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Perennials/pruning dipladenias


QUESTION: hello, I have 5 dipladenia plants whose runners are going crazy (they remind me of the "day of the triffids"!!) - because I live in southern ontario our night have already gone slightly below zero & I have brought the plants indoors - now I need to know how to prune these offshoots to try to tame them because at this point they are intertwining with each other because I have no other place to put them at this time - how far back can I trim the runners without stunting or killing the plants? I have checked so many sites but they only tell you how to trim, they don't actually show you - if you could show me where to cut the runners, how close to the plant and how often I would really appreciate it, thanks so much, Jutta

ANSWER: Hi Jutta,
Thanx for your question.  You can take the runners off at almost any point you wish.  It will not harm or stunt the plant.  At some point soon, this plant is going to go into semi-dormancy and not grow or bloom much as the height of the sun drops in your northern climate.  Just trim the runners off wheverever you wish.  Whatever makes the plants look tidy.  These are pretty tough, but tropical plants.  Growth slows down to almost zero during the winter.  Your specific quetion read, "how close to the plant and how often..."  I would just cut them back as far as it takes to keep them from tangling up and to make them look neater.  You can go all the way back to where they are coming out of a major stem and just snip them off. It will not hurt the plant.  Do this as often as you deem necessary but as I said above, the plant will drastically slow down growth during the winter.  I tried to find some pix of pruning mandevillea/dipladenia.  Let me know if my info clicks for you okay?

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QUESTION: Hello Tom, thanks so much for your help, at least now I know that I can trim the plants back without hurting them - one other quick question, during the winter months indoors how often should I be watering the plants? should I let the soil dry out or keep it moist & should I be feeding them while they are in their dormant state? these plants are totally new to me, I have never seen anything like them before, the blossoms are what caught my eye, they are just beautiful & the greenery is so thick & lush but boy, those runners are almost scary the way they grow so fast, even overnight I think they add on at least an inch of growth - anyway, thank you so much for your help, I will let you know what happens after I start trimming & I hope to hear from you soon, sincerely, Jutta

Hi Jutta,
Thanx for your question.  I would water the plants once a week but make sure the soil is not soggy.  Do not feed them during the winter.  They will go into a sort of "semi-dormancy" when the sun is lower in the sky, in the winter.  Keep them in an eastern or southern exposure windor.  They may end up looking a bit raggedy by the end of the winter.  When you take them back outdoors, be sure to place them in the shade for about 10 days to re-acclimate them to the outdoors.  In warmer weather, keep the soil moist but not soggy and feed with a fertilizer rated for blooming plants or a 12-12-12.  I hope this helps.


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Tom Alonzo


I have been a gardener for 20 years with perennials both growing from seed and from nurseries. I went through the Master Gardener Program from Kansas State University Cooperative Extension Service and I answered questions on the Hotline a few years ago for the Wyandotte County Kansas Extension Service. I have also lived in the Florida, California, Hawaii, Arizona, Texas, Kansas and Missouri and am experienced with a variety of climates, soils and weather conditions.


I have been growing perennials for over 20 years now. I am self-taught mostly except for a master gardener class. I have experimented with all kinds of perennials including many that are not common to my area. I have read hundreds of books and grown hundreds of varieties of plants and hope to make it a business some day. I have become versed in botanical names and growing conditions and what I don't know off of the top of my head I can usually easily find in my vast array of research material and botanical and horticultural contacts. I especially enjoy experimenting with growing plants out of zone.

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