When transplanting a large plant several steps should be followed.

First, it is best to stimulate a tight root ball by root pruning the plants to be moved about a year before moving. This is accomplished by cutting a circle around the plant stem with a shovel to cut off roots that extend beyond this point. This radius is usually slightly smaller than half way to the drip line.

Second, it is best to move when the plant is dormant and not stressed. This would be in the spring and fall when the plant is still dormant but the soil is not frozen. Moving in the fall before the ground freezes is preferable if you don't have a problem with frost heaving. Sometimes winter freezing and thawing cycles can actually lift a transplanted plant out of the ground where the roots are then desiccated and the plant dies. For this reason, it is safer to transplant in the spring after the ground thaws in climates where frost heaving is a problem.

Third, take precautions to preserve the integrity of the root ball. Tie the ball together and support is so it doesn't fall apart. The very safest approach is to dig a trench up to 12 inches deep, around the dripline of the plant. Then undercut the plant to form a cone, removing the soil an inch or so at a time, moving all around the plant, until you begin to see that you are removing roots. If possible, then get a square of burlap under the plant. Tilt the plant to one side, put one edge of the burlap close to the center of the plant, wadded up so that only half of it is on the open side of the plant, then rock the plant the other way and pull the burlap through. Tie the corners of the burlap to each other across the plant. Tie the burlap tightly to keep the soil around the plant roots undisturbed. Then lift the plant by the burlap and the bottom, not by its stems.

Finally, pruning the top helps match the demands of the top to the capability of the roots after they are stressed by the move. People have been known to cut the top off wild rhododendrons before moving and the plants have come back with superior shape. This is drastic and not recommended for a plant you don't want to risk loosing. Rhododendrons and azaleas have dormant buds beneath the bark which sprout to form new growth after severe pruning, hence severe pruning which removes 1/3 to 1/2 of leaf area is quite common when transplanting.

The main problem you have with wild plants is that the root system is very simple. Transplanting is what makes a plants root system develop. Hence, the root pruning step is important unless you can take such a large ball you don't disturb the roots.

Here is a link that might be useful: How to grow azaleas

I have two Rhododendron plants that are at least 8 or 9 years old. They have never grown more than they were when I planted them. They bloom a little but just don't grow. They are planted in mostly shade. Should I transplant into more sun? If so can I do it now? I am really sick of them as they are. Thanks

It sounds like they are not happy. There are a number of reasons they may not be happy, but shade is not at the top of the list. If shade was the only problem, they would be tall and spindly. Here are some requirements to consider:

I. Variety: The rhododendron must be suitable for the climate where it is planted. Some varieties are too tender for harsh winters, too tender for very hot weather, too sensitive to droughts or wet conditions. Select the variety for the location. Different varieties grow different heights. Some are tall, over 6', and some are dwarf, barely 12", and many are in between. Unfortunately, most rhododendrons never stop getting taller, but their height is quoted for plants that are 10 years old and by that time most varieties have slowed down their growth considerably. But if you choose plants that are the right size to begin with, they are relatively maintenance free.

II. Soil Drainage: Because the fine roots of rhododendrons are easily blocked by fungi, excellent drainage is important. To test drainage, dig a hole 6 inches deep in the bed and fill it with water. If the water has not drained from the hole in an hour, install drainage tile to carry away excess water, or build raised beds. Moist well-drained soil is a must for most varieties. This sounds difficult, but it means to not let the soil dry out completely but don't get it too wet. Thoroughly water if necessary and then let it become almost dry. Most gardeners do this by planting in a well-drained area and mulching to hold the soil moisture in. Watering is seldom necessary except during long dry periods.

III. Acid Soil: Most varieties require an acidic soil (pH 4.5-6). Powdered sulfur is the best agent to acidify the soil. Holly-tone has this in it. Your plants will get chlorotic if the soil is not acidic enough.

IV. Fertilizing: When rhododendrons are not planted in ideal locations they may develop chlorosis. Chlorosis is yellowing of a leaf between dark green veins. It is caused by malnutrition that can be caused by a wide variety of conditions. They include alkalinity of the soil, potassium deficiency, calcium deficiency, iron deficiency, magnesium deficiency, nitrogen toxicity (usually caused by nitrate fertilizers) or other conditions that damage the roots such as root rot, severe cutting of the roots, root weevils or root death caused by extreme amounts of fertilizer. In any case, a combination of acidification with sulfur and iron supplements such as chelated iron or iron sulfate will usually treat this problem. Holly-tone contains these elements and 4-6-4 fertilizer. It is best applied in the spring prior to blooming to make sure the plant is healthy when forming next year's flower buds. If you missed applying it in the early spring, it can be applied up until mid summer. Rhododendrons do best when left alone in the right conditions. You don't need to use Holly-tone or any fertilizer unless the plant shows signs of malnutrition.

V. Shade: Some shade; some varieties like full sun to bloom but others suffer from too much sun. This is a trial and error thing unless you know the variety and can look it up. More sun stimulates flowering and but may trigger lace bug infestations. Prune off lower branches of shade trees so that you have "high shade" above your rhododendrons. This is ideal for a healthy rhododendron bed.

VI. Mulching: Rhododendrons do best when they have about a 2" to 3" layer of mulch to hold in moisture, prevent weeds, and keep the roots cool. Since most mulches are organic, they need to be topped off periodically, usually about every year or two. Do not make the mulch over 3" thick. Keep the mulch about 2" to 3" back from the trunk/stem of the plants to avoid bark split and rodent damage. Do not use peat moss as a mulch. It is a soil amendment to be used when preparing the soil in a bed and can cause severe problems when used as a mulch including dehydrating the soil and preventing moisture from reaching the soil. It also tends to blow around. It is best to mulch with a 2-inch layer of an airy organic material such as wood chips, ground bark, pine needles, pine bark or rotted oak leaves. A year-round mulch will also provide natural nutrients and will help keep the soil cool and moist.

VII. Protection: In choosing a location to plant rhododendrons, protection is very important. Protect from winter winds. This is especially true when the ground is frozen. Also protect from deer. I use deer netting in the winter and have a couple beds protected by deer fencing all year long.

VIII. Cultural Problems: Most problems are cultural. Some tender rhododendron & azalea varieties are not suitable for growing outside green houses. Cultivating rhododendrons must be avoided. They have shallow roots and the roots will be severely damaged by cultivating. Weed killer from weed & feed products is a definite problem also. Salt from sidewalks in the winter is a killer to rhododendrons. Soil near masonry such as foundations and walks is usually alkaline (not acidic) and a problem. Lawn fertilizer in the fall can set an azalea way back. Another problem is the roots of walnut trees. They emit a chemical that is toxic to rhododendrons and many other kinds of plants.

Here is a link that might be useful: How to grow rhododendrons and azaleas.

I would like to relocate 6 azaleas that were closely planted in the center of a circular driveway many years ago. Due to the restricted area that they are currently located I am sure their roots must be seriously intermingled. The previous owers of the property did not trim them for some time and are all about 6' tall. I believe I would have to trim the height just to access the roots, and assume I am going to have to use a backhoe/bobcat to just lift them. We live in the wilderness/swampy area south of New Orleans and all of the smaller old azaleas we have relocated so far are doing well. These will be relocated from their restrictive area to a space that will allow them to grow to their natural size. One neighbor removed an enormous azalea with a tractor and it lived for weeks with its badly damaged root ball exposed to the summer weather.
Any and all advice will be helpful.

The best thing to do is cut a slit between them now with a spade to cut the roots that are intermingled so it will be easier to transplant later. They have shallow roots so you only need to dig down about 6" to cut the roots. If done now they will form denser root balls that are easier to move.

I would also start cutting back the top so they will be easier to move.

It is best to never let the root ball dry out. First, it stresses the plant severely and will kill it. Second, it is very hard to hydrate the root ball once it drys out.

I have a poor rhodedendron that has lost it's root ball in transit; it has a couple of sad little roots and buds that haven't flowered. I have stood it in a pot with gravel at the bottom, a small amount of soil and loads of fir trimmings in the hope that I may be able to convince the roots to grow. Am I being too hopeful? Is it beyond salvation? Is there anything else I should be doing to provoke root growth instead?

Remove the buds. You want root growth, not top growth or flowers. Reduce the size of the top to match the size of the roots that are left.

Basically treat it like a cutting that you are trying to root. That means keep it in a moist environment, but not wet. Cut all of the leaves in half. Remove buds. Reduce the top to about 4 leaves. You should use a sterile medium such as is used to root cuttings.

Good Luck!

um - there really are only a couple of tiny tendrils left where the root ball should be, the leaves are looking really wilted now. the plant is about 80-90cm tall. should I just replace it?

Probably. It is best to plant in the fall. Summer is the worst time to plant or transplant.

Rhododendrons and azaleas have hair like roots. You need a good root ball to make sure you don't break off the fine hair like roots. The larger roots are just for structure, not nutrition and water.

Here is a link that might be useful: How to grow rhododendrons and azaleas.