Repot recovery in a grow tent? Maples

[MHBonsai]

I've got several Japanese maples waking up this month and pushing buds, and several are getting some severe root cutback re-pots this year. Transitioning from trunk grow-out boxes into smaller containers. The weather has been pretty mild with some days even hitting the 70's - but after this week temps are going to dip back into the 20's at night. I typically do the shuffle into the garage to protect the newly potted trees.

I have a tropical setup that I use during the winter season. It is a 4' x 4' grow tent with LED lighting, heating/fans and I hold it at a consistent 75 - 80 degrees and 80% humidity for ficus and other tropicals. It's kinda like this one. They grow like crazy all winter long. Love it.

As I'm shuffling trees in and out of the garage in the spring, I wonder if it would help with early root recovery if I just dropped the maples in the tent after repot and let them recover for a month or two, then bring them out once the threat of freezing has come and gone?

Or will this stress the maples even more putting them in an unusual environment? Would the added heat prompt better root growth and recovery in early spring? I know I've read that bottom heat after collecting large alpine trees is effective, as well as humidity bags - would this move the bar for recovery for a maple as well? Anyone do this for freshly potted deciduous trees?

Thanks,

 

[Mike Hennigan]

Let me preface my response by saying, I have no idea. It seems like overkill. But I think bottom heat will help most species grow new roots. And I think it’s possible that this could help but only if you can keep the humidity quite high. I put newly collected hawthorns into black garbage bags and put them into full sun to help them grow new roots. High heat/ 100% humidity. And it works really well. I don’t see why this wouldn’t help, but try it out knowing it could fail. The key in your setup as I see it is keeping humidity high and keeping an eye for fungal issues. I would probably spray a fungicide, maybe daconil, on the tree before putting it in there.

 

[Wires_Guy_wires]

Deciduous don't take the transition from LED/indoor to outdoors very well. I think they'll defoliate themselves as soon as they go outdoors due to the overdose of sunlight. LED's have come a long way, but they don't have the same wavelengths as the sun has.

It might be wise to buy a water proof heat mat and/or build a cheap plastic plant tunnel. That way they can keep going, without the indoor-outdoor related issues.

 

[BobbyLane]

you could try the old bubble wrap and gaffer tape technique

 

[Nybonsai12]

If they are leafing out and you have done the root work. I would simply protect from freezes and keep them in the garage, shuffling in and out on days when temps are safe. I would not put them in a grow tent.

 

[Leo in N E Illinois]

@MHBonsai -
I've seen and used a somewhat similar set up for orchids. I think your tent would be fine for the several weeks to a month before it is safe to put the trees outside. A refinement is if you could drop the temperature during the night to at least 10 F degrees from what ever the daytime high temperature. (drop about 5 C). The day-night temperature differential helps the tree to accumulate carbohydrates. But this is a minor thought.

When my Japanese maples would wake up early, even in the brightest light of my light garden, the new growth under lights tends to be lank, elongated, and weak. When it is time to put them outside, I have to put them into deep shade first, then after a week step them into part shade, then after another week step them into normal part sun that I normally grow them in. They burn up, especially the ones with yellow or orange early spring leaf colors. The spring red, or spring green seem to adjust to direct sun much more easily. Lost a Acer p. 'Katsura' due to moving into sun too quickly. After a few weeks in normal sun, I have to go back and cut off any weak or elongated stems that developed under lights. Do this early enough, and it will keep going. Do it before or beginning of summer.

Because of late frosts, I have now switched over to only one remaining JM and 2 Amur maples. The Amur maples never need protection, I just leave them outside.

 

[0soyoung]

I suppose that I am just being argumentative, but what would happen if the roots were packed in ice or kept cold in some way?

Growth is slowed to a crawl below 40F/5C so the ability to take up water is restricted which means that shoot extension from cracking buds will stall for as long as this is the case. It certainly works to stall azalea blooming.

Regarding repotted roots, the simple act of cutting them doesn't dispose of their frost resistance. Like above ground, the new growth is what lacks frost hardiness. Keep the roots cool, there is very little growth to get frost damaged.


IOW why isn't it a good idea to keep the roots cold through a temporary situation like being discussed in this thread, as opposed to keeping them warm, which we all 'know' is the right thing to do?

 

[MHBonsai]

Thanks for the replies everyone. Part of the reason why I’m asking is that I have had some pretty good success with other trees, and root cuttings. Crab apples, elms, Boxwood, and others have done OK in the grow tent and responded well to transferring outside in the summer. For what it’s worth, my lights are very bright and I have to watch not scorching trees. I get pretty tight growth for the most part.

These are all recent repots that have recovered for a month or so in the tent. I put them in with no leaves Late January. I can’t imagine getting this kind of growth if they were outside in 40° weather. Maples just seem more fragile to me however.

 

[MHBonsai]

@MHBonsai -
I've seen and used a somewhat similar set up for orchids. I think your tent would be fine for the several weeks to a month before it is safe to put the trees outside. A refinement is if you could drop the temperature during the night to at least 10 F degrees from what ever the daytime high temperature. (drop about 5 C). The day-night temperature differential helps the tree to accumulate carbohydrates. But this is a minor thought.

When my Japanese maples would wake up early, even in the brightest light of my light garden, the new growth under lights tends to be lank, elongated, and weak. When it is time to put them outside, I have to put them into deep shade first, then after a week step them into part shade, then after another week step them into normal part sun that I normally grow them in. They burn up, especially the ones with yellow or orange early spring leaf colors. The spring red, or spring green seem to adjust to direct sun much more easily. Lost a Acer p. 'Katsura' due to moving into sun too quickly. After a few weeks in normal sun, I have to go back and cut off any weak or elongated stems that developed under lights. Do this early enough, and it will keep going. Do it before or beginning of summer.

Because of late frosts, I have now switched over to only one remaining JM and 2 Amur maples. The Amur maples never need protection, I just leave them outside.

I overwinter several orchids in the same set up. They grow like crazy. I have to keep them shaded.

 

[0soyoung]

Just like growing tomatoes in short season climates ...