Hawthorn is in full bloom over here in its natural habitat. Have these been artificially retarded in cold storage that they are still dormant? If so I'd plant them ASAP in their final positions, water well and cross my fingers.

You say you have a 'small' yard. Hawthorn is mainly used for field boundaries here rather than in gardens. It's not a small subject and needs regular cutting to maintain as a hedge. It's also very thorny.

how large are they.. is this a quality provided???

if smallish.. i would probably pot them .. couple to a pot.. and grow some roots.. and then plant them in fall ...

our weather is similar.. and had you planted them last week.. with the near hundred degrees we had this weekend.. they would have been in trouble.. imo ...

the fact that your seller couldnt send them on time.. makes me wonder if it is arbor day??

ken

OP says they're whips so presumably just unbranched sticks. I'd skip fiddling with pots and just get them in the ground. These things are tough as old boots. As long as they're watered, and perhaps shaded, if they have new leaves, they'll be fine, I'm sure.

If these are true Crataegus monogyna and not the C. x media of which much planted garden forms such as 'Coccinea Plena' (sold incorrectly as 'Paul's Scarlet') consist then this species is a significant weed in the northern US. And should therefore not be planted intentionally, despite its admitted beauty when in flower!

I did not know they were a weed in NA. They're an integral feature of the countryside here. Mile upon mile of hedging. Aka May trees,

This is all very helpful. Thank you for your comments.