Answer: When plants consistently fail to root into the native soil and instead the roots are staying in the original potting mix, it can be very difficult to keep them hydrated because the potting mix tends to dry out very quickly. There are several things you can do to try to encourage the plants to root better.
One is to make sure you are not purchasing/planting severely potbound plants with roots tightly encircling inside the container. These roots will continue to circle and never grow outward if left alone. If a plant has encircling roots, the roots need to be cut at planting time and/or untwisted and teased into an outward direction to encourage them to spread out. Plant them in a generously wide planting hole so the roots are not crowded, and set the plant no deeper than it grew in the pot.
The next thing is to check that the soil in the planting area has been loosened over a wide area to encourage the roots to grow and that the native soil is well suited to the type of plant you are placing there. Some basic soil tests will help you determine the fertility levels, pH and general structure. Chamaecyparis in general prefer a slightly acid, fertile, organic, evenly moist yet well drained soil. Clay based soil for instance may need to be improved with ample amounts of organic matter such as compost plus some sand to help keep it loose and aerated so the roots can spread through it easily.
Next, roots will not grow into dry soil. Water well at planting to eliminate air pockets. Then water slowly and deeply as needed to keep the soil evenly moist but not sopping wet -- do this throughout the growing season and through the fall until the ground freezes.
You need to water often enough and deep enough so that both the surrounding soil and the original root ball are kept moist, but not sopping wet. Sometimes they drain at different rates. Overwatering can kill them just as underwatering can kill them. Test with your finger to see if and when you need to water. After watering, wait a few hours and then dig down to check and see how far the water has gone, sometimes it is surprising. This will help you know how much you need to apply at a time and also how often. You may need to water the potting mix more often than the surrounding soil.
Next, use several inches of organic mulch over the root zones (do not place it up against the trunk or stems) year round. This will help keep the soil evenly moist and cool and also keep down weeds.
This particular plant would do better in morning sun or in sun all day than in just the hot afternoon sun. This is particularly true if they are being used as foundation plants. For a planting on the west side of a building, a better evergreen choice might be the junipers, there are many low growing forms and they are available in different foliage colors and textures as well. Junipers would also tend to do better if the site is windy.
I hope this helps you trouble shoot. Your county extension may also have suggestions and should be able to help you with testing your soil and interpreting the results. I hope you get something growing well there soon.
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