By now, dormant oil spray for trees and shrubs to prevent disease and insect problems, is no longer an option. Most deciduous plants have leafed out and/or budded, and no chemical applications can be applied until flowers pass. After flowering, all-season oil (or Neem), and copper based fungicides will be the best remedy for disease and insect problems.
Corn gluten is a great pre-emergent weed control and fertilizer in one organic process. However, the time for corn gluten application has passed (it was recommended that it be applied by April 25). Be cautious: if weed seeds have already germinated and taken root, a late application of corn gluten will only serve as fertilizer for the weeds. No grass seed should be attempted for 4-6 weeks after application. If weeds are not a problem, overseed thin or bare areas and use organic or starter fertilizer to provide a dense stand of thick turf that will crowd out weeds. Usually 2 seedings are necessary.
Peas can be planted now - about 1 inch deep and 2-3 inches apart. Use organic fertilizer in the trench and every 2-3 weeks along the sides of the rows. No inoculants are usually necessary. Leafy green veggies like arugula, kale, lettuce, spinach, broccoli, cauliflower and all brassica cole crops can be planted with organic fertilizer mixed with the soil in the hole. Apply granular fertilizer every 2-3 weeks. Between applications of the granular fertilizer, use water-soluble organic fertilizer every time you water. Do not attempt to plant tender crops until the end of May. Mean temperatures must be constantly above 50 degrees.
When making any new transplants, be sure to use a root stimulator like Biophos or Nutriroot. These products have replaced excessive phosphate-based root nutrients, and allow for the Mycorrhizal (beneficial root synergy bacteria) action of root stimulants to accelerate root growth.