I know… I know… It’s not actually fall just yet. But as soon as the pumpkin spice Thomas’s English Muffins show up on the grocery store shelves (and I’m not making up that one!) its time to start talking about fall planting. But before we get to fall planting, let’s back up a bit to planting in general.
One of the most common questions I receive is about the best time to plant this plant or that. And I always start my answer with the following comment: plants are almost always happier with their roots in the ground than they are in a container above ground. While there are a few exceptions to this rule, such as plants that are severely maladapted to our soils, the vast majority of plants you’d want in your home landscape are much happier with their roots in terra firma.
Compared to the growing mix in a container, ground soil will generally remain cooler in the warm months, warmer during cold spells and doesn’t dry out as quickly as a container full of even the best quality growing substrate. That shrub or perennial sitting in a black plastic pot on the driveway in the blistering summer sun… it’s not going to be all that happy no matter how good you are at watering. Don’t believe me? Try sitting on that hot, sunny driveway yourself for a few hours…
So now on to fall planting…
Cooler days = better root growth
One of the major benefits of fall planting is the cooler temperatures compared to the midsummer months. Most parts of the US experience a nice, long fall season during which time the air temperatures gradually decrease and the soil temperatures moderate as well.
If you can remember back to July when we were flirting with the 100 degree mark on a daily basis, it’s no surprise that plants would struggle as much as the gardeners who tend them. During that time of year, root zone temperature is typically well above optimal (75-degrees F is best for root growth of most common landscape plants) and the high air temperature means the newly planted plant’s root system is put under tremendous demand to supply sufficient water to keep the top part of the plant happy. While plants planted in those hot conditions will generally be happier in the ground than they will be above ground in a container, it is still a stressful time. The cooler days of autumn are probably the best time for plants to re-establish new roots and acclimate to their new home.
Fall establishment means better roots for next summer
Fall is also a good time to plant because it will give newly planted specimens a chance to get their roots established in the ground before next summer. Next spring is a perfectly fine time to install new plantings but spring planted plants have to get their root systems established in a hurry, before the hot and dry summer weather moves in. If you can get them in the ground this fall, your new plants will get a jump on the next growing season and their established root systems will be much better positioned to get the plants through the stressful summer weather that we all know is coming.
Fall planting spreads the workload
Think back to last spring and the garden’s endless to-do lists you had to address. Start veggie seeds, buy annuals, mulch beds, fertilize the lawn, try to get the lawn mower started then give up and bring it to the repair shop that’s completely backed up with all your neighbors who also failed to get that work done in winter rather than waiting until April… You get the idea. If you can get it done now, why not check that one off your list rather than adding to next spring’s circus?
Of course, anytime you put a new plant in the ground, there’s the issue of irrigation. And planting in fall is no exception. Growing up in the Northeast I was accustomed to those September hurricane remnants that usually made their way up the east coast in September and October, dropping rain on our gardens. When I moved to Kentucky I was amazed to learn that on average, September and October are our two driest months of the year. And to compound the problem of limited rainfall, the gradually decreasing temperatures tend to make us gardeners think we might not have to water our new plants.
So how often do you water those new plantings? We’ll get to that in next week’s column but here’s a hint – more often than you think…
This article was originally submitted to the Courier Journal on August 29, 2022.