Are you thinking this because you want more of the same kind of plant? If so, I'd wait a few years before dividing these perennials... give them a chance to settle in and get used to their new home by spreading out roots, etc., and give yourself a chance to see if each plant is in the right spot. You'll probably be surprised at how much they do grow in one year. Absolutely true advice... worry more about the soil your plant is living in and less about the bugs you find. You'll never be able to get rid of all the bugs but you can search for ways to improve the soil and encourage natural pest control into your garden. Molie

It depends on the plant :-) I've divided some in the middle of winter (eg: hostas, daylilies, Siberian iris) with no ill-effect. OTOH, both agastache and penstemons tend to prefer really good drainage and sometimes have issues with our winter weather. Agastache in particular I would tend to leave be until spring and drier conditions. FWIW, the rule of thumb in the timing of dividing perennials is to divide early blooming perennials in fall and later season perennials in spring. But that's pretty general and there are always exceptions.

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I have successfully transplanted perennials, shrubs including azaleas and trees(in full sun too) in July with no negative effect. Like you say frequent watering did it’s job. Although I start suffering myself from digging when temps are above 85 degrees like you say Ken lol. I also have 2 more questions regarding this. Are so called perennials that produce new growth on old wood such as chrysanthemum pacificums, dracocephalum argunense classified as sub shrubs ? I know montauk daisies and caryopteris are officially considered as sub shrubs but there are no info regarding certain perennials such as dracocephalum and C. pacificum as sub shrubs. I’m sure there are many more perennials that grow on old wood. One other question. So dividing is considered a method of propagation. That practically means a new life is born. So if you divide a perennial does that start over the plants life? I know that they retain maturity of the parent plant but is that also associated with its lifespan? Let’s say I divide a columbine, a plant with a very short lifespan and let’s say it will only live for 5 years. However if you divide it and you decide to grow the divided plant, does that start over its life span and live for another 5 years? Or say that I decide to divide my 5 year lifespan columbine at 3 years old. If the lifespan does not renew does that mean the newly separated plant will only have 2 more years to live? The 5 years is just an example I’m using, I’m not saying columbines all have a lifespan of 5 years. Also please don’t say they reseed a lot to make up for it’s short life span. I’m already aware of that and that’s not what I want to know. I’m also curious if biennials like forgot me nots Renew their 2 years lifespan by dividing them..