rasied beds-greenhouse cover

(Question)

1. I have new raised beds in my vegetable garden and also included insertions for pvc pipes to make a mini-greenhouse/cold frame. Over the top I have put some plastic and attached at the sides with groppets. I did not specifically put any slits for ventilation in the top, since the sides are not in away sealed just held in place. See attached picture.

I noticed on the first sunny day last week that a lot of moisture had accumulated inside and that the plastic was sort of fogged over. I wonder if this is a problem?

I plan to put in lettuce seeds and other early seeds in the next week or so but it worries me that too much moisture might rot them. Or that air circulation will not be adequate. Any advice?

2. I also wonder with raised beds how you advise amending the soil from year to year?

3. With raised beds, can one plant same thing in same place over many years or is it better to rotate?

Thanks.

 

(Answer)

Dear gardener, how exciting to have raised beds for your veggies!

Although the picture did not attach to the system, it seems by your description that it was well built. In terms of  your questions, I will try to address them:

1-     Excessive moisture can be a bit of a problem if air circulation is inappropriate as it creates a very good environment for fungi to grow. Vegetables need to be watered but excessive air moisture can be damaging. Also keep in mind that, in sunny warm days, the cold frame can actually become too hot for your seedlings.

2-     Soil will be slowly depleted as the vegetables use  it to grow and as compaction occurs naturally. Adding composted manure annually will help re-nourishing the beds.  If the bed is still quite high in soil, you can remove the top 10-15 cm of soil and replace it with new one.

3-     Plant rotation in vegetables is needed regardless of planting location. Rotation is done for few reasons:

  1. To ensure the soil is not depleted of essential nutrients from some heavy  feeders (tomatoes for instance).
  2. To avoid diseases than linger and attach certain families (potatoes and tomatoes, for instance)

Please refer to the Toronto Master gardeners’ gardening tips for useful information on growing cold crops: https://www.torontomastergardeners.ca/index.php/category/gardening-tips/

Good luck with your new vegetable beds and hope this information helps.