out the pinokio Cos Lettuces that I planted some time ago. After going absolutely nowhere since I first planted them, they started to bolt without having given me a single usable leaf! Also planted with them was some tatsoi that also suffered from going nowhere. I remembered doing some dodgy soil-mixing with that container, but was surprised when the soil appeared to be pretty much pure potting mix. As I dug deeper, however, I soon came to a solid-blocked layer of clay-soil again. Ahah. I planted two of the bolting lettuce plants in another container with the hope of harvesting some seeds, so perhaps I will get something for my efforts in another generation of plant!

Planting out Rocket Seedlings

In the 50l self-watering container I built today, I planted out some of the rocket seedlings that I raised from seed. I also removed a wild rocket plant from another pot that had bolted before making hardly any leaves. I think the problem with that rocket was that it was in the small pot at the nursery for way too long. I was about to throw all of it away when I saw that it actually consisted of several separate plants, and that a couple of them looked like young plants and were not bolting. I planted those out for the joke too. I may have been a bit hard-handed in removing them from the other pot, so we’ll see if they make it.

What was interesting to note was how quickly the seedling roots grew down, through the bottom aeration holes and into the water resevoir! I hope that does not cause problems later.

Planting out Marigold Seedlings

I planted Marigold seeds at the same time as the rocket mentioned above, and planted a couple of them out into the pot vacated by the wild rocket. Their roots had grown even more crazily than the rocket seedlings’. The roots of some of the seedlings were probably 20 times longer than the seedling itself! I may have broken some of them off in the process of transferring the seedlings, so I’m hoping for the best.

Bellpepper seedlings.

Lo and behold, the seeds I saved from a store-bought pepper have germinated. Now we must see what we get!

Dry-herb Container

By dry I mean herbs that like dry growing conditions, such as rosemary, thyme and origanum. I re-purposed the 50l basin-type container vacated by the cos lettuce (I think I’ll try a self-watering container next time I grow lettuce) for this. To make the soil even better drained, I added (what I hope is) pine bark-fines to the potting mix, making up about a third of the mix. I haven’t come across bark-fines at local nurseries yet, but the bark sold as mulch usually has a fair portion of fines. By fishing out the largest pieces by hand, a reasonable mix can be had.

The reason I hope it is pine is that some other tree bark can inhibit growth; I bought at Cape Garden Centre on the R44, but they could not tell me if it was pine or not. It looks like pine though. Earlier the day I was at the Stellenbosch Builder’s Warehouse Express where they were certain that their product was pine, but I did not buy it then. Later when I realised I wanted it, they were closed, and I had to go the the Garden Centre.

I re-planted another rosemary bush in this container; this bush was previously in the same container as my basil and chives. Since the basil and chives like more water than rosemary, replanting seemed like a good idea. I also planted a new thyme plant that I bought at a supermarket. I have a thyme plant in another container, but did not want to re-plant it at this time. I will probably add origanum if/when my cuttings take off, and then see if it makes sense to add anything else to this container.

Garlic Chives and Tomato seeds

I planted about 10 garlic chive seeds in the 2l self-watering container vacated by the rocket I planted out today. I also planted some Season Red tomatoes. These being hybrid seeds, you only get about 10 or so seeds in a packet. In fact, they package the seeds within another little paper envelope inside the seed-packet. For now I’m only planning to grow one plant, but just in case I planted four seeds into 5cm pots. with the Master Organics Super Premium Potting Mix. I’m keeping them wet from below in a tray. If they all germinate successfully I’ll decide what to do with the extra seedlings.

The End

Phew, what a day. I hope I can one day pick the fruits of my labour :) It’s getting a little late, so Good Night!