Come February in South Devon it will be repotting time usually, depending on the weather of late, your trees are racing ahead and bursting forth and you are behind with your repotting!
Whether it is a deciduous or conifer tree, spring is the time that our trees start to wake up after the winter dormancy period, and start to actively put on new growth. To ensure the best outcome, we need to try to do repotting and the spring prune prior to leaves actually bursting, or buds are “just” breaking. It is to do with the amount of stress that you are putting on a tree, and as it is actively growing, it will heal and be invigorated post prune and repot.
These two pictures show a pine being planted into a large piece of preserved wood. First a suitable soil mix is added, wires are anchored to the wood and will be tied over the tree’s roots to hold it steady. The tree will need to settle and grow before any styling is done.
Only a few years ago, maybe up to ten years ago (time flies!) we all used to repot our trees every few years, but this has changed, it is now felt that we don’t need to repot our trees for many years if they are more mature, unless they are a vigorous species and are pushing themselves out of the pot by the amount of root growth.
If you have been a regular visitor to the site, and I thank you, then you will realise that we have repotting on the agenda every year. Despite what I have put above, all our trees are at different stages, so there is always one tree or another that needs its repot every year, and as we often have a new member or two joining each year, it is important that we cover the basics. Below, is what I wrote last year. Yes, it is very lazy of me, but if you can’t improve on perfection, then why try?!
There are a variety of reasons why you may repot your tree. It may have been in a training pot but is now ready for its own bonsai pot; perhaps it needs re-positioning in the pot to enhance its effect; perhaps your tree actually needs a holiday from the pot it has been in for some time; or perhaps you need to keep the roots in check. Your trees do not necessarily need repotting each year. The older your tree is, the less vigorous its growth. All trees like a slightly different mix, so it is best to read up on the best soil types for your tree. Most people have a soil mix for their deciduous trees and a soil mix for their coniferous trees, but what makes up that soil mix differs for each person! The one thing that is important is a soil which can drain freely. When repotting a tree, the general rule of thumb, is to remove a third of the root. Don’t just hack off the outside third, tease away the soil and loosen the roots around the outside (the outside third) and then you can ensure that you are trimming away the longest roots. Trim any damaged or unhealthy looking roots off, also any particularly thick roots which you do not need to form the nebari (the layer of roots leading from the trunk which show above the soil). This allows you to have space for new soil in the new pot, and also ensures that the roots grow outwards not just round and round. It is not wise to feed your bonsai for at least 6 weeks after repotting, mainly because some of the feeds can be quite strong and those tiny, new, white feeder roots just beginning to extend can be burned by the strength of the fertiliser and that could be fatal for your tree!
If you are not repotting your tree, do not think that you can ignore that tree. It is a good idea to scrape the old surface off the top of the soil and replace with a fresh layer. Not only does it look nicer, but it is removing any fungi etc lurking in the soil. Also, give the tree’s pot a nice wash, again it just looks like you care! Lastly, but not lastly, we all freshen up each day, so why shouldn’t your tree get a spring clean too? A soft brush like a toothbrush (an old one!) and some water will do wonders for removing algae off the trunk and branches. Pay special care around new shoots, as I wouldn’t want to get the blame if you scrub them off by accident!
Trees do not like being fed for at least 6 weeks after repotting to give your trees roots a chance to establish, especially if you use liquid feed as these can be quite strong and will burn any newly growing root tips.
Insects/bugs: As the weather warms up as does our bug life! Now, please do not think that I am anti bug, they are essential to our ecosystem and are pretty much the base of every food chain. But some, especially when in confined spaces like our trees’ pots can wreak utter havoc. Take the vine weevil, it is not uncommon to find vine weevil grubs (the hungry things that can strip a bonsai bare of all its fibrous roots) as early as February in Devon. It is therefore imperative that especially if you are not repotting a tree, that you treat your trees with Provado soil wash. At our Society we have found little else to keep on top of these pesky pests! If you are repotting, then check your trees roots carefully for little white flecks or larger white grubs with yellow heads. If you spot even one, then you need to carefully go through every part of the trees soil to ensure you get every single one out. To assist our little bird friends, robins are particularly partial to vine weevil grubs, so if you put the grubs outside in an open spot, they’ll soon be eaten! Make sure you put all the grubs in a deep pot though, we can’t have them wiggling off to pastures new! If you have a lot of grubs, the birds may not spot them in time, they are amazing climbers, so you may need to resort to killing them yourself!
Styling/Pruning: On deciduous trees, it is a good idea to do any major styling before the leaves have fully broken. This is because the sap in a deciduous tree is particularly strong, and some trees visibly “bleed” when cut, especially maples. To overcome this, cut any major branches before the leaves break. If you are a bit late, then using a wound sealer (available from most bonsai stockists) can help. Pinching out the growing tips on most species, encourages the tree to re-group, and often helps to produce smaller leaves. On species such as oak, removing the dominant bud when there are usually 2 smaller ones behind it helps to keep the leaf size down. Wiring is best done before the leaves break too. mainly because there is less to try to avoid! Be careful though, as buds are very easily knocked off!
Most of all, Spring is a time to rejoice in the end of the dull, damp winter. Well the dull winter anyway! It is a very busy time of year for bonsai growers. I hope this guide has been useful. I have only attempted to cover the essentials. If you have more specific questions, why not pop along to our next meeting, there are always members willing to answer your questions however silly you think it is! You will find the dates on the Diary of Events page.