Plant Palette

Plant Palette

Planting Fall Perennials

Photo of Jennifer Schultz Nelson

Jennifer Schultz Nelson
Extension Educator, Horticulture

It seems to me that each year summer flies by faster and faster. Before we know it, there will be a chill in the air and our gardens will be asleep for the winter. September is the perfect time to take stock of what worked and what didn't in your garden this year. There is also still time to get a head start on next year's garden by planting perennials.

Take some time in the next month to take pictures of your gardens. You will be glad you did this January when the first spring garden catalogs fill your mailbox. It will be easy to decide if you really have the room you think you do for new plants. I am notorious for having eyes bigger than my garden, and having pictures on hand does provide a reality check.

Also consider what your garden looks like this time of year. Is everything looking tired and worn out by the summer sun? Consider adding some plants that bloom in the later summer and early fall. Just a couple of fresh new blooms can liven up the whole garden. Some of my favorites are Caryopteris, Aster, Joe-Pye Weed (Eupatorium), Sneezeweed (Helenium), Sedum, and Balloon Flower (Platycodon). These are just a few suggestions-- there are many more choices out there.

Maybe all your garden needs is a little rearrangement. Fall is a great time to divide or relocate perennials. Pictures can come in handy for deciding on where to move your plants. Sometimes just looking at a picture of your garden will spark and idea on how to rearrange plants that you didn't think of before.

One tip I've heard utilizes the power of picture editing software on the computer. Take a picture of your garden, including any significant landscape features, like trees, entryways, etc. On your computer, use the picture editing software to flip the picture around, generating its mirror image. It sounds crazy, but sometimes looking at the mirror image of the exact same garden will generate new ideas. I think it's because our mind gets used to looking at the garden as it is, and we don't notice the potential for improvement. A mirror image is different enough that our mind may notice design potential that was otherwise overlooked.

When relocating perennials in the garden, dig the plant out with a large rootball trying not to damage adjacent plants. Keeping as many roots intact as possible will help the plant re-establish itself in its new location faster. If you are dividing plants, try to keep as much roots with each division as possible. Again, more roots will help the divisions establish themselves quicker in their new homes in the garden.

The key in getting fall planted perennials to survive the winter is timing and mulch. The plant's roots need to grow and establish sufficiently before winter sets in. Though the ground doesn't typically freeze in this area until December or January, the cold temperatures slow plant growth, including roots.

The safest advice to follow is to plant your perennials no later than September. That way, temperatures are still warm enough to promote good root growth before cold weather hits.

Another point to remember in planting fall perennials is mulch. They need a little extra mulch for the winter, applied in late October or November. Just be sure to remove it in the spring.

It's really not necessary to fertilize fall planted perennials. That said, many people will still feel like they must fertilize fall planted perennials. If adding fertilizer will make you feel better, stick to fertilizers containing only phosphorus and potassium, to encourage good root growth. Nitrogen fertilizers will encourage leaf growth, and what is more important in the fall is good root growth to sustain the plant through the winter. Frosts will come all too soon and nip those leaves anyway.

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