Master Gardener Ann Bartlett discusses September tasks that pave the way for a healthy home landscape come spring.
As the long hot summer fades into fall, it is time to refresh the landscape and prepare your plants for a beautiful spring emergence.
Prune and Replace
Begin by cutting back spent foliage of perennials that are past their prime and removing those marked for replacement. Replace spent annuals with cool-season selections. Pansies are a great value and there are increasing options for ornamental kale and cabbages.
What Not to Prune
At this time of year perennials, shrubs, and trees store starch in their root systems before going dormant. In spring, they use this energy source to reproduce top growth and produce convert sunlight into sugar. Resist pruning subshrubs (small shrubs with woody bases) like lavender and rosemary until they begin growing again next spring. Pruning stimulates growth, which may not “harden off’ enough for them to survive frost.
Continue Weeding
Weed control is never off the agenda. This is a great time to spray herbicide on perennial weeds such as dandelions, because they take it into their roots and die. Apply a preemergent herbicide at the end of September to prevent cool-season weeds from sprouting. Try to remove annual weeds before they set seeds—which can endure in the soil for decades!
Amend the Soil
Renew the fertility of the soil by adding compost or shredded leaves. Check soil pH throughout the garden. Meters are readily available in garden centers. The pH can change over time as nutrients are leached from the soil or used up by plants, so it is a good practice to check it every two or three years. Most of our plants like a slightly acidic (6.1–6.5) situation. Chemicals to change soil pH take time to do their work, so this is a great time of year to apply them.
Renovate Your Lawn
Core aeration is a best practice, because it improves drainage and allows space for root growth. Overseed the lawn to thicken the turf. Apply fertilizer for a wonderful green-up come spring. And keep those weeds! University research has concluded that you can mow over autumn leaves. They decompose over winter, feeding the soil.
Divide and Plant
Divide spring and early summer blooming perennials such as iris and daylilies. The divisions need at least six weeks in their new home to become sufficiently established to survive through the winter.
Think about where to plant spring blooming bulbs. Tulips are best considered as annuals here, while daffodils come back year after year. Both require sun and good drainage. Daffodils can be planted under deciduous trees, but they need a few weeks of sunlight to nourish the bulbs after blooming. Let the foliage yellow for best re-bloom. Plant enough of them to make an impact.
Mulch Your Beds
Finally, refresh the mulch layer around plants. This provides insulation from vacillating temperatures, robs weeds of needed sunlight, and prevents bulbs from being heaved out of the soil. In addition, organic mulch decomposes, feeding the soil.
The shortening days of early autumn provide an opportunity to prepare the garden to re-emerge beautifully next spring.