Strangely, both our irises and rhododendrons did not flower this year. Any suggestions?
Since these are two very different plants that did not bloom, I suspect that you have an issue with phosphorus in your soil. Plants need phosphorus to bloom. Here is more information on that:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/phosphorus-plant-growth.htm
Have your soil tested to determine what is causing the phosphorus deficiency. You can also add bone meal (https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/bone-meal-fertilizer.htm) to the soil to add phosphorus.
Our rhododendron didn't bloom last spring. It was planted a year ago. Could it be that our soil is not acidic enough or that the plant is too young?
There are many reasons a plant may not bloom. The most common is that the plant is not getting enough sunlight. While rhododendron like shade, if they are too far back in the shade, they may not have enough light to bloom.
Another reason can be a lack of nutrients in the soil. Particularly phosphorous. Try adding a little bone meal to the plant and also have your soil tested at the local extension service to see if it is lacking any other nutrients.
Are rhododendrons poisonous to pets and children?
Although it has a low toxicity, it is best to treat all Rhododendrons as poisonous and keep out of reach of children and pets. Rhododendrons are toxic to many domestic animals, including dogs. Do not to allow your dog to remain unsupervised around these plants. They have potentially toxic leaves and flowers and even the honey from their flowers can be poisonous. While human fatalities from eating these plants are rare, victims who consume a lot suffer from nausea, vomiting, abdominal upset, and low blood pressure.
Why are the leaves on my rhododendrons turning yellow?
There are several things that can cause this. This article will help you pinpoint which cause could be affecting your plant:
https://www.gardeningknowhow.com/plant-problems/environmental/plant-leaves-turn-yellow.htm
How do you get rid of root weevils in the rhododendrons?
This article will help you:
http://cru.cahe.wsu.edu/CEPublications/eb0970e/eb0970e.pdf
Is it possible to start a new tree from a branch or other places from an existing tree?
This article should help with that: https://www.gardeningknowhow.com/ornamental/trees/tgen/how-to-root-cuttings-from-various-shrubs-bushes-and-trees.htm
Huge rose-colored blooms now. Plant is about 8 feet tall and must be 15 or 20 years old. What is the best method for pruning this back down to 5 or 6 feet? All at once or over 3 years?
Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/shrubs/rhododendron/pruning-rhododendrons.htm