Plants from Cuttings

    I prefer to grow most native plants from seed rather than from cuttings. However, there are some advantages to growing plants from cuttings. These include: (1) seeds might not be available or limited in amount, (2) cuttings preserve the unique genetic identity of the parent plant, (3) cuttings often mature sexually (i.e., produce flowers and fruits) quicker than plants grown from seed, and (4) for some species, rooting cuttings is much easier or faster than growing the plants from seed. I use three methods for propagating native plants from cuttings: (1) placing cuttings in a clear container, (2) placing cuttings in a mist chamber, (3) placing cuttings directly into the ground using a technique I call the DG-method.
Preparing and Potting the Cutting: Try to collect cuttings only from plants in good health and vigor. Plants with wilted leaves because of drought or plants showing other signs of stress (e.g., few leaves), generally, do not yield cuttings that root well or easily. Cuttings from cultivated plants often root better than those from wild plants. Whenever possible, I collect a cutting about one foot long. This allows me to trim and shorten the cutting later when potting. In the case of trees or shrubs, avoid cutting horizontal or descending branches because these will sometimes yield a plant that does not exhibit a natural shape (e.g., a sprawling shrub instead of an upright tree). Immediately place the cutting in a moisture-tight and rigid container containing a small amount of water to avoid wilting and damage. 
    Back at home or the nursery, prepare the pots first and then the cuttings. I generally use square or round pots instead of dibble tubes for my cuttings; I’m not exactly sure why except that I find them more convenient to stand upright and they visually remind me that the plant was grown from a cutting. Different horticulturists prefer different rooting media. I fill my pots with a 1:1 mixture of perlite and vermiculite or, for particularly easy to root cuttings, a 1:1:1 mixture of perlite, vermiculite and peat moss. This second mix is normally adequate for good growth until I plant out the plant; cuttings propagated in the first mix usually need to be repotted to another media mixture to get good growth after rooting.
    Wash the cuttings thoroughly with clean water. (I sometimes add a small amount of dishwashing liquid). While washing, look carefully for any insects and eliminate them. Remove any flowers or flower buds (they will divert energy away from developing roots) and any severely damaged leaves. Then, remove all the lower leaves until only the top 3-4 inches of the cutting has attached leaves. Recut the bottom of the cutting directly through a node about 6-9 inches from the growing tip using a razorblade for a clean, undamaged cut. Treat the bottom of the cutting with a rooting hormone. I typically use a 1:10 dilution of Dip’nGrow® but all the various brands of rooting hormone, powder, gel and liquid, seem to do the job. Gently place the cutting in a pre-made hole in the potting media (i.e., do not push the cutting down through the potting media since this could injure the freshly-made cut) so that at least two nodes are below the surface of the media and there still exists 1-3 inches of media between the bottom of the cutting and the bottom of the pot (i.e., do not place the bottom of the cutting at the very bottom of the pot). Some native plant growers will make multiple cuttings from one collected stem. I prefer not to do this for two reasons: (1) sometimes the stem-tip will produce hormones that aid in root formation, and (2) generally, a cutting with an intact stem-tip will yield an immediately more attractive plant.   

Prepared cutting in individual container. 
Method One:
I use a clear container to root cuttings when: (1) I have a small number of cuttings, (2) I’ve discovered the cuttings root better in a clear container than in a mist chamber (e.g., some native species have leaves or stems that rot quickly when constantly wetted), or (3) I wish to experiment and compare the two methods. The container can be any size depending upon the number of cuttings you are rooting; a single clear covered cup for an individual cutting or a large clear storage box for many cuttings. After placing the potted cutting in the container, spray the inside lightly with water and cover. Place the container in a bright but cool place. I normally place my containers under artificial light in my home. If you place the container outside be certain it does not receive too much sunlight or you will bake your cuttings. Observe the cuttings every day or so. Remove dead leaves, check for insects or fungus, and re-mist the container if it appears dry. Plants vary tremendously in the amount of time it takes for cuttings to root so I cannot tell you how long to wait. However, if the cutting retains at least some of its leaves, don’t give up on it. If it loses all its leaves, I normally don’t wait any more than two months before throwing it away. In any case what you’re looking for is new growth at the stem tip ⎯ new leaves or the growth of immature leaves. When you see this, give the cutting a very gentle tug to determine if it has produces any roots. A rooted cutting will not move when you do this. Alternatively, you can wait until you see roots emerging from the holes in the bottom of the pot. After the cutting has rooted, partially open the container for a couple of hours and watch to see if the leaves of the cutting wilt. If they do, reclose the container and try again a week later. If the leaves do not wilt, leave the container partially open. Then, after a week, open the container a bit more (maybe, one-quarter of the way) and observe the cutting’s leaves for wilting. Continue to do this until the container is completely open. You can then remove the rooted cutting and start treating it like a regular plant (e.g., more light, fertilizer, regular watering, repotting). 

Mist chamber constructed of PVC pipe and shadecloth. Closeup of misting valve.
Method Two:
Place the newly-potted cutting in a mist chamber and adjust the misting frequency so that the cuttings leaves do not wilt. For most of my cuttings, I set the misting for one minute of mist every ten minutes but this is just a rule of thumb for my situation (i.e., sea-level in Wai‘anae under 70% shadecloth). Observe and care for the cuttings as I described in Method One. When you observe new growth, check for rooting visible through the pot’s holes or with a gentle tug on the stem. If the cutting has rooted, remove it from the mist chamber and see if the leaves wilt. If they do, return it to the mist chamber and wait another week before testing again. When you no longer observing wilting when you remove the rooted cutting from the mist chamber, begin treating it like a regular plant. (Sometimes, rooting cuttings will wilt slightly but not severely when removed from the chamber. If this happens, it’s normally safe to start treating the rooting cutting as a regular plant. The wilting should disappear in a day or two.)

In-situ rooting with inverted cup and carpet.
Method Three:
This is a technique I originally invented for easy-to-root coastal plants such as ‘akulikuli and pā‘ū-o-Hi‘iaka out in Kalaeloa. I now also use it for easy-to-root dryland plants such as  ‘ilie‘e and kulu‘i or for in-situ transplanted seedlings. For restoration projects (and in the garden) the most significant advantage of this method is it eliminates the possibility of introducing a weed, pest or disease from the nursery into your field site. Start by digging a hole approximately one foot in diameter and 6-12 inches deep; keep the displaced soil directly adjacent to the hole. Fill the hole halfway with water and let it drain. Refill the hole with some of the soil you just removed, mixing it thoroughly with a small amount of water so that it is moist but not soupy. Continue adding soil and water until the hole is completely refilled with the moist soil. Using your finger, create a small hole in the center of the moist soil. Place your prepared cutting (i.e., cleaned, trimmed, treated with rooting hormone) in the hole so at least two nodes are below ground-level and secure it by gently firming the surrounding soil with your hands. Carefully, place a large plastic cup (with two small holes in its side to vent hot air) and carpet-square over the cutting and secure them by placing 4-5 fist-size rocks on the edges of the carpet. The cup will prevent the cutting from drying out while the carpet will keep the soil surrounding it moist. Check the cutting every week for new stem and leaf growth. If the soil appears dry, water the planting. Normally, after 2-3 weeks, you will see new growth which means the cutting has rooted and you can remove the cup and carpet. Water the rooted cutting and begin treating it as you would any new planting. Occasionally, if the new growth severely wilts in 1-2 hours, you’ll need to re-cover the plant with the cup and carpet; try uncovering the cutting again a week later. 
    For transplanted seedlings use the same method above minus the cleaning, trimming, and rooting hormone. As much as possible, try not to damage the seedling’s roots when transplanting; if you can get the entire seedling with roots in a shovelful of soil, that’s perfect. Transplanted seedlings normally require about a week to recover from roots damaged during the transplant. You can test this by removing the cup after one week and looking for wilting after one hour. If the plant’s leaves are severely wilted after the hour, recover the plant and test again a week later. If the plant looks fine or only has slightly wilted leaves, give a good watering and begin treating it as a typical new planting in your garden.

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