glued gravel on top of plants?

16 years ago

Have you seen those bonzai trees with the gravel on top? I just realized that gravel is all glued together. Any idea what glue to use for a DIY (do it yourself) project?

I imaging it has to hold up with water going over it, has to let water go through it, and be non-toxic to plants.

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tapla (mid-Michigan, USDA z5b-6a)

last year

......... does the protagonist of this video prune his roots well? If that's the way he habitually root prunes all plants regardless of the degree of congestion, I would say no. For that particular plant, I would say it's fine. I'll explain.

The reasons for repotting, which includes root pruning, are to 1) relieve root congestion throughout the entire soil/root mass, 2) increase the volume of soil available for colonization by fine roots which do all the plant's heavy lifting, 3) increase the volume of soil capable of holding resources - water, nutrients, and particularly air. As roots grow they occupy soil pore space which can limit oxygenation even in well-aerated media.

The plant repotted in the video was what I would consider to be borderline insofar as whether or not it needed repotting. The soil/root mass barely held together and there were no heavy roots to be seen within the soil mass. Root pruning should focus primarily on removal of heavy roots not attached directly to the base of the trunk, and on removal of roots that are potentially girdling, circling roots, roots growing straight up, down, or back toward the center of the root mass, and crossing or j-hooked roots. There were some roots growing straight down in the video, but they hadn't reached the size where they served only as plumbing rather than an organ that was taking up their fair share of nutrients.

He also left the roots in the center of the soil mass to grow larger and for the root mass remaining untouched to continue to increase in congestion; so the effort was a bit closer to potting up than a full repot. Had I been doing the work, I would have sawed the bottom 2/3 of the root mass off, then used a root rake to comb the soil from the remaining roots before selectively removing the heavier and problem roots remaining. I think he would have done a greater service if he had worked on a seriously root-bound plant as opposed to one that wasn't in great need of a repot.

(see root rake bottom row 3rd from left, next to the saw. The tool next to it, to the right, is a root hook - useful for combing out heavy roots and digging away a badly compacted soil, the tool that looks like a sickle is for removing stubborn plats from their pots. On the bottom far right is a root pruner. Missing is a pair of heavy scissors.)

..... remind me if the crown or the roots should be pruned first in a ficus? First, allow me to say that a repot with root pruning is stressful to a plant; but the fact is, 2 weeks worth of stress during recovery from a root pruning is a drop in the bucket compared to the lost potential associated with prolonged root congestion. Plants regularly (fully) repotted with root pruning will grow to be many times the size of plants left to languish in pots completely congested with roots; and, they will be healthier all the while for the regular rootwork, all else equal.

When it comes to rootwork and pruning the you of the tree, I frequently run into well-meaning individuals quick to assert one should never prune the top when transplanting a tree "because the top is where the food to grow more roots comes from". You'll only hear this from folks unfamiliar with rootwork, and they're just repeating something they memorized, with no understanding of how plants work. Plants are very economical organisms. Plant central ALWAYS knows how much foliage it needs to support the root mass with food, and how much root mass it needs to provide water/nutrients to the top of the plant. What one does to the top causes a reaction in the bottom, and the reciprocal of that is just as true.

So, if you do a heavy pruning of the top, roots die back and the top regrows until the plant's chemical messengers inform the plant "we're good, we have balance". When you prune the roots hard, as one might in the first pruning session, it can cause the entire plant to collapse from an adequate supply of water. To see how ridiculous it is to suggest "one should never prune the top to balance the root to shoot ratio" Try lifting a tree in leaf in summer and see what happens. I have had opportunity to lift a number of trees from the landscape in summer, and have found the only way to prevent collapse is to prune them very hard or defoliate the plant if it allows. Repotting is something like lifting a plant in summer as you're leaving a large % of the root mass behind (by removing it), so it is entirely appropriate to ensure there is a reasonable balance of roots to shoots to prevent collapse of the plant.

That wasn't to say you should be overly concerned about killing your plants if you don't get the balance just right. It doesn't work that way. With potted plants, you can keep them out of wind in shade for a week or two which significantly reduces transpirational water loss. It's only when you do a really hard root pruning that you need to prune back the top. It would be unusual to have to prune back a houseplant unless you have a big 5-10 gallon tree and really want to reduce the roots significantly.

I prune my trees every spring anyway, to remove lanky winter growth, so I typically prune the top and roots of all but needled evergreens when I repot. This includes deciduous, tropicals, subtropicals, and broad-leaf evergreens except those that bloom on old wood. They seldom notice that they've even been pruned, pushing new growth within a week or less in most cases.

I've found it's best to prune the top first if you need to, and when you see back-budding just starting to occur, do the repot. I think the time frame would be prune top, then prune roots 2 wks later. The foliage removed reduces water demands on roots and the new growth just starting doesn't yet increase those demands. You'll have leaves already started and willing to grow, but the plant will suspend the top growth until roots recover enough to support continued maturation of the young leaves. It works equally to prune top and bottom at the same time if you were planning on pruning the top anyway. You'd have to take my word on that because you won't have the reassurance of the new branches starting to grow that you normally see if you prune the top 2 weeks before the roots.

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