How Late Can You Plant Perennials? A Complete Guide

As an avid gardener, I’m always looking for ways to extend the growing season and plant as late into fall as possible. Perennials are a great option for fall planting, as many varieties do well when put in the ground in autumn In this article, we’ll explore how late you can plant perennials based on your hardiness zone, the best perennials for late season planting, and tips for success.

When is the Last Chance to Plant Perennials?

When you can plant perennials in the fall depends on what USDA plant hardiness zone you live in. Here are some general guidelines .

• Zones 3-4: Finish planting marginal perennials by early October. Plant cold-hardy natives until late October. End all planting by early November before ground freezes.

• Zones 5-6: Stop planting tender perennials by late October. Plant hardy varieties until mid November. Halt all planting by late November to avoid frost damage.

• Zones 7-8: Plant tender perennials by late November. Hardy perennials can go in the ground through December. End plantings by mid December before chill sets in.

These are just general rules of thumb – also consider your specific climate and weather patterns. Track soil temperatures in your garden to see when the ground starts cooling off. Water new plantings diligently until the ground freezes. And prevent frost heaving in winter with mulch.

The Best Perennials for Late Season Planting

You can plant most perennials in the fall, but there are some that do better than others. Pay attention to these top types.

• Cool season bloomers – Crocus, hellebores, iris, forget-me-nots, and pansies thrive when planted in fall. Winter chill actually initiates their flower development.

• Native wildflowers – Black eyed Susans, coneflowers, asters, and goldenrod establish quickly when planted in fall since they are adapted to Midwest winters.

• Ornamental grasses – Switch grass, maiden grass and fountain grass spread vigorously when planted in autumn and stand up well to winter snow.

• Sedums – Meaty sedum varieties like Autumn Joy and Matrona store water in their leaves and can be planted up until early winter.

You can plant perennials well into late fall as long as you choose hardy varieties that will do well in your area.

How to Plant Perennials in Autumn

Follow these tips when planting perennials in the fall season:

• Water thoroughly at planting time and continue watering until ground freezes.

• Prepare soil well with compost to encourage root establishment.

• Plant at proper depth, being careful not to bury crowns too deep.

• Apply 2-3 inches of mulch like wood chips or straw to prevent frost heaving.

• Stake tall perennials that could flop over from heavy snow.

Follow these basic steps when putting perennials into the ground in fall:

1. Choose a spot with decent drainage and ample sunlight. Amend soil if needed.

2. Dig a hole twice as wide as the root ball but no deeper than its nursery pot depth.

3. Place the plant in the hole with its root ball level with the ground.

4. Backfill with native soil, tamping lightly to remove air pockets.

5. Water thoroughly until the soil is saturated.

6. Mulch 2-3 inches around the plant, leaving the crown clear.

7. Keep watering 1-2 times per week until the ground freezes solid.

Properly preparing the planting area, caring for perennials at planting time, and providing attentive aftercare will set them up for success.

Dividing & Transplanting Perennials in Fall

In addition to putting new perennials in the ground, fall is also an ideal time for dividing and transplanting ones you already have:

• Divide spring & summer bloomers in early fall to allow plants like hostas, astilbe and bee balm time to reestablish roots before winter dormancy.

• Divide fall bloomers in spring to avoid interrupting mums, sedums and asters that set next year’s flower buds in autumn.

• Transplant overgrown perennials by lifting and replanting the healthiest sections of overcrowded plants.

Use the same planting guidelines outlined above when dividing or moving existing perennials in fall. Water consistently, apply mulch, and give them 4-6 weeks minimum to recover before cold weather arrives.

Overwintering Tender Perennials

While hardy perennials are fine for fall planting, tender varieties like hibiscus and mandevilla need overwintering protection in zones 5 and below. Follow these tips to overwinter them:

• Bring pots inside before temps drop below 50 degrees F to a sunny spot.

• Trim plants back by one-third to one-half to reduce stress.

• Stop fertilizing by September so plants harden off.

• Water minimally just to keep soil slightly moist.

• Move pots periodically to evenly distribute light.

• Keep humidity up by misting and using a humidifier.

With a little care indoors over winter, many tender perennials will survive dormant in pots. Just transition them gradually in spring and fall.

The Benefits of Fall Planting

There are many advantages to putting perennials in the ground in autumn:

• Soil is still warm, encouraging root establishment before frost.

• Cooler temperatures prevent moisture loss and transplant shock.

• Ample fall rain provides the steady moisture vital for new plantings.

• Weed pressure subsides as cooler weather halts weed seed germination.

• New roots have ample time to develop before winter dormancy.

• Nurseries offer end of season discounts on surplus inventory.

By properly timing perennial planting in fall for your zone, you can extend the growing season and prep your garden for next spring. Add new plants, divide existing ones, and fill in empty spaces opened up from summer fade. With the right selection and care, fall planting can boost next year’s garden performance.

Bottom Line

It’s perfectly feasible to plant perennials deep into fall provided you choose suitable plants and give them proper care. Focus on hardy varieties adapted to your climate. Plant them at the right time for your zone and tend to them diligently through fall. With smart preparation, most perennials will flourish when planted in autumn and give you a head start on next year’s garden.