I've grown herbs on my deck in pots for a few years with moderate success. Thyme and rosemary were great. Basil and Dill could have been better. This year I decided to move to a greenhouse thinking that would be idiot proof. Apparently, it is not.

I have very limp basil, the dill is almost dead and the sage, which I normally have no trouble with is limp and wilted. Problem is I have no idea what I am doing wrong. I figure I am eaither watering too much or not enuf, or it is getting too hot in there.

I water once daily (at 18H00) and when I do, the soil is crumbly and dry so it looks like it needs water but that is just a guess as I am a habitual overwaterer. I thought perhaps the greenhouse is getting too hot as I do not open any windows in it (but I could if someone recommends that) but I do not live in a terribly hot part of the world so I am not sure if that is it. It gets to a high of 25C (77F) here so probably about 30C (86F) in the greehouse.

So far I've unloaded over $200 on herb seedlings and they are doing terribly so if someone could tell me what I can do to improve things I would really appreciate it.

As far as symptoms go, all I can really tell you is that all the leafy herbs have really limp leaves that are starting to shrivel. They do not feel dry and crumbly.

Thanks

 

I'm suspecting that your problem is that the poor seedlings are getting a bit too hot. If the greenhouse is outside and in a sunny spot, you might want to increase your venting. Seedlings can be easily "cooked" so it's important to have good air circulation to be successful in growing healthy plants. Direct bright light is also not necessarily best for greenhouses. Diluting the light might also help to keep the seedlings from getting overly hot. Some opaque plastic sheeting might help.

Here's another suggestion. It sounds like you're having a difficult time keeping the seedlings moist given that you indicated that the soil is pretty dry at time of watering. One way to keep your seedlings moist (and to keep the humidity within the greenhouse at a nice high level) is to literally place the seedling pots in a tray of water. I've used old baking dishes that are about 2" deep and use pots that have holes in the bottom. The soil in the bottom of your planting pots will remain moist and will wick-up the water. This will promote good root development, which is key to growing nice healthy seedlings.

Good luck.

Nibsey

 

Thanks Nibsey.

The greenhouse is outside and does get a lot of sun (we get about 20 hours of daylight here at this time of year). I also have tomatoes in the greenhouse so I was trying to keep te temps as high as possible as I was under the impression that tomatoes preferred that. guess it is not compatible with leafy greens though (my lettuce is also limp and pathetic looking).

I have now opened all of the vents in my greenhouse (they were all closed before) in an attempt to cool it down during the day. The roof of my greenhouse is opaque and the side windows have some shielding due to external shrubbery so hopefully that plus the venting will moderate the internal temps.

Your suggestion about using a tray sounds good. But I've already transplanted the seedlings (maybe they are a little beyond seedlings) to the planters boxes in my greenhouse. I mentioned before that I was not sure if I was watering too much. This has been a problem for me in the past but I was using pots then. I think I have pretty good drainage in my new boxes so if there is little danger of overwatering (is there?!?!?) I could easily water more than I do right now.

 

There are many good greenhouse gardening books and references online, at the library, and in bookstores. June through September you will find that venting and a shade cloth are important, as temperatures can exceed 100 degrees.

 

Thanks Twelvepole. I guess my thinking was that this forum is a pretty decent online reference point.

I've taken the advice suggested, and now leave the vents open during the day (and occasionally at night) and some things have improved significantly. The basil and sage look great. the dill is as bad as ever but perhaps it has already passed the point of no return. the coriander got so bad I pulled it and replaced it with new, storebought seedlings.

My biggest concern now is one of my tomato plants. It should be thriving in the heat (or so I thought) but is just stumbling along. Oh well - I guess you can't win them all.

 

If you are gardening in a greenhouse, light, heat, moisture, and ventilation are the key issues. Once you get these issues under control, your green thumb will be all you need.