drdawg said: Vermiculite holds lots of moisture. I no longer use it at all though it can be successfully used in starting seeds.

Either seed starting or storage of bulbs is the only way I use it now. Aside from holding too much moisture, in addition it can mat or cake down in the soil which is not a good thing for something used to provide aeration in a potting mix.

William said:Sandy, I actually have never used vermiculite at all, so not the right person to ask. However I respect both David's and Ken's thoughts very much and their opinions here make much sense to me. I have sand for free, but even if you would need to buy some. it would be a lot cheaper than vermiculite as that is usually a very expensive product, at least here it is. Just make sure there isn't any salt in the sand and you will be fine. I heard the recommendation to taste the sand to make sure there is no excessive salt in it, but I'm not prepared to go that far myself

Thanks William. And I respect you.

Your comment about sand is spot on. I usually wash, drain and dry mine. I usually use a bleach solution. Depending on the application, I sometimes boil it.

If you buy the products called Soil Cover, they are very clean. And very expensive! Much of the sand sold in my area is dredged from the Missouri or Mississippi and only the Lord knows what might be in there. Very cheap though.

I use small bark nuggets or shreds on the soil surface to reduce humidity. They also help support spindly stems without keeping them wet. I screen the bark myself to remove fibers and dust, which would wick water and keep the air near the stems humid.

My first thought when I saw those seedlings was "lights are not bright enough". If you can shoehorn one more CFL in there, like a spotlight bulb, aim it at just one tray and see if that tray comes up much less leggy. The comparison makes it a controlled experiment. (This might be an experiment for next year, if the spindly ones survive.)

They might also be too warm. Brassicas would prefer cool air after they emerge - maybe 60-65F. They would prefer 60F to 90F!

I agree that running a small fan intermittently will strengthen the stems. Even if it is just a few minutes a few times per day. Anything that makes them wave around a little will strengthen the stems.

Rick, although I agree that light could certainly cause spindly seedlings, this happens for me even when I direct sow outside in direct sun... (plus, I grow all kinds of seedlings that don't have a problem, just that the Brassicas have some of the root showing above ground that doesn't really support the plant. Even then, the plants do eventually grow just fine; but I usually need to give them some support.

Weedwhacker said:Rick, although I agree that light could certainly cause spindly seedlings, this happens for me even when I direct sow outside in direct sun.

????

One specific species?

I have never had legginess when planting directly outside unless I plant a sun lover in too much shade.

Funny how memory works, but as Rick mentioned temperature I just remembered an additional method to prevent leggy seedlings in greenhouses that I learned about a long time ago from a commercial greenhouse owner. There is a method called negative DIF that is effective on many plants to prevent plant stretch. With this method the aim is to keep night temperatures higher than day temperatures. There is also a variant of this called "Cool Morning Pulse" in where you lower the temperature at dawn for a few hours.

For more details, I'd suggest to look here: http://www.pthorticulture.com/... . There is also a small table that shows what plants responds best to this and a few other suggestion to control plant height as well. The problem that I can see is that it costs a lot to warm greenhouses and small greenhouses also often get warmer during the day than huge commercial ones, but keeping this in mind one at least has an additional tool to work with.

An interesting idea would of course be to implement this indoors as warming costs and excessive heat during the day would be less of a an issue. Could be interesting for those with a dedicated growing room.

If I ran the furnace at 85 at night and 60 during the day, my DW would kill me. But with heat mats, perhaps we could come close.

In a GH, they would almost have to run an AC during the day. No?

I've probably somewhat misrepresented the problem I have with Brassicas -- they aren't so much spindly as they just grow king of weird, with some of the root staying (or pushing out) above the soil line, causing the plants to flop over.

David, but surely you must agree that growing the best possible plants would be worth that small sacrifice

Otherwise I was thinking it would be easiest if one had the possibility to adjust the temperature for the grow room individually - no need to to change temperatures for the whole house. But I understand this is not always possible.

One important thing to note is that even if on doesn't manage to achieve negative DIF, lowering the difference between day and night temperatures still seems to have good effect according to figure 1 in the link i posted above.

I do believe most greenhouse growers interested in this would probably use the related "Cool Morning Pulse" variant as it would be a lot easier and cheaper to use. I'd quote from the above link: "This method consists of lowering the morning temperature 3-6˚C (5-10˚F) for 2 to 3 hours at dawn. This is the time of day when stem growth is most active." Now this certainly seems achievable during the early growing season, just using regular ventilation, as the temperatures usually are at their lowest then anyway. It would also imply that you during the night kept the greenhouse temperature at 3-6˚C (5-10˚F) above the anticipated temperature the following morning and that would of course still cost you.

I don't have a grow room and I don't heat my greenhouse except in case of emergency late in the season. However I sometimes move my plants from the greenhouse to indoors for the night when cold weather threatens. Then I throw them out in the cold the following morning which would also be giving them a "Cool Morning Pulse". This is negative DIF on the cheap, although I haven't thought of it as such previously.

William, that is the kind of thing I was thinking of. Also, just plain cooler temps all day and night should produce slower and stockier growth for some species. And I know that all Brassicas I grow prefer cool.


>> I've probably somewhat misrepresented the problem I have with Brassicas -- they aren't so much spindly as they just grow king of weird, with some of the root staying (or pushing out) above the soil line, causing the plants to flop over.

I guess it was hard for that to sink into my brain. Now I see what was meant by "maybe sow them a little deeper".

I wonder whether chunky, gritty mixes promote or prevent that tendency compared to fine, peaty mixes?

"I wonder whether chunky, gritty mixes promote or prevent that tendency compared to fine, peaty mixes?"

Good question... I wonder if that would make any difference. (I just use Miracle-Gro potting soil for my seed starting, or occasionally vermiculite, especially for very small seeds.)

Maybe I saved a bag of peaty Miracle-Gro seed start mix too long, or abused it during storage, or something. My bag was like a bag of peat dust, and it would have retained too much water and zero air even if I was not an over-watering idiot.

As far as being gritty or well-aerated - once wet it was like pudding.

Around the same time I wised up to TRYing to overwater less, I also started making much coarser seed-start mixes using screened bark shreds and ProMix-like "professional" soilless mix. And sometimes a little crushed stone or the coarsest sand I can find.

And then I added the wrinkle of a layer of cotton flannel under my propagation trays.
(Absorbent felt should work as well, or an old towel or Tee shirt.)
Now, I can "bottom water" without clogging my bathtub's drain with mud, bark and grit.
The absorbent pad sucks any perched water right out of the prop cells, and re-directs it to any extra-dry cell.
And holds enough water to supply every cell for 1-2 days.



http://garden.org/ideas/view/R...

I no longer kill tray after tray of seedlings. But is it the coarse mix, the cotton flannel, or TRYING to do less over-watering?

Seriously... growing cabbage plants cannot be all this complicated

William said:David, but surely you must agree that growing the best possible plants would be worth that small sacrifice

But of course William!!

When it comes to my plants, whatever it takes I usually say!

Negative DIF and "Cool Morning Pulse" are interesting. I want to give it some thoughts. Since I am not a GH grower, I was unfamiliar.

cheers

Weedwhacker said:I just use Miracle-Gro potting soil for my seed starting

And that works well for you?

DavidLMO said:

And that works well for you?

I know -- everyone seems to hate that stuff... but yes, it works for me, for whatever reason (and it's readily available). On the other hand, I've tried "real seed-starting mix" and had terrible results. I suspect the reason is that I tend to be an under-waterer, whereas most people seem to report problems related to over-watering.

Weedwhacker said:Seriously... growing cabbage plants cannot be all this complicated

Besides seedling starts ( Cabbage White Groupies )

re: Miracle-Gro potting soil

Weedwhacker said:

I know -- everyone seems to hate that stuff... but yes, it works for me, for whatever reason (and it's readily available). On the other hand, I've tried "real seed-starting mix" and had terrible results. I suspect the reason is that I tend to be an under-waterer, whereas most people seem to report problems related to over-watering.

I always wondered how people used those peaty mixes without drowning and rotting seeds.

I guess you add water the way my dad added vermouth to martinis: let the soil SEE the water from about 12" away. Briefly.

"Hi. My name is Rick. I'm an over-waterer."

Thanks for the acorn, Rick!