Perennials that require no fertilizer: Included are ornamental grasses, false indigo, ground covers, butterfly weed, bee balm, coneflowers, black-eyed Susans, sea holly, dianthus, asters and veronica.
No matter the plants you are trying to feed, scheduling the correct timing is important. Applying fertilizer in the wrong season can cause increased tender new growth that can be damaged, especially if applied in cold weather in late fall or in winter. So it is best to stop fertilizing during dormant seasons.
Perennials that do best with no supplement fertilizer include butterfly weed (Asclepias tuberosa), false indigo (Baptisia australis), asters, pinks (Dianthus spp.), rock roses (Helianthemum spp.), sea holly (Eryngium spp.), bee balm (Monarda didyma), speedwell (Veronica spp.), coneflowers (Echinacea spp.
Some annuals such as morning glory and moon flowers don't like fertilizer as it promotes more green foliage and fewer flowers.
Perennial flowers are a bit different than annuals. They generally require less fertilization and since they often slow down growth in autumn to prepare for dormancy, fertilization should be avoided after late summer.
Fertilize your plants, shrubs, trees and lawn to stimulate root growth, which will help your plants survive the winter and recover earlier in the springs. Fertilize perennials in the early fall for extended life. Fertilize trees and shrubs in the late fall to give them a boost before the winter.
During fall, September is the best time to fertilize your lawn. Grass is recovering from a long hot summer and may be coming out of a drought-induced dormancy, so you'll want to give your lawn a shot of nitrogen to push blade growth.
Beginning late summer and through September and into early October is a great time to fertilize many plants. This includes lawns, young trees, shrubs that need to grow more leaves and groundcovers that need to spread and cover.
August is an ideal time for gardeners to give their plants a boost into the later stages of growth. Many people who are just learning how to garden at home overlook the benefits of fertilizing their plants.
Timing: Apply summer lawn fertilizer once between June and August, 6 to 8 weeks after the late spring feeding.
Water and Feed Your Perennials
You can easily water and feed at the same time with Miracle-Gro® Liquafeed®. When watering, avoid perennials' leaves to prevent disease, and aim for a soil consistency that is neither too wet nor too dry.
Broadcasting a slow release fertilizer is the best choice to meet season-long plant nutrient requirements, but you can also use a balanced fertilizer such as 20-5-10. If your soil test indicates that you do not need phosphorous, choose a product such as 20-0-10.
Standard Miracle-Gro “all purpose plant food” fertilizers are synthetic and should not be used in organic gardens.
Avoid applying fertilizers when plants are dormant or under heat and drought stress. Fertilizers should be incorporated into the soil to prevent losses. If you cannot physically incorporate a fertilizer at this point in the season, it may be best to stick with a water-soluble fertilizer.
Don't fertilize plants or trees during hot summer months
An increase in growth means an increase in water and nutrient needs. During hot spells, it is especially hard to keep up with plant water and nutrient needs as soils dry out quickly and water may not be readily available.
No matter which fall gardening project you choose, be sure to make plant roots super-happy by using Miracle-Gro® Potting Mix (for containers) or Miracle-Gro® Garden Soil for Vegetables & Herbs (for in-ground).
Applying either fertilizer or weed killer when it's hot out can damage your lawn. You're better off waiting until later in summer to fertilize. Extension offers a handy calendar for when to do what to your lawn here: extension.umn.edu/planting-and-growing-guides/lawn-care-calendar .
Apply Fertilizer
Warm season grasses, like Bermudagrass, St. Augustine grass, Centipede grass, Zoysia grass, Bahia grass and Carpet grass, should be fertilized in the late summer. Cool season grasses, like bent grass, Kentucky bluegrass, fescue and ryegrass should be fertilized in the fall.
The exact timing for when you should fertilize your lawn in the fall varies based on weather conditions and climate zone. In most regions, October is not too late for fall fertilizer, and you can even put fall fertilizer down in November in many places.
Fall Fertilizer Timing
For the majority of cool-season lawn owners, apply fertilizer anywhere from September through early November.
Choosing a lawn fertilizer blend
A complete fertilizer with a high ratio of both nitrogen (N) and potassium (K) is essential for root growth, winter hardiness and disease resistance. An ideal fall fertilizer blend will have a nitrogen to phosphorous to potassium (N:P:K) ratio of 24-4-12.
The November fertilizer application is the second most important time for cultivating a cool season bluegrass or tall fescue lawn, with September being the most important application. The November application helps the lawn flourish in several ways.
Watering after fertilizing washes the fertilizer off of the grass blades and into the soil, where it can get to work nourishing your lawn. It's also important because if fertilizer sits too long without being watered in, it can burn the grass.
We recommend waiting 24 hours after fertilizing to water your lawn, which will give the fertilizer time to settle. After the 24 hours are up, it's important to give it a good soak—not just a quick spritz with your hose—to activate the fertilizer and help the critical nutrients absorb into the soil.