Nearly all our spring blooming plants have finished now and are in the process of putting their energy into storage if a bulb. Next year's flowers depend on the plants ability to continue to produce food reserves until they naturally die down. The very early spring bulbs have already disappeared from the beds in fact. Bleeding hearts are also beginning to go away too. Currently daffodils are showing signs of slowing down with yellowing leaves. That will continue until all the foliage has yellowed and dried down. That will be the safest time to clean up, knowing that those bulbs will be back in all their glory in 2017. Tulip bulbs have also likely died down by now as well. If you need to divide or move bulbs in late summer or early fall, be sure to mark their location so you can find them without slicing the bulbs accidently with your garden trowel or shovel.
When it comes to shrubs and ornamental flowering trees, they store and prepare for next year differently. Shrubs that bloom early in the spring will be setting up those flower buds shortly and readily seen by this fall on Viburnums and Lilacs. This is why we prune just after they bloom. Pruning late summer removes the bloom show for 2017. Some shrubs like tree lilac and dentatum viburnum (an expectation in the viburnum group) and spirea flower on current growth with energy produced since spring. If pruned in the late fall or early spring, flowers still show up.
Fruit trees are a group of plants that divide up food reserves between what has to happen yet this summer and the spring of 2017. Energy being produced right now is used to fill out the fruit. Too many fruits and the fruit tree will not have enough energy to create flower buds for 2017. Gardeners may know the expression "alternate year bearing" as a description of what happens to the fruit tree. Heavy fruiting in one year will limit flowers for the next. The following year without flowers and fruits the tree generates lots of annual growth and fruit buds. The cycle repeats itself until we intervene by thinning the fruits in a heavy bearing year to ensure enough food to create flower buds annually which will also slow the vegetative growth, keeping the fruit tree smaller.
Lawn grasses go through transition as well. Energy in the spring is directed into the grass blades as a part of the natural spring flush gardeners have come to expect. As our summer heats up and dries out, energy is used to maintain growth until the grass plant naturally goes dormant. In the late summer and early fall when growth resumes, energy is directed into the grass plant root system for the winter and generating roots that create new shoots to thicken up the lawn. If is the reason it is often suggested that if fertilizing only once a year, the better time is the fall.
Get into a daily routine of walking your yard and observing these transitions. It will help you understand why your plants grow, flower, set seed, produce a pod or nut the way they do.
About the author: Richard Hentschel’s expertise extends across several subject areas with specialties in lawn care, fruit tree production, woody ornamentals, and home and community gardening. During his 45-year career in horticulture and agriculture, Hentschel became a well-known and respected expert for commercial and homeowner audiences, industry organizations, and media. He retired from University of Illinois Extension in April 2022 with nearly 30 years of service as a Horticulture Specialist and Educator in northern Illinois.