Author Topic: Mint Propagation  (Read 2856 times)

Offline I.L.W.

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Mint Propagation
« on: January 08, 2016, 06:11:00 PM »
Mint Propagation Basics

What is mint?

"Mint" is a name applied to many different plants. Most commonly it refers to those members of the Mentha genus of family Lamiaceae (Sometimes called the "mint family").
Lamiaceae is a large family of herbs, including all true mints, monarda (bee balm), lemon balms, basil, oregano, betony, nettle and many others. The most easily identified characteristic of this family is the square-shaped stems.

Within the Mentha genus, there are hundreds of cultivars like Spearmint, Peppermint, Watermint, Cat Mint, Chocolate Mint, Orange Mint, Apple Mint... and many others, most of which have no common name.

Outside of that genus, you will find things like Chinese Artichoke referred to as "mint" or "mint root". Many of these mints grow from small tubers, and should be propagated by division.

Growing from seed:
Mints in the Mentha Genus are notoriously bad at germination. Below is a seed flat at 8 weeks, with nearly 1,000 seeds planted amongst 72 cells. That's 13 seeds per cell. Of those, most have 2-4 sprouts at 8 weeks, many cells remain empty. That's less than a 25% germination rate in a climate controlled grow room with fresh, mature and stratified seed.

All mints can be grown from seed, however you will need to plant far more seed than you would for most other plants. As a rule, if you know the seed source is good, 1,000 seeds is adequate for 1 growing flat. If the seed source is of unknown quality, it's wise to plant at double that rate. This gets expensive very quickly and should be reserved for rare seeds in the genus which are not available as mature plants (as is often the case with imported cultivars like this one).

To obtain a large plant, you must prune members of the Lamiaceae family regularly. This is done by removing the primary stem above each new set of leaves. From the remaining terminal leaves, new stems will appear, turning one stem into two. Those two can be cut again with the setting of the next leaves, multiplying it to 4 terminal stems. Then 8, 16, 32... Ultimately the plant will adopt a bushy form with many fresh tips. This is important, as the tips are used for rooting new plants, and host the youngest, most tender and flavorful leaves. This makes regular pruning and harvesting essential. The more you prune and harvest, the bigger the plant will get.

Here is 4 day old cutting which has already rooted itself in a pot of coarse compost and begun putting out new growth.
The first set of leaves on the far right stem is blocked by the scissors in the photo, but there are leaves just below the scissors.

On the taller stem the leaves are very close together, so I have opted to prune higher on the plant.

To give you an idea of effects of pruning, here is a stinging nettle (also part of the mint family) which has been pruned in exactly the same manner just 5 days ago. If you look just below the cut, there are four protrusions. Two are the base stem of larger leaves, and two are new terminal stems which will put out leaves of their own.

Here's another specimen (Catmint) which is undergoing the same pruning method.

As you can see, the catmint plant is emerging from a single stem, not root suckers. The stem itself is becoming woody.

I'm sorry I didn't capture a shot of the catmint from farther back, but it has roughly 40 growing tips from the one primary stem. Each of these terminal stems remains very tender. This is important, as it will be used for oil distillation at the end of July, and only the freshest tips should be used.

Taking cuttings:
When  pruning, you may opt to let a growth tip put on 3 sets of leaves before cutting it off. Then you have a long stem, from which you strip the bottom two sets of leaves, and place it in a jar or shot glass of water to root. Change the water daily and it should have roots within a week. If you're not diligent about replacing the water, you can plant it 2/3 deep in a pot of wet sand. It will begin rooting very quickly.

You want light in the blue spectrum for mints to discourage flowering. If mints begin to flower, root production slows considerably, the oil content of leaves drop and production of tender leaves will nearly stop until after seeds have dropped. Blue light discourages this. I know it's a piss-poor picture, my camera shows the light as "red", in real life, there is only one red diode in it, but it is predominantly blue.

These LED bulbs are 14W (cheap to run for long periods). They cost about $20 online, and will sufficiently light four 1 gallon pots. Ignore the fluorescent lighting in the pictures, I just brought the plants into the grow to get better lighting for the pictures. Fluorescent lighting can be used, but remain vigilant on puning any flowers which will emerge under those conditions.

Doesn't mint spread easily by itself? Why do I need to propagate it?

Yes, established mint patches are very vigorous growers. Indoor propagation is used to get a head start on the season, to control pruning for a prolonged period (without winter die-back), and to provide you a source of fresh mint in the off-season (winter up north, summer down south) when it may not be productive outdoors. It's also useful for controlling cross pollination of two or more cultivars, as mint pollination is easily contaminated by insects carrying pollen from other varieties.

Expanding an existing mint bed:
After a few years, you may find that the mint bed has died out in the center, and is instead growing up in the lawn or garden in a radius around the original planting site. This is normal.

You can reinvigorate the bed simply. Hit it with a weed whacker. The stems will be strewn over the area. Leave them where they lay, or rake them to your choice location, and cover with compost, sand or mulch, then wet the area. Every cutting will root in place, and you'll have hundreds of new plants very soon.

Hydroponic Propagation:
This is one of the easiest plants to propagate hydroponically (or by any means for that matter). You need a cutting, a container, some water, and an aquarium bubbler. Fill the container with water, place the aquarium bubbler in it, float the cutting on top of the water. At every leaf node, just below the leaves, it will send out new roots. As the stem grows, each new set of leaves will have it's own roots. When you're ready to plant them in their final location, just trim the stems between the leaves, and you'll have hundreds of small plants.