Green Day might’ve been happy to sleep through the ninth month, but you shouldn’t – especially as there are two jobs to do in the garden before September ends. Yes, we know; the air is cooler, the evenings are drawing in, and many summer plants are starting to fade. It feels a lot like the gardening season is over, but in truth, this is a pivotal month for setting up success next year.
Whether you’re ticking off essential September lawn care tasks, figuring out which shrubs to propagate, or simply planting flower seeds, there are likely more than a few things on your gardening to-do list already. If you are running short on time, though, don’t despair; doing just two jobs right now will see you rewarded with spring color and healthy perennials.
Rush into the wrong task, though? Well, you may wind up doing more harm to your garden than good…
Before the first frosts arrive, it’s important to set aside some time in your week to finish off two essential jobs in the garden. And, while it may be tempting to continue this same energy (particularly if you're worried about missing the things most gardeners forget in September), there’s one task best left until spring.
Let's dive into it, shall we?
Do Now: Plant Spring-Flowering Bulbs
In the bleak midwinter, there’s nothing that lifts the spirits quite so well as the sight of those first daffodils and crocuses pushing through the cold soil. That’s why planting spring-flowering bulbs in September is one of those essential jobs to do in the garden before the month ends and the ground freezes, especially if you’re in one of USDA Hardiness Zones 3-8, where cold winters are the norm.
Daffodils, crocuses, early tulips, snowdrops, and hyacinths are all perfect for this, as they need several weeks of cool soil to develop roots before the real freeze arrives. Plant too late and they may not establish, leaving you with patchy spring displays.
You can either plant en masse, or mix and match for a more naturalised look across borders and under deciduous trees. Choose a well-drained spot (bulbs rot in soggy soil), plant two to three times as deep as the bulb’s own height, and be sure to water them in before mulching.
Adding a couple of teaspoons of bulb fertilizer, such as Espoma Organic Bulb-Tone, available from Amazon, to the planting hole will set bulbs up for the best possible start come spring.
Do Now: Divide Perennials
By late summer, many perennial plants (like hostas, coneflowers, black-eyed Susans, daylilies, ornamental grasses, and asters) will have grown into great big crowded clumps. Left alone, these plants will exhaust the soil, not to mention produce fewer flowers and bare middles. Take care, then, to add dividing perennials in September to your list of jobs to do in the garden before the month ends.
Yes, dividing perennials in the fall – particularly in USDA Zones 4-9, where the soil is still workable but the heat has passed – is a great way to give these comeback kids a health reset, not to mention score yourself some free plants for next year.
It’s a simple enough job; use a garden fork or spade to lift the clump carefully, shake the soil to expose the roots, and cut the clump into smaller sections (we recommend using The Original Hori Hori Namibagata Japanese Stainless Steel Weeding Knife from Amazon to help with this, although many pros use a humble bread knife!). Each should have healthy roots and a few shoots. Then, replant them, taking care to water them in well and mulch them, too.
Warning: avoid dividing any plants that bloom in fall, such as mums or sedum; they should be given the chance to finish their show first!
Leave Until Spring: Pruning Woody Shrubs
It’s tempting, when the garden looks messy, to reach for the pruners. Resist! A heavy pruning of shrubs like roses, hydrangeas, lilacs, and viburnums absolutely doesn’t belong on your list of jobs to do in the garden before September ends; leave it until springtime.
Why? Well, because cutting back in fall often encourages new tender growth just as the frosts arrive, leaving them vulnerable to damage. You also risk removing any flower buds that form on old wood, making for fewer blooms next year. And don’t even get us started on the fact that all of those old stems are vital for beneficial insects and foraging birds.
If you really can’t resist a quick prune, focus your attention on tidying away any dead or diseased wood. And take a gander at the plants to prune in September, too; there's sure to be something you can do!
Essentially, gardening in September is all about balance; think preparing for the year ahead, without overtidying and making any garden cleanup mistakes. Plant bulbs for spring joy, then, and divide perennials to keep them healthy – but don’t prune any shrubs yet, no matter how tempting it may be.
By doing so, we promise that you’ll step into next year’s garden with color, vigor, and far less hard work ahead of you. Happy gardening!
