We took out a tree and now finding our raised garden with feeder roots. The roots are definitely dead and I'm wondering is it necessary to dig out all the roots or just let them decompose?
Letting them decompose will be the best course of action.
Adding beneficial garden microbes will help, but specializing with fungi, such as Stropharia rugosoannulata and Clitocybe nuda will make quick work of the roots! In fact, adding any wood eating mushroom to the area will get rid of the roots within a season, leaving you with nutrient rich soil!
Here are some articles that will help:
https://www.gardeningknowhow.com/edible/vegetables/mushrooms/harvest-mushroom-spores.htm
https://www.gardeningknowhow.com/edible/vegetables/mushrooms/grow-mushrooms.htm
https://www.gardeningknowhow.com/edible/vegetables/mushrooms/grow-oyster-mushrooms.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/mushroom-compost.htm
https://www.gardeningknowhow.com/edible/vegetables/mushrooms/propagating-mushroom-ends.htm
https://www.gardeningknowhow.com/edible/vegetables/mushrooms/growing-wine-cap-mushrooms.htm
My trees have roots that are growing above the ground and the lawn and grass is skimpy. What should I do?
Trees benefit from a layer of mulch under the tree out to the dripline. That may cover the roots and the skimpy grass. This article also suggests planting a ground cover like monkey grass instead of the grass.
https://www.gardeningknowhow.com/ornamental/trees/tgen/exposed-tree-roots.htm
Last year we flatted our lawn and had a retaining sleeper wall built. Unfortunately, part of the lawn is very wet and the grass hasn’t grown very well as a result. We’re hoping that by planting things above we may be able to absorb some of the water that’s sitting on the grass. We’re therefore looking for ideas of what to plant above. Any help would be gratefully received. Thanks in advance.
Planting above probably won't solve the issue, but planting water tolerant plants, directly, in the wet area might help! Not only will they help to absorb water, but they will thrive in the wet environment.
This article will help:
https://www.gardeningknowhow.com/ornamental/water-plants/wgen/water-tolerant-plants.htm
Alternatively, these articles will help you to solve your drainage iddues in other ways:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/what-is-a-french-drain.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/yard-drainage-problems.htm
Usually it is expressed with soil temperature. For convenience, you can take the temperature in early morning. The best temperature for growing peas is between 60 and 75 degrees F., as they are a warm season vegetable.
http://www.gardening.cornell.edu/homegardening/scene9697.html
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/determining-soil-temperature.htm
Hi - I have this one area that floods in my garden - what can I do to utilize this area?
Here are a few articles that should help:
https://www.gardeningknowhow.com/ornamental/water-plants/wgen/water-tolerant-plants.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/wet-soil-trees.htm
https://www.gardeningknowhow.com/special/spaces/rain-garden-design.htm
It is very difficult to say with limited information.
Excessive rainfall can cause root rot, and suffocation depending on exact species. Some are more tolerant than others.
It is very possible that the rainfall has killed off your plants, though. If this is normal for your area, then you may consider plants that tolerate wet soils.
This article will help:
https://www.gardeningknowhow.com/ornamental/water-plants/wgen/water-tolerant-plants.htm
Would like so advice on how I can remove/ get rid of this water that seems to be rising from underneath the turf?
These articles will help you with yard drainage:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/yard-drainage-problems.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/wet-soil-trees.htm