Hi all, hope everyone is doing well. I have several maples I summer grafted in July of 2017. The rootstock had very stout root systems, and I’m certain are quite rootbound at this point. What time of year would be best to undertake this task? Thanks, Kyle
The more ambitious the work, the more important it is that it be done when the plant is in a period of strong, active, growth. Spring is that time. Most bonsai people do it when the buds begin to swell, and are successful. I do it after the leaves have expanded and have good luck, too. My thinking is, "Where does the energy come from to rebuild roots?" It comes from the leaves, so if the leaves are fully engaged, root recovery comes sooner. Where do leaves come from? They come from the energy stored in the roots, so if you do major work on the roots you are limiting the ability of the root system to inflate the whole canopy, especially from scratch. One word of caution: Keep the plant in high light, but out of direct sun until you see new buds expanding as a sign that the roots are strong enough to support the whole canopy. If you are worried that the plants may be rootbound, which can be terminal, then you can slip-pot them right now. You need a new container that is big enough such that you can put the whole rootball in the new pot without disturbing any roots and just add soil below the rootball and on all sides. You also get a look at them, too.
I am quite concerned they are rootbound. The rootstock actually had roots growing out of the bottom of the pots and into the ground (chalk that up to a lesson learned). I will plan on doing “surgery” on them in the spring then.
If the roots have escaped, they are "planted" for all intents and purposes. Leave them there, mulch with leaves up to the top of the soil line, and do your deed in the spring.
Hi Kyle, good to hear your grafts are doing well. If they're putting on roots, that must mean they're getting good energy from the grafted tops. I'd pot them up to larger sizes next June, after the initial flush of growth. I wouldn't disturb roots from 1/2 yr grafts more than necessary, just check for strangling (or eventually) roots, give a trim. cheers, -E
Although you were asking about root pruning on young grafts i have already changed my grafts which were bought in this year and have changed all the growing medium they were in and changed it to the one i have all my trees in. Yes i will keep my eye on the weather and move to more sheltered covered areas for protection if needed , here in the UK we tend to have more milder winters than you guys in the US but saying that we had the coldest winter for over 40 years this year and everyone survived. Also i do all of my pruning lifting and root pruning of my trees as of now , always have done and always will do works for me and that's all i can say on this, people might think it's wrong but it works for me and my trees, spent most of last week branch pruning (hard) and this week have started on lifting and root pruning and re potting. Pictures of trees that were done last fall first seven done from Sept to Dec then last two were done in June 2017, the only time i don't touch anything is in the spring , i just leave them all alone and let them flourish naturally, if it's a fit healthy tree you should never have any problems. You will get loads of different opions on how to look after JM and all of them will work no problems , it's just a case of playing around with different ideas and methods of growing and finding something that works best for you but most importantly your trees !! I have.
Pictures of how they coped over the winter and how they progressed into spring and summer. The last pic is of yesterdays trees that were lifted root pruned and repotted in new medium and done in exactly the same way/method.
Those are some nice looking trees, Roebuck. The buds are beginning to swell on my grafts. I believe I will let them flush, and not root prune till after the initial flush.
I have personally had bad luck doing major root work and/or repotting in autumn. The general/conventional wisdom for people like me where we have deep, long cold winters is that the energy stored in roots is what plants need to wake-up the following spring, and short-changing that process is problematic. My proof of that for me is my success rates of doing it in fall when plants are going dormant verses when plants are vigorously growing any time in the 3 months of spring. I prefer after the leaves have flushed out and mature, June, while many others do it in early spring when buds start swelling. That said, I wouldn't question that it may be that those with shorter, less intense winters may be able to do it in autumn. Tennessee is middling cold with shorter winters so it's a judgement call.
I absolutely second this view. Fall planting and root pruning is great if you can read the future and know that it's going to be a mild Winter. In reality you are taking a huge risk. I find it weakens the tree and impacts cold hardiness. This is amplified in container grown. Follow those who promote fall root pruning when you live in parts of zone 5 and 6 in the Midwest and you risk losing everything! (or areas that experience prolonged hard freeze below 20F, we see below zero For the down to -20f at times with many days at single digits) . We also see highs of 60F and plummeting lows below zero in 24 hours. Areas prone to sharp temperature swings should not risk it either. If you live in the northern limits of what you are growing, let things rest in autumn. Re-pot in spring as buds swell and the threat of freeze is over. Protect from early season frost.
Let me emphasize the last sentence above: Winter is bad enough as an agent of stress, but the real killer is a false spring. That is, a warm spell long enough to fool plants into budding out prematurely followed by weeks of cold weather. This is the culprit that kills whole crops of cherries and other tree fruits, and many, many individual plants that are grown marginally too far out of zone, or are weakened plants, and genetically-challenged cultivars like lots and lots of Roses.
I've been looking for this post for a while. I'm so glad we can go back and look at old post. Question for @ROEBUK , do you also move tree from the ground to containers between Sept/Dec? Or if anyone else move trees back and forth or have thoughts on when is the best time for them?
For cold climate adapted woody plants autumn is existing root elongation time (50% of the annual increase in length) and spring is new root production time. With summer being a secondary season for root growth and winter being effectively a period of hibernation. And roots cut in autumn not responding until spring. So that the traditional commercial production routine involving deciduous stock shipped bare-rooted to end consumers and retailers at end of winter after digging in November, storing in cold and humid conditions until shipping time is alignment with this schedule. A schedule determined by hormones generated by winter stem buds and sent to root tips - whenever these buds are present and fully formed the explosion of root elongation occurs. So that autumn in this context can be as early as July, in the case of drought affected vine maple (Acer circinatum, a relative of Japanese maple); opening of these same winter stem buds the following spring prompts production and growth of new roots. All this is why previously warehoused bare-rooted stock acquired and planted at end of winter can look like dead sticks at planting time, with when this material comes back to life later young shoots and roots appearing at the same time.
Thanks @Ron B . I was going to wait until leaf drop but I think I will go ahead and start the process. I will be storing them in my unheated greenhouse over the winter.
