How to winter tropicals and container plants

I need help knowing how warm to keep my greenhouse over the winter if I want to keep things like hibiscus, coleus, caladiums, double impatiens, fuscia, and begonias. Every spring I spend a fortune on these plants and I'd rather just keep them alive than throw them out or keep the rhizomes. But this is our first full winter having the greenhouse, and so I wondered about:

What temperature?
How much do I water?
How do I care for plants that usually aren't kept over winter?
Are there any plants that just don't do well in your experience in a greenhouse?
Can you keep tropicals and others together in the same greenhouse with the same temperature?

I would appreciate answers to any of these questions. Thank you so much!

Allie, what kind of GH do you have?

I will go ahead and offer some answers...

Most of the plants you mention won't die as long as the temps are above 32-40F, however, they won't live very well, either. I think it is safe to say that most people overwintering plants like these keep a min temp of 50-60F. The higher the temp, the more forgiving the plants will be with regard to watering...and the better they will grow.

Some plants, like caladium, like a dormant period. You have to respect that. Cut down on the water and give them a chance to rest. I have caladium in a ground bed, and even with water (to all the other plants in the bed) the caladium goes dormant, only to reliably reemerge in the spring.

Hard to answer your question about watering, as this depends on the plant, the temps, and perhaps most important, the growing media. If you have plants in GH soil (permanent beds), they are very forgiving when it comes to watering. OTOH, plants in containers are at your mercy. I prefer a coarse potting mix that drains well and requires watering more frequently...my basic mix is 60% bark or CHC, 20+% perlite, and less than 20% peat. I will water every 3-7 days using this mix. Plants in straight Promix or similar bagged peat-based mix are at higher risk of root rot.

My experience is that mealybugs and whiteflies like just about every plant you mention. I treat my containerized ornamentals with imidacloprid (Bayer Advanced Tree and Shrub) off-label, 2T/gal, with good results. I use foliar applications of Neem, permethrin, pyrethrin, or soap spray in combination whenever I find a pest problems.

With control of pests, enough heat, and the proper amount of water, you should be fine with the plants you mention.

What are the "other plants" to which you refer?

Thanks! My greenhouse is an inexpensive (relatively!) plastic covered house with a heater. I used it for seedlings this spring with great success.

The others are the plants I mentioned above - the impatiens, coleus etc (which I do not consider tropicals). Thanks for your advice. I find white flies to be the worst thing about over wintering plants (I've overwintered plants in my house before this). Oh- the other thing I want to keep are my lantana plants.

So, you think I should re-pot the plants in something a little less "soily"? (I know, not a word!) Could I mix regular potting soil and perlite together? I have both of these on hand.

Allie, for the best container plant thread on the internet, read this: http://davesgarden.com/community/forums/t/719569/
and part 2: http://davesgarden.com/community/forums/t/527353/

Lantana, impatiens, same advice.

Is your greenhouse made with rigid plastic panels (ideally twin wall polycarbonate), or is it one of those ones that's covered with flexible plastic film? If it's the latter, you may have a hard time keeping the temperature warm enough for some of your plants to really be happy. In my climate, I could overwinter tropicals in something like that, but in a climate where you actually experience winter, they tend to be great for getting a head start on seed starting in the spring, but they're not good for much beyond that.

I agree. You might be able to make a thin, single-layer plastic type GH work with a layer of bubble wrap.

I have a rion 8 X 12, and I overwinter everything in there. Banana plants, Hibiscus, EE's, rice paper plant, 3 hanging baskets, Brugs and whatever else I have. I just have a small Black & Decker heater, and have it set on frost setting and everythings does quite will. There has been times at night it has gotten down to 38 in there and never lost anything. But I am sure it never stayed that low for too long of a time. Then during the days there has been times I have had to open the doors because it was getting too warm in there. I do different then a lot of people. I water all my plants regular, just enough to keep the soil damp maybe once every two weeks. This way my hibiscus still bloom every now and then, they do loose most of there leaves and my brugs even will bloom at least once during the winter. I haven't had to much of bug problems either, of course I use scan mask which helps in the aid of spider mites. Last winter I did have some ants, I need to figure out how to be rid of them this year.

But you just have to experiment for yourself to see what works best for you or should I say your GH.

SB-you really think that plants in a peatbased soiless mix are at a higher risk of rootrot than a barkbased medium? I think I will respectfully disagree here-and here is why.

It is my opinion that bark based mediums retain water better than a straight peat/perlite'vermiculite medium. In fact, just this am I was filling some flats for ornamental kale and I mixed some bark mix into the peat mix so I wouldnt have to water them as much. Have been doing that a lot with plants that suck up more water.
Because a peatbased medium drains faster (and needs watering more), there is less chance for rootrot. Rootrot comes from the soil (or soiless medium) constantly staying wet, and in the winter,when the sun is not as strong (and the grhouse is not as hot), and the plants are in semi-dormancy-the soil is more at risk for not drying out. This also applies for the summer when the risk of rootrot is at its highest (pythium and phytopthera -the two rootrots love heat and humidity).
I know that you love to build up the soil for long term pots, as do I, so I am not saying not to use bark in a medium-but in terms of higher risk-I would say it is the bark based that is the higher risk. Of course, the risk lessens with either medium if you grow your plants on the dry side-just let them dry out before watering. Allie-that last statement was for you! lol

Allie-I would ditch the potting soil totally and move to a better draining medium-such as Promix or anything similiar ( there are many other companies that make a soiless peatbased medium that are much cheaper than Promix)

As to your lantanas and other annuals-they will do fine over the winter. I would think about moving them up to a larger size container for the winter, as they are probably rootbound by now, and rootbound annuals are harder to carry over the winter. I would also cut them back to about 4" from the bottom and take cuttings off the tops and get more plants. Lantanas and coleus are both very easy to do cuttings of.

For whiteflys, I would get a horticultural oil and Neem oil and alternate between them for spraying. It takes about 5 weeks of spraying every week to get rid of them. Be sure that you can spray underneath the leaves to get them. Spray in the early am when the adults are sluggish (they are underneath the newer leaves) and the larva are under the oldest leaves.

I keep tropicals and annuals in the same grhouse and they are fine. I keep the thermostat at 60 degrees because I am always propagating or germ seeds and I need the heat for that. 50 degrees would be ok, but some of your tropicals would start to go into a dormancy.

Well, plastic film is all I have, so I guess I'll have to try it anyway. I won't be getting any other kind any time soon. If it doesn't work, I won't lose anything, as I would have probably thrown the plants out anyway.

Has anyone had any luck overwintering in a plastic film greenhouse? I would appreciate any insight on that...As that is one of the reasons we got a greenhouse.

Do any of you overwinter in a sun room? I hope to have one of those in the next year or two.

TL, IMHO, the risk of root rot is related not to how much water the mix will hold but instead inversely to how much air it will hold. Peat tends to compact and loose its porosity, reducing aeration and resulting in a higher perched water table in the container. The bark, with larger particle size, has more macroporosity and will retain the structure longer than peat.

To be truthful, even bark breaks down faster than we would really like...CHC and Turface hold water well and will retain their structure in long term plantings much longer than bark will. I haven't used Turface (I promised myself that I would try it, but I haven't gotten around to it), but I use CHC a lot.

lol are you respectfully disagreeing with me??? I agree with the above that you said, but thats not what I have a problem with, with your original statement. The important factor with rootrot is not how MUCH (sorry for the caps-forgot how to do the darker print) water the medium will hold-its how FAST it will get rid of the water. Peat drains faster than bark, and with fungus-its all about moisture. or lack thereof. You couldn't pay me to put a bark (or CHC) in my medium that I grow pansies in, because of the fear of rootrot.

I wish I could get it together to order CHC off the internet-I truly would love to have it for my palms and tropicals. Let me know how the Turface works if you ever try it.

Hi tigerlily,

I am new to this thread and find the comments interesting. What is CHC? I am rooting cuttings of Million Bells and other annuals and also my Dipladenia and Mandevilla Vines to overwinter in my basement under lights and wanted to know the best mix to use. I have done the Million Bells already in perlite and peat and one is doing great so far. Hope it will do well under lights as I have never tried this before and I do not have a greenhouse but I sure wish I did.

Betty-when you say that you use peat and perlite-is it already mixed in a big bag or are you buying the peat moss and perlite separately and mixing them together? The reason that I ask is because the straight peat moss has a very low PH ( around 3 or 3.5 -very acidic-too acidic!). When you buy the soiless mix that has the peat and perlite,and sometimes the vermiculite mixed together, they also add a lime charge to combat the low PH of the peat and that brings the PH up to around 6.2 or so. That is what I use to start all my cuttings in, and also what I germinate a lot of seeds in as well. I like it too.
When you are doing cuttings-keep the soil consistently moist (I usually water them once or twice a day) and good bottom heat (essential in the winter esp). In the summer, bottom heat is not an issue so much. Once the cuttings root-then come off the water some, water only in the ams and let the soil go dryer at night so the roots will grow better ( water displaces oxygen and roots need oxygen to grow-also they grow at night so that is why I water in the am and let the soil dry out thru the day)

Thanks tigerlily,

I have been using the Miracle Gro peat that has perlite in it and then I add more perlite. Is this right? Also what is CHC? I also got a bag of Miracle Gro starter for seeds and used that on the Million Bell cuttings a few days ago.

Betty

CHC is coconut husk chips.

We may be talking about two/three different things here. Rooting cuttings, young plants, and long-term plantings all take a little different mix, IMO.

For cuttings, I use 50:50 peat:perlite, pH be da**ed. My results are as good as anyone else, I think. All of these are under mist. The soilless mix that Tigerlily uses stays way too wet on my mist bench, and cuttings rot.

With short term plantings and young plants, compaction won't be a problem...those plants will be grown and potted up before the mix has a chance to compact...so the peat-based bagged mixes are suitable...I'm talking about Promix and varieties thereof...they are as high as 70% peat.

Long term, 6 months or more, these bagged mixes will compact. This is less a problem in the summer, and more a problem in the winter, to get back to the original post. Temps cool, growth slows, water uptake drops, evaporative losses drop, and before you know it, you have rot. In this situation it helps to have a mix that maintains it's structure and porosity. Large particle size is key, I'm talking about particles BB sized, maybe larger. These particles can be bark (sorry, TL), Turface (fired clay, holds it's weight in water), CHC (holds something like 5-7 times its weight in water) Perlite, grit (I used medium turkey grit from the farm store) or whatever.

Good day!

Hi stressbaby,

That is what I have started my cuttings in --50-50 perlite and peat.

I was just curious what CHC stood for. I did try the Tapla formula to make one pot last July as an experiment and I used Miracle Gro potting soil in all the other pots. The pot with Tapla's formula is still looking pretty good . I will post a picture.

I have never tried to root cuttings until this year and I am having fun. Hope I can keep the cuttings looking good under lights through the winter. Do you suggest I turn fans on the plants?

lol SB-you are so funny!

The reason that my cuttings don't rot in the peatbased soiless mix is because I don't put them under a mister. I water them once or twice a day and that is it. I do about 15,000 cuttings a year that way. I really don't like excess water in a grhouse. I do put pansy seeds under a mister system in the summer though. Whatever works for you is what works! Part of the fun/agony is trying something and seeing if it works and if not-trying something else.

Thanks to both of you, I am enjoying the reading and both of you are experts and I am just a novice trying to learn .

Betty

lol Betty-don't mind SB and myself-we are just having fun with each other. As you well know-females have a greater percentage of being right and SB is a male-need I say more? Hey-ask him how his beloved Michigan team is doing right now. Think they are having "prolonged practices" this week??? lol Of course my Panthers are playing their first game this weekend-I can only hope they don't lose as bad as Michigan did last weekend. Its going to be a long season if they do...

SB where is a good source for the CHC? I tried that this summer because I got some bales from my SIL and I liked it. I couldn't really find a vendor though.

I am going to try to keep some plants in the gh this winter. Mine is a 6x8 HF GH so I thought I would caulk the air leaks and maybe put some bubble wrap in it. What is an economical heater to use? Last year I tried a radiator oil type heater and it cost a fortune($60 a month) so I quit that pretty quick.

I have passionflower and Brugmansias I want to keep in there. Maybe some palms and EE.

I lost my Physocarpus 'Diablo' you sent me. Maybe try again next year? The abelias are growing like crazy though. Thanks for the seedlings.

SB's a Wolverine fan? LOL!

Man... Now I gotta rethink this whole image-thing....


=D

dylangc, I have one left! dmail me your address again, just in case I lost it before, and I'll send it to you.

I'm ignoring you Appalachian State fans...

Go Block O!

=P

lol before last weekend, I don't even think anyone had even heard of App State, let alone be a fan of them!

Go K-State