How to Grow and Care for 'Sea Green' Juniper

There are dozens of species, hundreds of cultivars, and many hybrids in the genus Juniperus that all seem to deliver a different form, color, size, or hardiness. One of them is the popular but niche hybrid, Juniperus × pfitzeriana 'Sea Green' or plainly sea green juniper. The popularity of this fast-growing little juniper is all about its form and ease of care.

Sea green juniper is a ground-covering shrub that grows to about four to six feet at maturity, upright in the center but with a gently cascading habit towards the edges that makes it appear to spread wider than it grows taller. Besides its unique form that can lend itself to any landscape, it is highly valued because of its extremely high environmental tolerances. Once mature, the sea green juniper can survive with little care, making it a favorite coniferous shrub in gardens across the country.

Sea Green Juniper Tree Care

The ease of care required to keep a sea green juniper thriving is a huge part of its appeal. Once it is placed in a good location and has been cared for properly through maturity so it can establish itself, the level of care becomes dependent on environmental factors. If the juniper is getting the proper sun and water and is not bothered by pests or disease, and you do not want to worry about pruning to keep a certain form, it can be a plant-it-and-forget-it shrub, if that is your style.

Light

Sea green junipers are best suited for full sun. When living outside their native range, shade can cause excessive moisture to accumulate on lower branches that can cause fungal issues. Additionally, if it gets too little sun it will start looking scraggly and thin instead of having lush, full branches. While completely healthy, it will appear to lack vigor and not be aesthetically pleasing. Do yourself and your juniper a favor and place it in a place that gets full sun so you can get the most out of the plant.

Soil

The sea green juniper is rather adaptable to soil. Gardeners will need to adapt to the soil by changing their watering habits. If planted in heavy, dense soils, you will need water less; if planted in lighter soils, water more. No matter the soil, it should be well draining and have a slightly acidic to neutral pH. It can be easily tested with a simple home test or an inexpensive store-bought version and fixed with additives like lime if the soil is too acidic or aluminum sulfate if too alkaline.

 Water

The easiest way to ensure a sea green juniper fails to thrive is to not give it enough water as its establishing itself. Once the shrub matures, it is pretty hardy in most growing regions, besides the driest areas and during the worst droughts. Until that point in time, the most important care that can be given to a sea green juniper is watering.

For the first year after planting, giving the ground around the base of the shrub weekly soakings that saturate the soil is a must. Giving the sea green juniper one long saturating irrigation rather than daily fast-and-frequent watering sessions is important. Adding 2 to 3 inches of mulch at the base of the shrub to the drip line will also help the shrub retain any moisture from irrigation and rain.

Temperature and Humidity

With its wide-ranging hardiness zones of USDA 4 to 9, it is clear that the sea green juniper can tolerate various temperatures and climates quite well. Ideally, it prefers a middle ground, with a temperate climate being the goldilocks zone, to produce a truly happy shrub.

Fertilizer

When planting the sea green juniper, its hole can be filled with good quality organic compost, which should provide plenty of nutrients to give the shrub a great kickstart to help root establishment and help supplement and enrich the soil.

If a sea green juniper in your care looks unwell, poor soil is unlikely to be the cause, but testing the soil is certainly a place you can start since any deficiencies can be remedied by adding supplemental fertilizer. Testing aside, if you want to go forward and just fertilize your shrub, you will not cause an issue using a fertilizer pre-formulated for conifers; you can find several of these sold prepared in the form of slow-release spikes you place in the soil at the base of the plant.

Types of Sea Green Juniper

'Sea green' juniper is a cultivar of a hybridization of two different species of the genus Juniperus, J. chinensis and J. sabina. This means you will not find any other types of Juniperus × pfitzeriana 'Sea Green'. You may find the original plants used to create the hybrid, but this will not give you the desired qualities of the cultivar that breeders have selected through propagation.

Pruning

Most likely the only time the sea green juniper will need pruning is when its cascading form needs to be shaped or the height needs to be tapered back a bit. The key to successfully pruning this selection is moderation since the appeal of the sea green juniper is its cascading form. Prune too much away and that dramatic fountain effect is lost.

Pruning a sea green juniper is simple and requires only a few tools. Gather gloves, a pair of pruning shears, and alcohol, or a water and bleach solution diluted 10:1, to clean your shears. Plan to prune in the early spring before new growth arrives, trimming the ends of branches while still trying to maintain a downward arch. Clean the shears and properly dispose of the refuse.

Propagating Sea Green Juniper

Being a hybrid, the only way to propagate sea green juniper is to reproduce the plant from semi-hardwood cuttings asexually. This little project is not that hard and requires a bit of time, a few tools, and patience.

Gather your tools and materials, rooting hormone, a clean knife, the sharper, the better, a deep pot with drainage holes (big enough for a few cuttings since some might not make it; losses are acceptable), and a stick or something you can use to poke a few holes in the soil. Fill the pot with a mix of pre-soaked vermiculite and perlite.

1. Find a branch about 1/8 of an inch in diameter with new growth and cut about 5 to 7 inches of new growth off of it.
2. Remove the needles from the bottom two-thirds of the cutting and scrape away the bark exposing the fleshy part of the branch.
3. Cut the end of the cutting at a 45° angle.
4. Use your stick to poke holes into your potting mix for your cuttings.
5. Dip your cuttings in your rooting hormone and let soak according to the product's instructions.
6. Keep the potting mix moist and in a cool, indirectly lit area. It can take six to nine months for roots to become established.
   
7. Once roots have been established, transplant them to individual pots and let roots establish in those pots for at least a year.

Common Pests & Plant Diseases

One of the most appealing aspects of the sea green juniper is its ability to resist cedar apple rust, which plagues many other plants in the Cupressaceae family. It does deal with slight problems such as occasional blight on its branch ends, which is dealt with by readily available pesticides and being careful not to overwater.

Pests are a rarely seen issue in this selection. If there's an insect it's falling victim to victim to, it is usually the nuisance visitor: the bagworm. If the problem persists, these unwelcome guests can be easily removed by hand and treated with a topical pesticide. Overall, the pest and disease problems that the sea green juniper face are not serious, and if your shrub looks unhealthy, the issue will most likely be found elsewhere.