Wait to remove the foliage on your tulips, daffodils, hyacinths, and spring-flowering bulbs until it’s gone hyacinths, and spring-flowering bulbs until it’s gone fully  yellow and pulls easily out of the ground. If there’s still some resistance when you try to pull it out of your  garden, the bulbs are still absorbing sunlight for next year’s floral display. It’s a good time to map out your bulb garden if you haven’t already. Refer back to your diagram this autumn when you plant more spring-flowering bulbs — that way  you know exactly where your existing bulbs are and which varieties are where. Taking a photo of your garden  is an easy way to remember.

Replace your cool-season annuals (such as pansies,  nemesia, and diascia) as they fade with the onset of hot,  dry weather. Plant heat-loving annuals (such as  angelonia, petunias, or salvia) in their place to keep  your beds, borders, and containers looking great
through fall.

Walk through your yard at least once a week and cut off  dead, faded flowers. This process is called deadheading  and it encourages many varieties to keep blooming.
Deadheading prevents your plants from going to seed  (so you won’t have a crop of seedlings to pull) and can  protect your plants from some fungal diseases.

If certain varieties frequently suffer from the same  diseases, divide or prune them so air can flow freely  between the branches and leaves. Many fungal diseases  love still air.

Encourage critters such as snakes and toads as both eat slugs.  Prune lilacs and other spring-flowering shrubs once  they’ve finished flowering. If you prune them after this
month, you could be cutting off next year’s flowers.

Make more of many of your favorite shrubs! It’s an ideal time to take cuttings of trees and shrubs, such as  chokeberry, butterfly bush, spiraea, serviceberry,  hydrangea, dogwood, and magnolia.
Selections from: http://www.bhg.com/gardening/gardening-byregion/
northeast/june-tips-the-northeast/