When people think about planting flowers and garden beds, spring usually gets all the attention. But if you’re planning to add more perennials to your landscape, early fall is actually the ideal season to get them in the ground.  

Our climate here in the Treasure Valley offers the perfect fall window to establish perennials successfully before winter. With the right timing and a little preparation, you can give your garden a head start that pays off for years to come.  

A Quick Note on Perennials 

If you’re newer to gardening or just exploring your options, it’s helpful to understand what makes perennials worth planting – especially in the fall.  

Perennials are plants that return year after year, growing back from their roots each spring. Unlike annuals, which need to be replanted every season, perennials settle in for the long haul. Once established, they typically require less water, less maintenance, and less money over time.  

Many also become stronger with age, blooming more abundantly as the years go on. Plus, you can divide mature perennials every few seasons to create new plants or collect seeds from certain varieties to grow even more plants for little cost or to share with friends and neighbors. 

So, when you plant perennials in the fall, you’re not just filling your garden for one season – you’re laying the groundwork for a landscape that builds on itself year after year, with less effort and more reward. 

Why Plant Perennials in the Fall? 

Fall planting gives perennials a solid head start. Here’s why the season works so well” 

Warm Soil, Cool Air 

As summer heat fades, the soil remains warm, even as daytime temperatures become cooler and more pleasant for working outdoors. This combination encourages strong root development without pushing top growth, which is exactly what you want before winter. 

Reduced Stress on Plants 

Cooler air temperatures mean less transpiration (water loss), so newly planted perennials are less likely to dry out or go into shock. You’ll spend less time watering, and the plants won’t struggle with the intense heat that often follows spring planting. 

Natural Moisture and Rainfall 

While our region doesn’t get as much rain as other parts of the country, fall generally brings more consistent moisture, reducing the need to irrigate as frequently. This helps ease your plants into dormancy without stress. 

Fewer Pests and Diseases 

Insects and fungal diseases that thrive in summer heat tend to wind down in the fall. That means fewer threats to young perennials as they’re trying to establish roots. 

Earlier Spring Growth 

Perennials planted in the fall wake up early in the spring. Their roots are already in place, so they begin growing as soon as the ground warms. That means earlier blooms, stronger plants, and less effort from you come springtime. 

Timing Your Fall Planting 

You want to give your new perennials about 6 weeks to establish roots before the first hard frost. 

In our area, the average first frost date is usually around mid to late October. So the sweet spot for planting is typically early to mid-September – although planting can continue into early October is the weather stays mild. 

USDA Zone Info: This region falls in USDA Hardiness Zoned 6b-7a (depending on your location), with average minimum winter temperatures ranging from -5°F to 5°F. When choosing perennials, make sure they’re rated hardy to at least Zone 6. 

How to Plant Perennials in the Fall (Step-by-Step) 

Getting your perennials off to a strong start in the fall doesn’t require much – just a few simple steps done right: 

1. Choose the right plants 

Select perennials that are hardy to at least Zone 6. Look for varieties suited to your garden’s sunlight, soil type, and moisture levels. Native and drought-tolerant plants tend to be excellent for long-term success. 

2. Dig the hole 

Dig a hole as deep as the root ball and about twice as wide. Loosen the bottom of the hole slightly so roots can begin penetrating the native soil. Avoid digging too deep – settling over time can cause the crown of the plant to sit too low, leading to rot. 

3. Prep the roots 

Before placing the plant in the ground, take a moment to inspect the root ball. Gently loosen the roots around the outside with your hands. If roots are tightly circling the inside of the post, use a garden or hori-hori to score or rough up the sides of the root ball in a few vertical cuts. This helps prevent the roots from continuing to spiral and instead encourages them to grow outward into the surrounding soil – which is key for proper establishment. 

4. Backfill with native soil 

Refill the hole using only the soil you dug out – don’t add compost or other amendments to the planting hole. This prevents drainage issues and encourages roots to spread beyond the planting hole into the surrounding soil. 

5. Water thoroughly 

Water deeply right after planting to settle the soil and eliminate air pockets. Continue watering every few days if rain is scarce, especially during warm fall spells, until the ground begins to freeze. 

6. Top-dress with compost and mulch 

Once planted, apply a thin layer of compost on the surface (about ½ inch) to gently enrich the soil slowly over time. Then add 2-3 inches of mulch to insulate the roots and conserve moisture – but be sure to keep mulch a couple of inches away from the crown of the plant to avoid rot. 

7. Skip the fertilizer 

Hold off on fertilizing in the fall. You want your new perennials focused on root development, not top growth, which could be damaged by frost. 

Bonus: Consider Dividing Established Perennials 

If you have mature perennials already growing in your yard, fall is also a great time to divide and transplant them. This helps rejuvenate the original plant while giving you more to spread around your landscape (or share with neighbors). 

A Long-Term Investment in Your Landscape 

Fall planting takes some planning and a little effort, but the payoff is big. By getting your perennials in the ground now, you’re creating a stronger, more resilient garden that will reward you with earlier growth, longer blooming, and better drought tolerance – all while cutting back on the work you’ll need to do next spring. 

So, if you’ve been thinking about refreshing your garden beds or expanding your pollinator friendly plantings, now is the time to dig in.