The Crepe Myrtle is one of the most planted trees in the US; originating in China is it now grown throughout the world. The trees vary in size, from small shrubs to large decorated trees. Flowers on them can range from white to magenta and purple. Killing them can be quite difficult, you should wait until the temperatures are high for several days then cut them off ground level and drill holes in the remaining trunks. Fill these holes with 100 per cent roundup and this should eradicate the root system, keeping any roots you might have missed from sprouting at a later date. Wait several weeks and then get the roots out as best you can. Be aware that while roundup directly applied to the stump will kill a myrtle tree the roots might continue to shoot. The only way to be sure you kill the tree is by removing the stump completely and digging out all the roots. Another approach is to get a bottle of glyphosate systemic herbicide and some paintbrushes that you can throw away afterward. Try to trim some of the stump and paint the new area with herbicide quickly. When a new root sprouts up either cut up and paint it or try to dig it out. After some time the roots should starve and die. Be careful with herbicide and don’t get any on the ground if you can help it because this might contaminate the soil.