Caring for a Black Diamond Crape Myrtle

Introduction

If you’re looking for a stunning plant that will grow in all sorts of climates and circumstances, the black diamond crape myrtle is perfect for you. They come in a variety of different colors, and have rich, burgundy foliage to brighten up your yard when they aren’t in flower.

These plants have a nice, long flowering season so they are an excellent way to bring color to any garden, and you can get both big and little varieties, making them a flexible plant that will fit into almost any space.

You can grow black diamond crape myrtles in pots or directly in the ground. They like a good amount of sun and don’t like extreme cold, but will cope if the temperature dips a bit. You need to provide plenty of food and water for them throughout the spring and summer.

Indoor vs Outdoor Growing

These plants are grown outdoors, partly because they need a dormancy period throughout the winter, and without this, they will often get sick and die. Most people plant them directly into the ground and never bring them into their homes. They are not houseplants.

If you live in a particularly cold environment, however, you might sometimes want to bring the plant in to stop it from getting frozen in very cold weather. That is why many people in cooler environments grow these plants in containers – because they can move them inside when necessary.

Do be aware that plants in containers are often more susceptible to frosts than those planted in the ground, so if you can’t bring the plant inside and your winters are cold, it’s better to plant them in the ground.

These plants should only ever be brought into a garage, shed, or unheated porch. The warmer temperatures inside the home might pull the plant out of its dormancy period early, and this isn’t very good for the plant.

When the weather starts to warm up, you need to move the black diamond crape myrtle back outside, but you may wish to harden it off first. To do this, place the plant outside during the day, when temperatures are cool but not freezing, and carry it in at night. This will help to keep the plant safe from hard freezes, but encourage it to start adjusting to the cold.

Best Location For Your Black Diamond Crape Myrtle

As mentioned, these plants prefer to be grown outside, and as long as you live in the USDA zones 7, 8, or 9, you can grow them outside throughout the year, without worrying about the temperature dropping (or possibly getting climbing too much).

When choosing the perfect location in your yard for your plant, take a bit of time to look at the position of the sun and where it falls in your garden for the longest periods of time. These plants like to be grown in full sun and need about six or more hours of direct light most days if they are going to grow well.

If you want to make a hedge out of these beautiful plants, you can do so by planting them in a long row. This will be one of the prettiest hedges on the block, especially when in flower! Some kinds can grow to around fifteen feet high, so you don’t need to worry about privacy with these. Lots of sun will help to keep them healthy.

If you live in quite a cold zone, you may want to plant your black diamond crape myrtle closer to the house. The shelter of a building often helps to keep the ground warmer, and some heat will radiate away from the house and may save your plant from frosts.

Other plants may help to provide shelter too, though often these plants get too big to get much benefit from other plants.

You can try putting wool or other natural insulating fabrics around the soil to keep the roots a little warmer and reduce the chance of freezing, but if you live in a cold place, you’ll need to bring these plants inside to help them survive the winter.

Soil For A Black Diamond Crape Myrtle

So, we’ve covered where to plant them – what about what to plant them in? You need to think about what you’re going to be putting their roots into and how well they will cope with it. A plant that doesn’t have good soil will not grow well at all.

You might want to test the pH value of your soil to start with, and check out whether you are dealing with sand or clay. Black diamond crape myrtles like somewhat alkaline soils, or at least neutral, and won’t handle acidic soil well.

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They don’t like clay, either, so if you have a clay-heavy garden, you might want to plant your black diamond crape myrtle in a container, rather than in the ground. They need good drainage, and in clay soils, too much water will sit around their roots and cause rotting.

Watering Your Black Diamond Crape Myrtle

As we mentioned, these plants like to be in well-draining soils and don’t want to be too wet all the time, or they will rot under the ground. Fortunately, once your plant has got a good root network spread under the soil, you probably won’t need to water it very often, even in the summer. It will collect moisture for itself.

When your plant is young, however, you do need to water it, and often. Many growers recommend watering it both before and during the planting process, and then a lot afterward. Some even suggest building a dike of soil around the edge of the plant’s roots to encourage water to flow toward the plant.

Deep watering is key when the plant is young. This means saturating the soil thoroughly so that the moisture really sinks in, and then leaving the surface to dry out a bit. This sort of behavior encourages the plant to put down deep roots, which will help it to find water when it is an adult. Water it deeply once or twice a week, rather than shallowly every day.

You can also add mulch to the surface of the soil, and this will help to trap moisture underneath. Cut grass, leaf litter, or straw will all work to help keep the moisture in the soil, where your plant can reach it.

Take good care not to let a young black diamond crape myrtle get too dry, especially in its first year or two. An established plant should be able to get enough to drink for itself in all but the driest summers, so you won’t need to water adult plants that are growing in the ground – although plants in containers will still need attending to in dry spells.

Humidity For Your Black Diamond Crape Myrtle

Excessive humidity isn’t very good for your black diamond crape myrtle. While the plant will tolerate a bit of humid air, lots of it for several nights running can lead to powdery mildew appearing on the plant’s leaves.

You may notice a white-ish fuzz covering your plant’s pretty foliage, and wonder what this is caused by. Unfortunately, it’s a kind of mold that results from the plant being damp overnight. It is very common and can be quite difficult to deal with. It won’t kill your plant, but it may stunt its growth, and it is not very pretty.

You can’t do much to treat powdery mildew, unless you can increase the airflow around your plant. Moving air will help to dry the leaves and prevent the mold from forming. However, if you can’t do anything about the humidity, don’t worry – because the mildew will clear up on its own when the sun next shines, especially if your myrtle is in a sunny spot.

Some people suggest using milk mixed with water to treat powdery mildew, as a protein in the milk kills the mold. You can also buy commercial sprays that should help.

Alternatively, look for a species of crape myrtle that is resistant to this sort of disease, and try to dig it in somewhere that has good air circulation and few other damp-inducing plants nearby.

Fertilizing Your Black Diamond Crape Myrtle

If you don’t feed your plant, you will probably see far fewer flowers than if you give it a balanced food throughout its growth season. You should keep an eye on your black diamond crape myrtle and use its behavior to tell you when to use fertilizer.

For example, when the plant begins to grow new leaves in the spring, you should begin fertilizing it for the year. Nitrogen is an important nutrient at this time, and will encourage lots of good leaf growth, so choose a high-nitrogen fertilizer.

There are different fertilizing methods, so you’ll need to find one that works for you. Many people like to fertilize throughout the plant’s whole growing season, watering a diluted fertilizer into the soil around the plant. You can either use a liquid fertilizer or a slow release fertilizer – either should work fine, but make sure you follow the manufacturer’s instructions.

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Always water your plant well when fertilizing, to reduce the chance of root burn. If you notice salt building up on the soil’s surface, give the plant a very thorough soak to help this wash into the ground and prevent it from damaging the roots.

You will probably want to stop fertilizing for the winter, and start again when the plant starts growing (usually around March). This stops too much fertilizer from building up in the soil. As well as root burn, over-feeding can cause your plant to produce lots of leaves but few flowers, which isn’t very attractive.

A black diamond crape myrtle that isn’t fed properly will probably keep growing, but it may be slow and produce only small amounts of flowers. A plant that has access to all the fertilizer it needs should grow fast and be laden with blossoms. On the whole, it’s better to under-fertilize than to add too much, but both should be avoided where possible.

Toxicity

For a pet owner, any garden plant needs to be assessed for potential toxicity, but the black diamond crape myrtle should pass with no problem. These are not poisonous to people or pets, so you don’t need to worry if your kids or dogs take an interest in them.

You still should discourage them from eating the black diamond crape myrtle, but there should be no ill effects if they do consume parts of the plant – so don’t worry too much. These plants are safe to grow in your garden.

Propagation

It isn’t very common for people to try and propagate black diamond crape myrtles, but it can be done. If you don’t want to buy an established plant from a local nursery, let’s find out how to propagate!

You can, of course, propagate these plants by collecting up the seeds once the season’s flowers are over. Wait for your plant to form its seedpods at the end of the season. The pods can be picked off in the fall, and then dried indoors.

When the seeds are dry, you can take them out of their pods and then simply plant them in containers with rich compost. You do not need to bury them deeply; a slight press will do.

Cover the container with sphagnum moss, water it lightly, and wrap a plastic bag around it to keep the environment humid. Put it in a safe place and check on it regularly. Hopefully, the seeds will germinate in about three weeks, and then you can remove the plastic bag.

Keep watering the seedlings lightly and wait for them to grow. When they are a few inches high, you can remove them and replant them in a larger container. Don’t put them into the ground until they are strong plants, as they may struggle to compete with other plants.

If you don’t want to plant the seeds, consider taking a stem cutting from your established black diamond crape myrtle. This is very easy to do. In the spring, you should select a strong, healthy stem with several nodes on it, and cut it at about eight inches long. Check the stem looks good, and then dip the end in rooting hormone.

Remove most of the leaves and prepare a container with compost and some sand. Bury the cutting in this container, water it, and then again put it in a clear plastic bag to keep the moisture in. Check on the cutting frequently and throw it away if it turns moldy. If you are successful, you should start seeing roots within a couple of months.

Let the plant get strong before you try and transfer it to a larger container or plant it in the garden.

Repotting

Black diamond crape myrtles that are in the ground obviously won’t need repotting, but if you keep yours in a container, you will have to change the pot every few years, especially if you have one of the bigger varieties.

These plants aren’t very keen on being root bound, so repotting them when they start to get crowded is important. A black diamond crape myrtle that has outgrown its container will dry out quite fast.

You should begin by watering your plant thoroughly, and then preparing a larger pot with fresh soil (preferably slightly alkaline). You can also add a layer of gravel to the bottom for drainage if you like.

Next, lift the black diamond crape myrtle out of its current pot and gently place it in the new one before pouring more compost in on top of it. Water the plant gently and you’re all done! Your myrtle may suffer from a little shock and might shed a few leaves, but you shouldn’t notice any other major problems.

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If you grow your black diamond crape myrtles in the ground, you may sometimes wish to add a bit of compost to them to help them grow. This can be done in addition to fertilizer (but you should reduce the amount of fertilizer you give the plant for a while).

To do this, simply spread some fresh compost around the plant’s stem. Over time, the rain will wash the compost and nutrients into the soil and to your plant’s roots, giving it a good feed.

F.A.Q.

What are some of the other things you might wish to know about your black diamond crape myrtle? We are going to cover a few FAQs here.

Should I Water My Black Diamond Crape Myrtle In The Winter?

This will depend a bit on your plant and the climate where you live, but you may not need to water it much in the winter, if at all. An established plant may have no need for extra water, especially if you live in fairly wet conditions.

Dormant plants don’t tend to drink very much, so you should only water your black diamond crape myrtle during the winter if the weather has been exceptionally dry. Do not soak the ground, but add a bit of water and wait for it to seep in.

This will ensure there is some moisture available to the roots without too much risk of causing the roots to rot. If the drainage for your plant isn’t good, be careful doing this, because the water may not evaporate or run off much in cold conditions.

Remember, you don’t need to fertilize during the winter either. In most cases, you won’t need to give your black diamond crape myrtle any attention at all while it’s dormant. You can leave it alone until it begins to grow again the following spring.

You shouldn’t worry if your plant looks dead during the winter either. While dormant, black diamond crape myrtles can look as though they have died. Even if your plant has lost all its leaves, it is probably just fine. In the spring, you should see new growth, and your plant will bounce back to its beautiful self when the warm weather comes.

Why Isn’t My Black Diamond Crape Myrtle Flowering?

These plants are usually prolific bearers of flowers, so if your plant is not producing many blossoms, you should investigate. It may be that the plant has had too much fertilizer (if it’s producing a lot of new leaves) or that it is too hungry to produce flowers.

Lack of flowers can also be caused by powdery mildew. Treat your plant with a milk solution and avoid watering it to try and reduce the humidity levels for a while. There isn’t much you can do to stop powdery mildew, however; you usually just need to wait for it to clear up on its own.

In the long term, choosing plants that are resistant to powdery mildew is a good idea. Some species have been bred to cope better with humid conditions and provide a less suitable home for this kind of fungus, and these are a better option for your garden.

What Kinds Of Pests Attack Black Diamond Crape Myrtles?

Fortunately, not too many kinds of pests attack this plant, which is another great reason to grow them. You may see crape myrtle aphids, however, which are specialized to only eat myrtle trees and can damage the foliage and make the plant sick.

If you see yellow spots or deformed younger leaves, your plant may be battling with these kinds of insects. The best way to get rid of an infestation is to introduce a natural predator, such as ladybugs, parasitic wasps, lacewings, etc. Ladybugs and their larvae can be purchased as a form of pest control.

Put the insects on your plant and they should take care of the aphid issue pretty quickly. They will then go and attend to other insect problems in your garden.

You can also spray aphids off your black diamond crape myrtle using a strong jet of water, but this needs to be done frequently, and could put your plant at greater risk of powdery mildew. Insecticides are rarely effective against aphids.