Table of Contents
Introduction
Black diamond crape myrtle plants are known for their stunning colors, as well as for being low maintenance, and tolerant of many different climates and conditions. You can get them as shrubs or as upright trees, and they can be grown in borders or in containers on patios.
They also come in several different shades, including white, red, and purple, and their foliage is a beautiful dark burgundy. They are very popular for all these reasons, so we’re going to cover how to grow them and keep them happy in your garden.
The black diamond crape myrtle requires a good, sunny spot in a reasonably warm climate. They will not grow well in cold parts of the world, but are fairly hardy when it comes to temperature fluctuations. They like plenty to drink and eat, and will produce gorgeous flowers for a long season once they are well-established.
Indoor vs Outdoor Growing
Black diamond crape myrtles are not really suitable for growing indoors. They go dormant in the winter, and they require this period of dormancy to remain healthy; if you bring them into the constant, controlled temperatures of a house, they may not survive because they will lose this dormancy period.
However, if you are growing a black diamond crape myrtle in a cold climate and you do need to bring it in for the winter to keep it from freezing, you can do so (provided it has been grown in a container). However, you should not tend to them as you would a house plant, and don’t bring them into a warm part of the house.
An unheated indoor space will protect them from the worst of the cold. You should only move them once an early frost has killed back the leaves. This is the trigger for the plant to turn dormant. Once it has done so, you can transfer your plant into a shed or garage to keep it safe from hard frosts that could kill it.
You should stop fertilizing the plant (it won’t need food while dormant) and only water it every four weeks or so. Don’t panic if the plant looks dead; it is simply conserving its energy. When spring comes and the weather warms, start putting it outside during the day, letting it acclimatize to the outdoor conditions. Bring it in at night.
You should see growth starting up again; you can then start watering and fertilizing it more regularly. Once it is accustomed to the outside space, move it back outdoors until the next winter.
If you live in a warmer climate, you should not need to bring your black diamond crape myrtle indoors at all; it will manage even cold winters outside.
Best Location For Your Black Diamond Crape Myrtle
These plants are great for being noticeably adaptable about where they grow and how they grow. If you live in USDA zones 7 to 9, they will be happy outdoors year round, although if you live in other zones, you will have to take steps to control their ambient temperature if they are to thrive.
They like plenty of sun, so when choosing a spot for your black diamond crape myrtle, take this into account. Six hours of direct sun each day will make them happy; they will not thrive well in shady, dark spots. Less sun than this may lead to a sickly plant that struggles to grow and does not produce such rich foliage or blooms.
If you live in a cold part of the world, make sure you also choose a sheltered spot for them. Do not plant them somewhere windswept and open, but aim for the warmest part of your yard that you can find. This is likely to be reasonably close to the buildings and to other plants that will provide some shelter from the wind.
Some people in zone 6 may manage to grow black diamond crape myrtles as a perennial, with the plant dying back to ground level each winter. If you decide to attempt this, use a dwarf variety that will grow thick and bushy, rather than a tall variety that may become leggy and spindly as it attempts to gain height each year.
Soil For A Black Diamond Crape Myrtle
These plants like well-drained soil. They prefer to be planted somewhere that their “feet” will dry out well, rather than sitting in moisture all the time. They are more drought-tolerant than flood tolerant.
If your garden is mostly made up of heavy clay, you may find it’s necessary to add grit and sand to the soil to grow a black diamond crape myrtle plant. This should be dug into a fairly wide area around the plant, especially if you have chosen a large variety that will have big roots.
If you just plant it in clay, it will probably die as a result of waterlogging. The black diamond crape myrtle needs reasonably good drainage in order to survive.
Loamy and sandy soils are good options, so if you already have these in your garden, you’re in luck. The black diamond crape myrtle prefers a soil that is neutral to alkaline. You might want to get a testing kit and see what the pH value is before planting your black diamond crape myrtle; it likes to be somewhere between 5.5 and 7.5.
To increase the pH value of your soil, add a little lime; this will help to make it more alkaline. These plants won’t thrive in highly acidic soils, so it’s worth checking and making alterations if necessary.
Watering Your Black Diamond Crape Myrtle
In your plant’s first year, it is important to water it very regularly. It does not yet have an established root network to draw from, and it will be vulnerable to drying out, especially during hot weather. You should aim to water it once a week, and water deeply, rather than shallowly. This means standing and continuing to water until the soil is thoroughly soaked.
Deep watering will encourage your black diamond crape myrtle to push its roots down into the soil to capture the moisture. Shallow watering can result in a shallow root network, which will leave the plant more vulnerable to drought in the future.
You should aim to water for about half an hour to ensure that enough water really has soaked into the ground. Keeping about a four foot diameter around the tree clear of other plants will help to reduce competition and ensure that it gets enough water and nutrients.
You may also want to mulch the surface of the soil; this will help to trap moisture on the surface and minimize evaporation problems. Add a thick layer of straw, leaf litter, bark chippings, or something similar to keep the water in and make sure your plant has plenty to drink.
Once your plant is well-established and has deep roots, it will rarely need watering, except possibly in very dry and long summers. A strong black diamond crape myrtle should be able to go for months without being watered, provided it has a good root network.
Black diamond crape myrtles that have been planted in containers are more likely to need watering during dry spells, as their roots will not go so deep down, and they won’t be able to pull moisture up from the depths of the earth. They are still reasonably drought resistant, but they will need watering occasionally.
Humidity For Your Black Diamond Crape Myrtle
You probably don’t need to do anything to alter the humidity levels for your black diamond crape myrtle. Because it’s growing outdoors, not indoors, there will already be a reasonable amount of ambient humidity to keep the foliage fresh and vibrant.
Watering regularly will add a bit of humidity as the water on the surface of the soil evaporates, but you don’t need to go out there with a spray bottle every day. The humidity range in the black diamond crape myrtle’s growing zones should be enough to keep the tree happy and healthy without input from its owner.
Fertilizing Your Black Diamond Crape Myrtle
Like all plants, black diamond crape myrtles appreciate being fed, and not feeding them could lead to a lack of flowers and foliage, as well as slower growth. They will take up much of what they need just from the soil, but it’s a good idea to keep this topped up with plant food to ensure your black diamond crape myrtle is growing at its best.
In the spring, when the myrtle’s leaves are just starting to sprout, give it a dose of high nitrogen fertilizer to offer it a boost for the coming flush of leaves. You can repeat this in two months, ensuring it has plenty of energy for its whole growing season. Remember, black diamond crape myrtles have a long flowering season, so they need a lot of food.
When you have first planted your black diamond crape myrtle, you should use a general purpose garden fertilizer, such as an 8-8-8 or 10-10-10. This will ensure the plant has a good balance of everything it could need.
Feed it every month from March through to August, using just a small amount of fertilizer each time. A teaspoon spread around the perimeter of the plant’s newly dug hole should be enough. Water this in, and watch your plant grow!
Once your plant has got established, you should change your fertilization approach. An adult black diamond crape myrtle should be fertilized once per year, in March. You can use the same general purpose fertilizer, and around one pound per hundred square feet should be sufficient to give your tree everything it needs.
It’s important to water in fertilizer so that you know it has been washed to the roots (where it is needed) and also to avoid any chance of burning your plant with concentrated fertilizer sitting around on the surface of the soil.
You can either fertilize just before it rains, or use a hose to wash the fertilizer into the soil. Do not fertilize your plant excessively; you will end up with a lot of leaves and very few flowers, or simply a sick plant suffering from root burn.
If you have applied too much fertilizer, wash as much of it as you can away with plenty of water, and keep doing this for several days to try and minimize the damage.
Toxicity
If you have pets or young children, one of the first things you usually check before planting anything is whether it is toxic to animals or people. This is particularly important if you have a puppy or a young child who doesn’t yet understand the risks of eating certain plants.
Fortunately, black diamond crape myrtle plants are not toxic to either pets or people. It is probably not advisable to let your child or dog consume the plant in large quantities, but it shouldn’t do them any harm if they eat a small amount, or if they get the pollen or petals on them.
Some myrtle plants even produce edible fruits, and the family is generally considered one of the safe things you can add to your garden. You should still make efforts to keep pets and children from eating it, but it shouldn’t pose any dangers to them.
So, as well as having beautiful blooms and a long flowering season, coupled with stunning foliage, these plants are safe for you, your family, and your animals to have around!
Propagation
Like all plants, black diamond crape myrtles can be propagated, but this is often a very slow way to get such a plant. Because they will eventually be quite large, with some kinds growing up to around twelve feet high and five feet wide, you probably want a big space for this plant, and you probably aren’t going to want to wait years for it to fill it.
They are reasonably quick growers, but even so, it will take a long time for a seedling to become a mature tree. Often, people prefer to purchase young plants from nurseries or garden centers because they are already partially grown and will therefore fill the space more quickly.
However, if that isn’t an option for you or you really want to try your hand at propagation, that’s fine too. You can collect the seeds from a black diamond crape myrtle after it has flowered, or take a root or stem cutting; all of these methods should, in time, produce a new black diamond crape myrtle.
1) Seed propagation is one choice. Once your black diamond crape myrtle has finished flowering, it will produce berries, which will turn into seedpods. These will then split open, allowing the capsules to ripen. You can collect them, dry them, and plant them the following spring.
To plant them, get a container filled with damp compost or potting mix, and gently press the seeds into the surface of the soil. Add a layer of sphagnum moss on top, and then transfer the whole container into a clear plastic bag.
This should be placed in a warm, bright location (around 75° F) and left for a couple of weeks. Within three weeks, the seeds should have germinated. Water gently to keep them damp, and nurture the young plants.
2) Root cuttings can be dug up in the early spring, and gently cut off the main root using sterile secateurs. Plant a root cutting in fresh compost and put it in a warm, bright location. Mist the soil regularly and wait for the cuttings to sprout. Once the new plants are well established, they can be planted in beds or in larger containers.
3) Stem cuttings are another option. Cuttings should be taken in the spring or summer, and you need about six to eight inches of a stem that has come off the main branch. Cut it at the join with the main branch using a sharp tool. Ideally, cuttings should have three or four nodes on them to maximize your chances of success.
Remove all but the last two leaves, and then bury the ends of the cuttings in a mix of moist sand and potting soil so that they are about three inches deep. You can use rooting hormone to increase your chances of success and speed up the process if you like.
Cover the cutting with a clear plastic bag after misting the soil, and gently moisten if it dries out. Roots should start to form in less than eight weeks.
Repotting
You may sometimes need to repot your black diamond crape myrtle if you keep it in a container. If you have one of the large varieties, this is more likely as it will outgrow the container over the years. You don’t want the plant to end up root bound, so find a large container and fill it with well-draining, slightly alkaline soil.
You should water your black diamond crape myrtle before you take it out of its current pot. Give the water some time to soak into the soil and soften it. This reduces the chance of damaging the roots as you lift the plant out of its pot.
Position it in the new container, fill the remainder up with compost, and water gently to settle the soil around the roots. Most plants then prefer to be put in a shady place for a little while to recover from the shock of transplanting. Put your black diamond crape myrtle out of the full sun for a few hours and give it time to settle into the new container.
Once you are happy that it has acclimatized, move the container back to the full sun so your myrtle can keep enjoying the light!
F.A.Q.
There are a few things you might be wondering about your plant, so we’re going to cover a few of the frequently asked questions about black diamond crape myrtles.
Do I Need To Prune My Black Diamond Crape Myrtle?
You do not have to prune a black diamond crape myrtle; these trees will grow happily without being cut back. However, sometimes you will want to take off branches and improve the plant’s shape, and this should be done just as the dormancy period is ending, so around late winter/early spring.
You don’t want to take off new growth that starts when the tree wakes up, but you also don’t want to disturb its dormancy period. Pruning the tree while it is still asleep will cause it to wake up too early and this is damaging to its health.
You should avoid doing any heavy pruning from mid spring to late summer, but you can remove suckers from the base, dead or broken branches, or “water sprouts.” These are fast growing suckers put out from branches, and they will sap the energy from your tree.
You don’t need to prune your black diamond crape myrtle if it’s happy and healthy and you like its shape. There is a myth that pruning is necessary for the plant to flower, but this is simply not true.
If My Black Diamond Crape Myrtle Loses All Its Leaves, Has It Died?
If this has happened during the winter, the chances are that no, the plant has not died. It has simply gone dormant, which it needs to do every year. Don’t worry about it! You can leave your plant alone until the following spring, and it will be fine.
When the weather starts to warm up, check your plant over. You should start seeing signs of new growth, such as leaf buds and early leaves, around April or May. If you have a particularly cold year, it could be later than this.
If the plant does not grow new leaves when spring comes, it is possible that it has died. You should give it a few months before giving up, however; it may surprise you!
Why Is My Black Diamond Crape Myrtle’s Foliage Very Pale?
In spring, black diamond crape myrtle foliage does tend to be paler as new shoots form. It should darken as the year progresses, so don’t worry about this. However, if the plant continues to look pale, check it for pests and make sure you are feeding it properly.
