Gardening Green with Doug 

Cooler Temperatures Signal Start of “Third Season” Plantings

By Doug Oster


August 18, 2021

Sitting quietly, alone at night, I opened all of the windows in a room listening to a gentle rain persist for hours. The humidity was still stifling, but after a long hot, dry spell, the sound of the rain was such a relief.

It signaled the start of what I call the “third season.” This is the beginning of fall planting, which is almost as critical to the garden as the first plantings of spring. Cooler temperatures, shorter days and moist soil provide the perfect conditions to get back into the garden.

Vegetable Planting

This is the right time to plant more seeds of leafy crops like lettuce, arugula, kale, cilantro and spinach. For years, late-planted spinach has outperformed the early sowing in April, sometimes even overwintering to be harvested again as the snow melts.

Swiss chard is one of the easiest plants to grow. It’s a spinach substitute with thick stems, which should be started from seed now. (See the free Swiss chard seed offer below)

There are unusual greens, which will take a foothold now and thrive as the cool weather arrives. Tatsoi, corn mache, ‘Seven Top’ turnip greens can be sowed right now for fall harvest. The tatsoi is from the kale family, it has deep green rosettes and a mild flavor. If the kids don’t like kale, throw tatsoi in the salad, they’ll love it. You’ll be able to find the seeds locally.

Radishes and beets are two root crops that can be planted now. There’s plenty of time for the radish to reach fruition, and the beets will be ready before the first real snow. Beets can also be covered with a thick layer of mulch and harvested during a winter thaw.

Vegetable plants will be appearing soon in garden centers, those can help supplement what’s been started by seed. They also can fill holes from vegetables that have run their course.

Perennial Planting

Every nursery I’ve stopped at has perennials on sale. (That is, plants that return annually and often times increase in size through the years.) Nurseries are selling the plants that have been in stock all summer. One reason to shop at your local nursery is that you know those plants have been cared for properly all season. Since they have been given the right amount of water and fertilizer, these plants will be ready to thrive in your garden.

Don’t be afraid to pick up a few that need TLC, they will get established and bring joy year after year.

Here’s a great one that doesn’t sell well, which I swoop in and get at the end of the season. Aralia ‘Sun King’ is a shade lover grown for its chartreuse foliage. It grows to three feet or so wide and tall. This plant is deer-resistant, carefree, and is a perfect addition to light up a shady corner.

The Lawn

For many, the grass went dormant during the hot, dry weather. As it returns, this is a good time to put some fresh seed down. The new grass will fill in and be more vigorous than the older turf.

Renting an aeration machine with the neighbor is a good idea too. It’s used to treat compaction by pulling thumb-sized plugs out of the lawn leaving holes. That also allows water and fertilizer to get down into the root zone.

A good balanced, organic fertilizer will get the grass ready for the winter and provide a lush lawn until the end of the season.

Shrubs and Trees

There are lots of sales going on for the shrubs and trees which have also had a home at the nursery for the season. It’s critical to match the right plant with the right place. Study the plant tag and trust it, knowing how big a plant will get and leaving room for it to reach maturity is smart gardening. Don’t think you’ll be trimming the shrub or tree to keep it in bounds, it’s always going to want to reach its genetic size.

Choose the planting site wisely, and also thinking about sun or shade. A dogwood or rhododendron will live out in full sun but is more suited as an understory plant.

The biggest mistake made when planting a tree is planting it too deeply. Before planting, brush off the soil near the trunk. The root flare should be visible when planting, it’s better to have that flare a little higher than lower.

Mulch that tree but never like a volcano, that will kill the plant. A mulch ring should never touch the bottom of a tree and resemble a donut, not the dreaded volcano mulch.

Get to know the people at your local nursery, they want to help you find the right plant. A friend of mine pointed me to a hydrangea which looked different than all the rest. Here’s a primer for getting hydrangeas to bloom.

Even though it was the same cultivar, this plant had some green and white variegated leaves. Not only was it less than half price, it could also be something completely unique. It was a great find and I’m anxious to see how it performs, and if those leaves continue to show variegation. I did offer it to my friend, but her collection is become unwieldly, she was glad to see it get a good home. This is often the case with nursery professionals and it’s better for everyone if the plant gets into the landscape instead of having to winter over at the garden center.

Tender Annuals with Bulbs/Tubers

It might seem counterintuitive to plant a dahlia, caladium, canna, elephant ear or tuberous begonia this time of the year, as the above ground growth will succumb to a frost. It’s a great way though to get instant color in a fading summer garden and the tuber or bulb can be saved easily over the winter or in some cases the plants will be happy on the windowsill.

Caladiums have beautiful foliage, love the shade, hate the cold. I bring containers in to grow on a plant table next to a large window for the winter. Elephant ears make great houseplants too.

Saving the bulbs or tubers is pretty simple and something I’ll address when the time is right.

This is such a wonderful time to be in the garden.

Get out there and get a few packets of seeds and some plants to keep the garden going strong and looking great.

Free Swiss Chard Seeds

When I put together Doug’s Free Seed Shacks this spring, I ordered way too much Swiss chard seed. It’s a variety called ‘Perpetual Spinach.’ It Belongs to the same species as chard and beets, but it’s different. It tastes more like spinach than Swiss chard.

If you would like a free packet of the seed, send a self-addressed, stamped envelope to:

Doug Oster
Swiss chard
P.O. Box 11013
Pittsburgh, Pa 15237

Aralia ‘Sun King’ is a little off the beaten path, but a great shade loving perennial to plant now. It’s carefree and deer resistant too. Photos by Doug Oster
Tatsoi is an easy to grow green from the kale family with a mild flavor.
Check out Doug’s offer for free Swiss chard seeds.
This ‘Fire Island’ hydrangea was different than all the rest, having variegated foliage. This is a great time to plant shrubs and find bargains at nurseries.
This caladium was on sale, in a pot with light green sedum. The caladium bulb can be saved over the winter and the sedum is actually a perennial, which will return on its own next season.
Lettuce is easy to grow from seed and can be started right now.


Doug Oster writes a weekly column for The Green Voice Weekly Newsletter. He also the host of The Organic Gardener Radio Show every Sunday morning at 7 a.m. on KDKA radio 1020AM. 

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