[Jamie Butterworth]

What in your opinion is the best flower to have growing on an allotment?

[DD.]

Cauliflower. 

[Jamie Butterworth]

Cauliflower. 

  I knew someone would put that

[mumofstig]

Cauliflower. 

but they ain't easy to grow , so I'd have to say English marigolds, or sweet peas near your climbing beans

[Swing Swang]

Nasturtium are pretty, act as ground cover and keep the weeds at bay, draw blackfly away from neighbouring plants, have edible flowers, and seed cases that can be pickled like capers.

[Swing Swang]

Comfrey flowers are pretty and purple (even sterile varieties)
Broad beans have the best smell.
Jerusalem artichokes left to flower are beautifully 'architectural' and are great for the insect and birds.
If you're saving your own seed then leeks look like alliums.

Basically you need to define 'best' before we can answer your question.

SS.

[Nige2Plots]

Sunflowers. You can eat the seeds and the Bees love them! They are a good looking flower too.

[MoreWhisky]

Sweetpea

[Hey Jude]

Just the one?...................got to be sweetpeas.

[Trillium]

If I had the space I'd place almost every flower I can think of.

But if you want the most effective flower, plant borage. The bees adore it and will come in numbers to also pollinate your veg crops. Borage is a small enough, but not too small, plant that won't get in the way or cause problems.

Bee balm will also encourage bees, but it's a tallish plant and spreads quickly.

[compostqueen]

Calendula, if I had to pick just one but I like Californian poppy Red Chief, Empress of India nasturtium.  I have a lovely sage variety on my plot which I grew from seed and it gets great looking pink changing to purpley blue flowers on it which last ages

I use annuals too mixed in the with veg, particularly Love in a Mist 'Jekyll Blue'  Oh and I couldn't do without cosmos and Sweet Williams 

[New shoot]

I get Borage growing on my plot every year but I've never planted it    It is pretty though so I don't mind.

My faves year on year are Calendula, Cosmos and Nasturtiums 

[Mazzie]

Lupins especially blue ones.  I love them as a flower but ive recently discovered they are great as a green manure so i intend to grow them as both this year

I also love sunflowers and wild poppys but just because they look lovely nothing to do with the lottie

[iggyboy60]

Definitely Sunflowers...my grandson loves them and when they start to tower over him he is forever jumping up and down to try and reach the highest point! Nigella is another and I would not be without my day lillies.