Cover structures for dahlias

Hi Alan,covers there are many ways, poly tunnels are great but they really need to be big to be any good for dahlias. If you are growing in the typical row system 1m or 3 foot wide rows and 3 foot paths then growing four rows with three paths then that is approx 21 foot across by however long the rows are (my rows are 24foot long) I have two covers with four growing rows and another with three growing rows (growing 22-24 in double rows) this would be 18' across.
Then I also have a 54 foot poly tunnel that has three growing rows in it (192 plants in all)

For the structure I use 4" x 4" 6'6" posts tantalised timber, either concreted in place or use metal "feet" net posts the timber inserts into they are very good as the hold the timber securely at ground level. They will still rot eventually but treated they will last quite sometime. Now you need to erect centre posts 10' posts I try to go for 10 ' tall certainly no less than nine foot centre posts (head room is important as you need the air flow) as ther isn't enough fall remember the wider the covers the higher then centre post needs to be. So let's say you are growing in three rows I would insert my outside posts the put the centre posts in at 6' or 2 meters so 1m (path)1m (growing row) post 1m (path) 1m (growing row) 1m (path) 1m (growing row) so therefore 18' or 6m then timber for the rest is 2"x 3" tantalised timber. So therefore taking into account the fall from 10' to 6' you can measure then lengths before cutting. Note the centre posts will not be in the centre of the structure they are better to one side of a bed and path otherwise they get in the way. The structure will need firming up with cut off pieces of timber to add strength. If struggling have a look at the structure of a green house and use that as a construction aid.

The covering plastic want to be clear visqueen there are different kinds and available in different widths. I think the widths are 7.2 9.3 or can't remember the other width (look on LBS website they are as good as anyone) so for a structure 6m across the 7.2 is fine(I try to make the covers keeping in mind the width of visqueen available. Then you will order the visqueen to the length of the structure I would suggest 1/2 m to 1m over hang on each end. The plastic is then help in place with slate batons and screws pulling the visqueen tight as the slate batons are secured.

Hope this helps and you can understand some of it, if not pm and I will try to help more

Hi they are not as good as the polytunnel but as long as you roll back the covers after the show season and before the winds then you are ok I roll the cover back and hold them in place with long cable ties usually ok for several years.



I agree poly tunnels are good but to grow any number you do need to get a large tunnel, not all varieties are suited to tunnels. But yes tunnels are good I have gutters down the sides of mine and you should see how fost the water tubs fill up.

How tall? on average 3' - 6' but grown in big greenhouses they can get over 12-14 foot tall the same varieties, under normal covers and in polytunnels average height uncovered they will not grow quite as high. Different varieties grow at different heights.

Polytunnels not Permitted ?

Blasphemy !!!

I think it's because the powers that be decided they are not 'athletically pleasing' to the eye!..no problem with greenhouses or large wooden structures..