One of the most popular (if not the most popular) bonsai trees, Juniperus procumbens ‘Nana’, serves excellently as a gift for anyone with an interest in plants and plant care. Juniper procumbens trees are becoming increasingly popular as an introductory plant to the ancient art of bonsai. Also known as the Dwarf Japanese Garden Juniper, or often just Juniper Bonsai, this southern Japan indigenous plant grows as a ground cover if left to its own. In its natural form as a wide and low shrub, Juniper proves its popularity by adorning office park landscapes around the world.
The ‘Nana’ cultivar/variety is both frost hardy and particularly slow growing. Because of its natural low and spreading growth habit, it can also be easily trained in cascading and windswept styles as a bonsai tree. It’s in the name! Procumbens refers to the plant’s procumbent, or prone and prostrated, nature of growth. Juniper is a great choice for bonsai beginners because of its hardiness and ease of training. Ironically, they’re not as popular in Japan because some bonsai enthusiasts consider them to be too easy! That being said, the Juniperus procumbens ‘Nana’ bonsai plant is not like a normal houseplant – it still needs a bit of deliberate TLC to keep it happy and healthy. Follow these pointers, and you’ll have a happy tree in no time!
Indoors or Outdoors?
There’s no way around it. Juniper bonsai will grow more vigorously if kept outdoors where light and moisture are more abundant. Outdoor bonsai care is an all-around easier road to travel. If you have the resources, it’s my official recommendation that a Juniper bonsai be kept outdoors. In virtually all temperate regions of North America, Juniper can be kept outdoors with minimal supervision.
This doesn’t mean that Juniper can’t thrive indoors, especially during the winter if the plant is undergoing winter dormancy (more on that later). The trick with proper indoor care is lots of light, hydration, and especially humidity. Light and water are the two most common ways people mess up caring for Juniper Procumbens, so make sure you dial those two in for the happiest, healthiest plant. With modern technology and horticultural practices, any home hobbyist can tick all the boxes. Growers that postulate the notion that Juniper procumbens can’t be kept indoors are, frankly, not keeping up with the times. The rest of this article will be primarily for bonsai enthusiasts who wish to keep their Juniper procumbens indoors.
This plant loves bright light. Six or more hours of very bright or direct light is essential. Outside, we shoot for full sun exposure. Ideal placement would offer morning sun and afternoon shade. Morning sun is strong yet gentle, whereas afternoon sun can be unnecessarily harsh and hot. The east, south, and southeast sides of one’s house are safe bets.
If you don’t have enough natural light coming through your windows, consider supplementing with a grow light. LED grow lights are becoming ever more popular as technology becomes more powerful, compact, and energy/cost effective. If you are using an artificial light source, however, make sure you let your plant have natural periods of light and dark rather than leaving the light on all the time – they need their beauty rest too! Popular lights often have timers built in, but standalone wall-socket timers are similarly easy to find online or at any big box garden center.
Soil should stay consistently moist – not overly wet, constantly soaked, or soggy. Shoot for watering when the top soil begins to dry out somewhat, but there’s still moisture down below by the roots. Our Juniper bonsai product comes with a decorative gravel layer and an accent mineral which can be easily lifted to check on moisture below the soil line. Consistent moisture is key. Depending on your local humidity and temperature, whether or not you use a humidity tray (which you absolutely should), how often you mist the foliage, or if you keep the plant outdoors in the spring-fall, this could mean watering almost every day, or as little as once per week. If the soil ever dries out completely, the foliage will become brittle – sometimes irreversibly so. Conversely, if the soil is kept soggy for too long, root rot can set in.
Water until water starts coming out of the bottom of the pot. Most growers soak the bottom of their pots in their sink or a dish of water to thoroughly saturate the media without risk of disturbing the top dressing. When watering in place, I find it convenient to use a misting bottle liberally to hydrate foliage and soil all in one go.
Use your best judgement to work out your own watering interval. Prioritize monitoring soil moisture rather than watering like clockwork on a weekly schedule.
On Juniper’s endemic Japanese island mountainsides, humidity never drops below 60%. Indoors in the winter, most of our households will hit the low 30% range. Humidity goes a very long way with long-term health and keeping the foliage from turning brittle. I strongly recommend the use of a humidity tray and humidifier if keeping the plant indoors full-time.
Potting & Soil
Juniper can tolerate a lot of various soils, but to be truly happy, they need a fast draining bonsai style potting media. While these bonsai trees are super thirsty and love moisture, they’re also highly susceptible to root rot. For this reason, bonsai purists prefer to use media composed of akadama, pumice, and lava rock. Inorganic mixes also help stunt growth – it’s all part of the art of bonsai!
Compacted, clay heavy soils will not work. Generic all-purpose potting soils, which are usually based in peat moss, will retain far too much moisture and contribute to root rot. Locally available soils marketed for bonsai are often perfectly acceptable. These soils are loamy and full of peat moss, but are also heavily amended with sand and bark to reach that high level of aeration that most bonsai prefer. There are many bespoke potting mixes on the market designed for a wide variety of bonsai. Juniper’s soil requirements fall under the umbrella of most varieties, so if you’re unsure where to start, don’t be afraid to grab the bag labeled “Bonsai Soil” off the shelf of your nearest garden center.
The soil we use for our Juniper procumbens nursery stock is a bit more moisture retentive and contains more organic material than standard. We like it this way so we can offer longer watering intervals and reduce the time investment required to keep plants hydrated and well-fed.
Here’s our recipe:
30% mixed organic soil
30% pine bark and pine bark mulch
Repotting is important to maintain nutrient uptake while encouraging your tree to stay small. Juniper bonsai need to be repotted about every two years while they’re still young. Repotting intervals will grow longer and longer as a plant matures. When the root system begins to bind around the edges of the pot, it’s time to go for it! Don’t be afraid to unpot your tree to inspect root development.
It’s not always necessary to pot up in size. More often than not, it’s best to trim away part of the root system and re-use the same pot. Remove the tree from it’s pot, rinse off all the soil and cut away root mass from the sides and bottom, being careful not to remove more than ¼ of the root ball altogether. This keeps the plant bonsai size rather than shrubby and overgrown. Target any damaged, brown, or unhealthy roots first. Late winter or early spring is the best time to repot your plant – just when new growth is about to start after its winter dormancy. If you’ve been using organic fertilizers in order to promote symbiotic bacteria growth, leave some of the original soil behind so that they have an easier time replenishing. Be careful to not directly fertilize freshly trimmed roots in the month following a repotting session. Juniper benefits from foliar feeding in general, so using diluted liquid soluble fertilizer on foliage after repotting will help the plant establish more quickly while the roots are too fragile for standard fertilizer.
Fertilizer is best applied as a Juniper enters the growing season in spring. Apply a general purpose 20-20-20 fertilizer for extra vigorous growth. Applying it in spring will help jump-start its ability to produce new healthy growth, but if you’ve recently repotted your bonsai, as mentioned above, be sure to wait two to four weeks to apply any fert directly to the root ball. We recommend using time-released organic fertilizer to simplify things for you and keep fertilizer uptake more consistent while also encouraging growth of beneficial bacteria and fungi. Mycorrhiza fungi develop a symbiotic relationship with a bonsai tree’s root system by transferring nutrients to the plant while the plant in turn releases sugars for the fungus to feed off of. Do not fertilize in winter or during dormancy.
Juniper procumbens trees undergo a natural winter dormancy that lasts about three months. Start preparing your plant for dormancy just after Thanksgiving. After eating all of that turkey, you’ll probably be ready for a nice long nap as well! This dormancy can be completely subverted if you’re able to provide warm, bright, and moist conditions year round. Bonsai enthusiasts in tropical climates like Florida don’t exactly have the option of winter dormancy, and their trees grow perfectly well regardless. Growth will naturally slow either way, but the choice is yours. Many growers who keep their plants outdoors for the growing season will choose to bring their bonsai indoors during the winter. Semi-heated garages and sheds are popular choices for overwintering. Sheltered and shadier outdoor locations work too, so long as rain and snowfall is still available.
A cool environment is essential to the dormancy process. Depending on your climate you may need to protect your tree from the coldest days and harshest freezes of winter. While Juniper is technically cold hardy below 0°F, it’s best to avoid sub-freezing temps. Hydration and humidity are still of utmost importance, but light requirements drop off significantly due to the lack of photosynthesis and foliage growth.
Pests & Diseases
Remember, your juniper is not a houseplant, but a diminutive tree, so the pests that may afflict it are a little different than some other plants you may have. Red spider mites are the biggest single pest threat to a juniper bonsai. To check for them, place a piece of white paper under your tree and gently shake the foliage. If you see lots of little dots that move on the paper, you probably have a spider mite infestation. This can be treated with insecticidal soap or a neem oil solution fairly easily.
As previously discussed, overly wet conditions can cause root rot. Rotting roots must be removed. There are fungicidal sprays on the market to help out if you suspect your juniper is suffering from a fungal infection. One popular household remedy is the application of powdered cinnamon, a natural antifungal agent.
If you’re unsure of what’s afflicting your tree, be sure to isolate it from your other plants in case we’re dealing with anything infectious.
Training & Pruning
So much of the aesthetic of a bonsai is intricately tied to the detailed cultivation, pruning, and styling of each plant. The best time of year to prune and style your bonsai is at the end of its dormant season in late winter/early spring, but if you need to repot your tree as well, you probably want to wait to let it recover from the repotting for a season before you do any drastic pruning or articulation. The very, very long tradition of cultivating bonsai means that the sky and your imagination are the only limit in terms of pruning, pinching, and training the branches and foliage of your tree. Training itself is a super in-depth topic best discussed at length in another article.
Don’t be intimidated by the level of care your Juniperus procumbens needs. Juniper bonsai are relatively easy plants to care for when you’ve tucked a few bits of essential knowledge under your belt. So much of being a good steward to your bonsai tree is using your common sense and better judgement. Pay attention to changes in your tree’s health and appearance. Your tree will let you know what it wants if you know how to look for the signs! Go slowly and be a bit methodical in caring for it, and it will give you many years of pleasure and beauty.
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