All can be planted now. For variety, plant mustard greens, parsley, spinach or the more challenging celery. Beets for greens or roots can be planted early but soak the seeds overnight to hasten germination. In our area, leaf lettuces are the most common salad greens grown. Countless varieties are available that can be harvested any time during growth up to maturity at about six weeks.
Plant rows of different varieties at intervals to ensure a continuous supply.
Spinach planted now as a border for the garden will mature before summer heat eliminates it. In late summer you can plant it again for a fall crop. Freshly harvested chives, leeks and green onions add zip to cooking. The race for the first vegetable to reach harvestable size is nearly always won by radishes. Try not only the familiar round red types but also the long white varieties.