We are setting up 8 acres certified organic. We also have a food caravan / commercial kitchen where we make jams, baked goods, canned vegetables and soups etc. that we are marketing on consignment in a craft market in Wellington (New Zealand capital).
We think a good economic base for this will be able to get a few dozen families who we supply a weekly box of vegetables and seasonal fruit (as well as cold storage apples/pears/ kiwifruit/ oranges that we buy by the box).
What keeps scaring me about this, is the thought of growing rows and rows of broccoli, and getting them to head that the correct time. We also have a number of cattle, sheep goats and chickens. So I don't think any will be wasted if they go to seed, but it would be good to keep up a constant supply to customers. In the middle of winter we have average minimums of 5C and average maximums of 11C, and as we are 8km from the beach, or frosts have never got past -4C.
We also have a 300 square metre / 300 square foot green house that we will put up, so that we can grow warm weather crops out of season, and also hopefully have herbs and celery inside that seeds at a different time to the outside planting. (? and maybe carrots?)
We will store pumpkins, potatoes and onions, and again, may be able to buy certified organic produce by the sack to supplement our own supply.
Anyone got any experience and advice on how easy it is to maintain a constant supply year round?
If you grow a raab (also known in Italian as rapini) type of broccoli, you will have less of a problem, since it is continually producing smaller florets. This requires a bit of customer education on your part, to entice your customer away from the big heading varieties of broccoli (that are good for one, or maybe two cuttings, and then are worthless) to the other varieties. This is possible, because these less marketed broccolis can be more flavorful than the ordinary variety.
Heading broccolis and cauliflowers belong in the same category as determinate tomatoes: crops engineered to be grown and processed on a production line, with as few field passes of the machinery as necessary. That's neither permaculture nor good tasting. But it is what big agriculture has conditioned the public to accept.
It sounds like you are trying to embrace the CSA model. I have worked for several farms with CSAs and none of them (nor any I am aware of) offered produce to their subscribers year round, but rather for 8 to 9 months of the year with the last box being a big send off full of storage crops.
That being said Several of the farms I worked for where also direct wholesalers to co-ops and grocers and the like - and we did sell to them year round. During the depths of winter we would rely on selling from our stores from our fall harvest like beets, potatoes, and winter squash as well as leeks and parsnips and the like.
Either way there is a learning curve and there is an unavoidable margin for error. The key is to keep commitments loose and work with customers who are cool with that. Especially when starting out over plant and plant lots of stuff knowing that some will fail and some will get away from you. Make it clear to the customer that you are committed to supplying them with produce, that they will get SOMETHING but also ask them to be realistic and tell them what (and when) you expect to be harvesting. A newsletter that leads the weekly box by 2 to 4 weeks is a huge boon for the customer and a giant pain in the ass for the farmer.
Bolting plants can be tricky. You can't count on planting in succession. Even if you plant out one row one week, and one the next, and another the next a good hot/dry spell will likely leave you harvesting them all over the course of 4 or 5 days. But not always. It's tricky. Again I will stress having a variety and a number of 'fall back' 'crowd pleasing' fillers. In my experience this is generally more salad mix.
You can get hella sneaky with greenhouses. I could regale you with stories about the 9$ bunch of organic carrots which flew off our market tables, but I won't.
The key is to learn your plants. Get a feel for your climate. Then its mostly timing timing timing timing timing timing timing timing timing timing timing timing timing
and what is it they say?
Nothing ventured nothing gained
Best of luck, hope this is useful. I imagine NZ to be pretty similar to the PNW, but have never gotten to visit way down there.