Most folks know that spring is the optimum time to divide perennials, but some don't realize there are some perennials that benefit from autumn divisions.
Such as:
Perennials will give warnings to let you know that they would like to be divided.
Some signs to watch for:
- flowers get smaller, or reduced flowering
- sometimes the growth in the center of the plant dies out, leaving a weakened hole in the middle with all the growth around the edges
- plant loses vigor or leaves become yellow, browning in mid season
- plant starts to flop or open up needing staking
- may have outgrown its area
The trick is timing. Waiting until shorter days and cooler night time temperatures are key. The month of September is ideal in Southern Ontario. These perennials need at least 4-5 weeks to establish roots - in weather unhampered by heavy frosts.
I've even divided hostas and daylilies in a pinch this time of year.
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| Easy to chop portion of iris out with sharp spade |
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| Place rhizome clump on grass; divide further if you like |
Iris and Peonies have fleshy roots. They don't want to be planted too deeply. Once uprooted, divide the sections and cut out any dead or rotting bits that may compromise the plants. Cut back the foliage to about 8 inches for iris and for peony, to the lowest leaf node. This prevents further die-back (decay) reaching the roots and it evens out the above ground growth with the below the earth growth. It helps establish roots - setting well before winter arrives.
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| Cut back iris leaves to about 8 inches; remove any brown, damaged leaves and any damaged rhizomes as well. |
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| Peony roots have carrot thick root segments that meander all about. Dig deeply to remove as many roots as possible. Keep intact as many as you can. | | |
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| Here I divided the peony in two. Leaving only 1 leaf segment at the top. |
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| You may have broken roots that easily snap - not to worry. Look for these eyes that will produce shoots next season. |
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I've had peony come back with smaller roots than what you see above. However, they take AGES to flower. So it's best to make sure you have thick and as many roots unbroken as you can.
Be sure to keep iris shallow when planting. Some rhizomes should be visible from the soil.
Peony are tricky. Make sure they are not planted too deep. Flowering is hampered when the peony are planted too deep. Just make sure the roots are no more than an inch below the soil level.
