The What, When and How of Cloning Plants
Haydn Christensen has an interesting planting method for his many towers of mint.
If you were to walk through his greenhouse, you would notice that in the shallow gutters which run underneath the rows of towers, dozens of sprigs of mint have fallen and began to root out. This is Haydn’s quick and easy way to grow new mint plants, and it’s possible because mint has a natural inclination to clone easily.
Since seeing Haydn's clever trick, we've started propagating our mint in the same way!
Cloning can be a great option for many crops, as you don’t have to buy seeds and it can be done in unconventional spaces, like the gutters in your ZipGrow system. For many crops, however, genetic variety can aid in pest resistance, and some crops will sooner wither up and rot before they root out.
So when is it a good time to clone, and when is it worth buying seeds?
Here’s how to choose which crops to clone, and which to grow from seed.
When to clone?
Before you choose one way or another consider the following:
- Price of seeds. The price of seeds might be much less that the cost of cloning - or vice versa! Cloning can cost money in the loss of those crops from which you're cutting clones. On the other hand, some types of seeds can be quite expensive.
- Germination. You'll want to understand how quickly and easily the crop germinates from seed. If you are replanting towers of rosemary and you need 30 plants as soon as possible, but you have only 40 seeds, then you’ll want to clone at least some of the plants, because rosemary typically has a poor germination rate.
- Crop. Is the crop easy to clone? Some crops simply cannot be cloned. Most single-harvest crops and large fruiting crops, for instance, do not clone well. Woody crops and crops with smaller leaves on obvious stems, however, do much better.
Good for cloning: Mint, rosemary, basil, thyme, oregano, woody herbs, tomatoes and peppers
Bad for cloning: Lettuce, kale, chard, mustard greens, collards, bok choy, and some fruiting crops.
When in doubt, try it out! (And have some seeds as back up.) You might be surprised at which plants are able to root out.
- Pest and disease resistance. Many crops are able to develop defensive mechanisms to resist pests and diseases. If you have only one genome for a whole crop, this can stunt that process. (The weakness of the “mother plant” against a specific pest can be shared with the whole crop if they have all been cloned from that plant.) If you do clone many plants, make sure that you cut clones from multiple plants. If you only have one or two plants to clone from, borrow a few sprigs from a fellow farmer or a gardener nearby.
How to clone
Cloning is easy. For plants who have truly mastered cloning like mint, just cut the stems and put the stems in water. Mint roots out quickly and easily.
For other plants, I recommend buying a container of rooting powder, which acts as a hormone signalling the plant to root out. This can decrease the time it takes the plant to root out by weeks.
First, cut sprigs of the plant you wish the clone with a razor or sharp shears. A clean cut is better than torn stems or ragged edges.
Trim the edge of the stem so that it is cut at an angle. This exposes more tissue to the hormone and to access water and can make the process faster and more effective.
While the stem is still freshly cut, dampen the end against a damp cloth or in water, and dip it into the rooting powder. Most woody herbs with rooting powder root out in a week or so.
You can increase survival rates by wrapping the roots in a media to provide protection and keep the stems damp.
After wrapping the stem, keep the media damp (or the water at an appropriate level). A low-maintenance way to do this is to place a container with drainage holes directly in the gutter.
When you plant clones, make sure that the clone has a sufficient root structure to support the plants, and consider keeping irrigation constant for the first few days so that the vulnerable roots don't dry out.