If purchased for the garden, shooting star hydrangea is usually planted in spring as a container-grown nursery specimen. Also, small potted specimens are sometimes sold during the holiday season as flowering plants in much the same way as poinsettias. Because these seasonal plants are often forced to bloom out of season, you’ll need to provide them with nurturing care if you want to continue to grow them through the winter to move outdoors in the spring. As a garden plant, shooting star hydrangea is a fast-growing shrub that you can expect to live for quite a long time. Be aware that hydrangea is mildly toxic to humans and pets, containing a cyanogenic glycoside called hydrangin, which can cause digestive upset if the flowers, leaves, or bark are consumed. If you want to experiment with changing the bloom color, you can blend in aluminum sulfate to the soil around the shrub to lower the pH and coax blue blossoms from the plant; or blend in agricultural lime to raise the pH and encourage pink blossoms. Soil amendment is best done in late fall or early spring. Shooting star hydrangea may require some annual simple pruning to keep it looking its best, but neglect does not ruin the plant. For cold-region gardeners who grow it in a container, shooting star hydrangea is one of those rare deciduous shrubs that can be moved indoors for the winter months to continue growing. But this takes special handling and is not always successful. You will need to keep it well pruned so it does not become too large to move indoors. The potted plant should be kept outdoors as long as possible, as coolish weather causes the plant to set flower buds, which may encourage the plant to bloom through the winter. But it is critical that the potted plant be brought indoors before freezing weather arrives. When the plant first moved indoors, put it in the coolest location you can find, then gradually acclimate it to normal room temperatures. During the indoor months, give the plant a spot with plenty of bright indirect light, but keep it out of direct afternoon sun.
Light
Shooting star hydrangeas kept in the garden do best with a partial sun position. They don’t appreciate continuous direct sun and benefit from shade in the afternoon. If you must grow them in full sun, they will require more frequent watering.
Soil
A well-draining and moist (but not wet) soil works well for this plant. It grows best in slightly acidic soil, which produces the iconic white flowers with just a hint of pink. Severely acidic soils will cause the flowers to be notably blue, while the flowers become pinker as the soil pH moves toward neutral or slightly alkaline. It is possible to tinker with the flower color by carefully adjusting the soil pH through amendments.
Water
Your shooting star hydrangea will appreciate regular watering. When grown in the garden, they will require a minimum of 1 inch of water per week, either through rainfall or irrigation. During hot, dry spells, the weekly water allowance should be about 2 inches per week. Dividing the total water allowance into two smaller waterings will help the soil remain consistently moist. When planted outdoors, adding a few inches of organic mulch can help to retain the moisture that these plants prefer. Although shooting star hydrangea prefers moisture, make sure you don’t allow the soil to become water-logged, and keep mulch back from the main stems. If growing a shooting star hydrangea in a container, water heavily whenever the very top layer of soil feels dry. Water thoroughly until water drains out the bottom of the container. If you move the plant indoors for the winter, maintain a weekly watering schedule.
Temperature and Humidity
As a garden plant, shooting star hydrangea is hardy in zones 5 to 11, but it may struggle in exceptionally hot, sunny locations. It is fairly sensitive to cold, and winter temperatures in zone 5 may cause it to die back to the ground, though it usually comes back in the spring. In the colder parts of zone 5 (5A), you may need to protect it with a burlap wrap for the winter.
Fertilizer
Feeding your hydrangea with a balanced slow-release fertilizer in the spring as new growth is starting can encourage a full bloom. Avoid too much fertilizer, as this can reduce flowering by forcing the plant into more vigorous foliage growth at the expense of flowes. In alkaline soils, using an acidifying fertilizer can force the plant into producing blue flowers that some gardeners crave. Avoid high-nitrogen fertilizers, as this often reduces flowering. It’s best to avoid feeding after late summer.
Pruning
Shooting star belongs to the group of hydrangeas that flower on old wood, so it is critical to keep pruning to a minimum and perform it immediately after the flowering period is over. Pruning in spring or too late in the fall can sacrifice the previous season’s wood and kill the current season’s flower buds. Deadheading flowers past their best and pruning back only spent branches after the blooming season will help to encourage new, healthy growth the next season. With a potted plant that must winter indoors, it can be challenging to keep the plant at a size that fits indoor spaces. Prune back individual stems as the flowers fade, and try to avoid hard pruning too late in the season. Keep the plant as large as is practical for the indoor space it must occupy. If pruning is done carefully, it’s possible that your hydrangea will continue blooming over the indoor winter months.
Propagating Shooting Star Hydrangea
It’s possible to propagate this plant by taking softwood cuttings through the summer months. Here’s how to do it: Note: While the ‘Hanabi’ cultivar of H. macrophylla is not itself trademarked, this shrub is very often sold in a commercial trademarked form, identified by a secondary registered name, such as ‘Fireworks®’. Such trademarked plants cannot be propagated legally by any means—vegetatively or by seed. Propagating a trademarked form of any plant can potentially create legal problems if you are discovered.
How to Grow Shooting Star Hydrangea From Seed
There are several reasons why seed propagation is not recommended for this plant.
First, this is a nursery-created cultivar with seeds that do not “come true” to the parent plant. If you collect and plant seeds, they are likely to revert to a previous genetic ancestor and will not be identical to the parent plant.Second, hydrangeas can take several years to reach flowering maturity. Since branch cuttings generally reach flowering maturity within a year or two, there’s little point in propagating from seeds.Finally (and most important), this plant is very often sold in a registered trademark form, such as ‘Fireworks®’. It is illegal to propagate this plant in any way.
That said, Hydrangea macrophylla in its pure species form is not terribly difficult to grow from seed, though it is quite time-consuming. Dedicated amateurs may want to try it as an experiment. Seep propagation involves a classic method of sowing the seeds in trays, keeping them moist and bright for about 14 days until they sprout. thinning out the seedlings, then planting in individual pots when they are large enough—a process that altogether takes about 14 months. Once potted up, the seedling needs to grow for at least another year or two in its container before it will be ready to transplant into the landscape. Remember, though, that seeds from named cultivars probably will not “come true” to the parent plant, and if the form is copyrighted, it’s illegal to propagate it.
Potting and Repotting Shooting Star Hydrangea
This hydrangea cultivar can make a good permanent outdoor container plant in mild climates, and in colder climates where they are not hardy, potted plants can be grown outdoors during much of the year and brought indoors for the winter months. However, although this type is smaller than some hydrangeas, shooting star is by no means a dwarf variety. It can develop into an unwieldy 5- to 6-foot plant unless you keep it sharply pruned. This can be problematic if you live in a region where the potted plant needs to be moved indoors for the winter. Shooting star hydrangea generally does well in a large, well-draining container of any material, using any good quality peat-based potting mix. Heavy clay or ceramic pots, or whiskey barrels, are a good choice because they are heavy enough to prevent tipping. If you plan to grow it permanently in a pot, it’s a good idea to move the nursery plant immediately into its new home. Select a large pot, as these plants can reach heights and widths of up to 6 feet. You will know it is time to repot when the plant’s growth and flowering begins to slow down. At this time, you can either pot up to larger container; or removed the plant, prune back its roots, then repot in the same container using fresh potting mix. This is generally necessary every four or five years—provided you have started with a relatively spacious pot. Potted plants that are purchased in winter as seasonal indoor plants usually have been forced into winter bloom, and it can be difficult to keep these alive through the winter. Keep the plant moist and in a location where they get plenty of bright but indirect light. Unlike many plants that require less water during winter, hydrangeas need to be kept quite moist over the winter months. With such a plant that has been purchased as a winter bloomer, it’s a good idea to move the plant outdoors in the spring and transplant it into the garden or into a more permanent patio pot. This is not a plant that grows well as a permanent indoor houseplant. And remember that the shrub will revert to its natural bloom cycle (summer to fall) if it survives its first winter indoors as a forced-bloom plant.
Overwintering
In colder regions (especaily the northern parts of zone 5), this plant can be prone to winter dieback unless it is protected with a burlap wrap. This, along with a heavy winter mulch over the root zone, usually is enough to keep the plant returning each spring. Such measures are not generally needed in zones 6 to 9. If you are growing the shrub in an outdoor container, gardeners in cold regions outside the hardiness range will need to bring it indoors or into a sheltered location for the winter months.
Common Pests & Plant Diseases
For most growers, shooting star hydrangea is largely trouble free, but there are both pest and disease issues that can arise. Aphids and scale are by far the most common insect pests. They are rarely fatal but can cause disfiguring defoliation. Hard water spray sometimes is enough to dislodge insect pests. Or, use a horticultural oil such as neem oil to control the pests. Often, though, simply leaving things alone will allow helpful insects to eventually control the damaging pests. Hydrangeas can be subject to quite a number of fungal leaf spot diseases, ranging from the white dusty coating caused by powdery mildew to Cercospora leaf spot and the brown splotches of anthracnose. You can minimize these problems by watering through ground-level soaking rather than overhead spraying, but during humid, warm weather, it’s very hard to avoid all fungal diseases. Severely affected leaves should be removed and destroyed. Widespread disease may call for spraying the plant with fungicide every two weeks or so. The best fungices are those containing the active ingredient mancozeb or chlorothalonil. Your best chances for control are to begin using fungicide as the disease is just taking hold.
How to Get Shooting Star Hydrangea to Bloom
Hydrangeas can be maddening shrubs for gardeners who demand consistent blooming each year. They are temperamental shrubs that on any given year may withhold blooms for reasons that seem mysterious. In the right conditions, shooting star will bloom from early summer to early fall with huge clusters of white flowers. But on the years when the shrub withholds its blooms, it’s likely for one of these reasons:
Improper pruning: These plants flower on “old wood” that developed during the previous season’s growth. If you prune the shrub too late in the year (or too early in the spring) you will remove all the growth that fuels the season’s flowers. Thus, it’s critical that any necessary pruning be done immediately after flowering. Wrong sun exposure: These plants prefer some early morning sun, then shade during the hottest part of the day. They often withhold flowers if they get too little or too much sun. It’s not uncommon for hydrangeas to bloom wonderfully for several years, then suddenly withhold blossoms if there are changes to sun exposure—such as growing trees increasing the amount of shade, or removed trees suddenly causing the hydrangeas to experience too much direct sun.Inadequate moisture: Hydrangeas require a just-right watering routine. Soil needs to be consistently moist but not soggy. During periods of drought, the plant’s foliage may look fine, but flowering may disappear almost entirely.Too much fertilizer: It’s quite common for hydrangeas planted near turf-grass lawns to get overfertilized with the high-nitrogen fertilizers that form the standard diet for lawns. Cutting back on lawn feeding may return the shrub to normal flowering. And hydrangeas should not be fed after August. Immaturity: A small, young nursery plant may simply be too immure to produce blooms. Be patient, as it can take two or three years for hydrangeas to bloom if they are immature when they are planted.Winter damage: An unusually cold winter, or an unseasonal cold snap in spring, may kill off the flower buds for the upcoming blossom season. Unless the frost has been very severe, the shrub will usually return to normal flowering the following year.
Common Problems With Shooting Star Hydrangea
Hydrangeas can be quite free of cultural problems in the right circumstances, but there are some issues that commonly arise:
Drooping Leaves
While drooping leaves on some deciduous shrubs is a sign of serious fungal disease of the roots, with hydrangeas it almost always signifies that the plant just needs water. If all leaves are suddenly drooping, a good soaking can restore the shrub within minutes. On the other hand, if the drooping seems confined to selected stems, this might be a sign of some serious fungal disease.
Yellowing Leaves
Yellowing leaves can be caused by several things:
Too much water can sometimes drown roots and prevent them from taking up soil nutrients. This is not common for these moisture-loving plants, but it is sometimes seen during exceptionally wet weather, especially for plants growing in dense, poorly draining soil.Lack of nutrients can also cause this problem. Like any large-flowering plant, hydrangeas need a fair amount of fertilizer early in the growing season. If you’ve forgotten the recommended routine of a slow-release fertilizer applied in spring, your hydrangea may remind you by causing the deep green leaves to turn yellow.Soil pH issues can sometimes result if you have been adding lime or aluminum sulfate in an effort to tinker with flower colors. If you’ve moved the soil pH outside the recommended range, the plant may protest by turning its leaves yellow. Proper leaf color is usually restored if you make efforts to move the soil pH back to the optimal slightly acidic level.
Leaves With Burned Edges
If the leaves show browned edges, this is usually the result of over-fertilization. It will rectify itself after regular watering leaches some of the excess nutrients out of the soil. Hydrangeas are best fertilized in early spring, then left alone. Fertilizing after mid-summer often results in fertilizer burn.
