Posted: 24/04/2017 at 19:39
Strawberries are hardy, mine are outside in everything the weather throws at them all year round. They'll survive anything! I don't grow onions but I wouldn't have thought they'll be a problem. Blossom on young fruit trees can be protected with a cover of any kind that's suitable, if you're really worried, but my apple trees are fine and we've already had at least two frosts in the last week.
Raspberries etc are hardy, so I'd reckon you only need to bother with the seedlings - put them somewhere sheltered - against a house wall for instance. If you don't have fleece - use bubble wrap or an old blanket or similar. Even the shelter of other shrubs or a garden table/bench will do.
Plants that are grown a bit 'harder' willl withstand fluctuating temps and conditions far better than those which are too cossetted.