Nature has a way of indicating time for certain tasks
Q. Is it true you should prune your roses when the forsythia blooms? Are there any other “signals” in nature to let us know the best time to do garden maintenance?
A. Most pruning of roses is done in the spring. The goal is to produce an open-centered plant to allow light and air to get in easily. The forsythia bush is one of the first shrubs to bloom and it signals the planting of early season flowers and vegetables in addition to pruning some plants.
This is an example of the concept called synchronous phenological indicator, or SPI. It is based on natural occurrences. It is used to understand when to control insect pests, plant seeds and perform garden maintenance. It goes back at least as far as when American Indians taught the North American settlers when to plant corn.
American Indians based corn planting on the size of an oak leaf. The oak is a late-emerging plant; their leaves need heat in order to grow. The amount of heat needed to emerge coincides with the soil temperature needed for good corn seed germination and growth. Some say, if the oak leaf isn't the size of a mouse's ear, the soil isn't warm enough to plant corn seeds.
Another well-known SPI is: It's time to look for morel mushrooms when the lilacs begin to bloom.
I prune my grapes in early spring and I use the holiday of Valentine's Day to help me to remember. Grapes are a deciduous shrub that's not known for its flowers. Prune other small and inconspicuous flowering shrubs and deciduous trees (those which lose their leaves) in the late winter or early spring before growth begins.
I also use fall holidays to maintain my dahlias. I cut at least half of each stem around Halloween. Then before the first frost, usually around Thanksgiving, I dig out the tubers to store until late spring.
It might be helpful to start a nature journal or write notes on a calendar to help keep track of when your plants begin to grow, when they bloom and when their leaves fall as the weather gets colder. This will help you to note when your garden maintenance needs to take place each year.
— Jennifer Richardson
Q. When is the best time to fertilize trees and shrubs?
A. Before considering fertilizing your trees and shrubs, get a soil test. A soil test will give you a detailed nutrient analysis and, ultimately, tell you if your plants would benefit from an application of fertilizer.
To promote adequate establishment of trees and shrubs, amend the soil at the time of planting. Recently planted trees and shrubs will benefit also from fertilizer applications two years after being planted. It is recommended to use a slow-release fertilizer spread evenly along the root-zone of young trees and shrubs.
Established, mature trees may benefit from an application of fertilizer to preserve foliage color, but it is not necessary. Keeping leaves that have fallen from shade trees along the root zone will provide mature trees with the nutrients needed for the following growing season.
It's best to fertilize in April right when leaves are starting to open, or before new growth is seen. Avoid fertilizing during extreme heat to prevent burning, or during wet, rainy weather to prevent runoff. Applications of fertilizer late in the season may cause new, young growth to not fully harden before cold, winter temperatures.
However, an application of fertilizer after the first hard freeze while soil temperatures are still warm will allow the plant to store energy for the following growing season, but the chance of fertilizer runoff will be increased.
Once again, not all trees and shrubs require fertilizer applications. If your plants are healthy and vigorous, adding fertilizer may cause unwanted burning and decreased root growth. Sometimes environmental factors that are commonly seen in our area, such as compacted soils and improper growing conditions (for example, lighting deficiencies, heat, wind or excessive water stress) may lead you to believe that an application of fertilizer may be needed. It is extremely important to get a soil test prior to fertilizer applications to make sure your tree or shrub isn't impacted by an environmental growth stressor.
— Jessica Stema
• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 on Wednesdays or email northcookmg@gmail.com. Visit web.extension.illinois.edu/mg.