Can I transplant my spent spring flowers like daffodils now(in the spr

yes but you will not get blooms till next season

Yes ,when transplanting make sure you leave the foliage on as the bulbs feed off of it.

Best to lift now with the leaves on, leave to,dry out and replant in the autumn

Wait until greens die back on their own. They are feeding the bulb so it can bloom again. Even if you are careful to move bulb and greens you may miss smaller bulbs that are living off of that one. The roots are forming new plant bulbs.

Yes, best to wait until the leaves die back; the leaves are adding to the growth of the bulbs for next Spring. Once the leaves have died, remove the bulbs, shake the soil from them only if you are going to let them dry before replanting in the Fall; other wise re-plant into their new location right away. IF you decide to dry them & wait until re-planting in the Fall; make sure you store them where squirrels & such won't eat the bulbs in the meanwhile.