Compost, Mulch or Bark – What’s Better for a Flower Garden? Ask an expert


We are well into fall, but there is still plenty to do – or just dream about in the garden. You may have questions. For answers, see Ask an Expert, an online question-and-answer tool from the Oregon State University Extension Service. OSU extension teachers and master gardeners answer questions within two working days, usually less. To ask a question, just go to the OSU extension website , enter it, and include the county where you live. Here are some questions asked by other gardeners. What is your?

Q: What is the best mulch over compost over bark for our existing healthy landscaped flower garden? When / why / how to use all or part of it? We applied high quality compost a year and a half ago when we started the flower garden. Nothing added since. – Washington County

A: Thank you for your question on the different mulches (these are all technically mulches) that you can put on your flower bed. They all have pros and cons so I will include a item of the state of Oregon, but skip to the part where it says “Choose a mulch” to see what is available.

Since you have already added compost, I suggest doing a soil test if you want to use it as a mulch, as the nutrients in the compost can last for a while.

If you’re looking to control weeds and conserve water, you probably want bark or wood chips. I love the arborist crisps that you can have for free on They are quite large but do not need to be replaced often. However, you must have a large area where they can be dumped.

Bark and wood chips can be purchased at garden stores and also last a long time. And if slugs are a problem for your flowers, I have been lucky with the hazelnut shells, although they are expensive to put on a very large area.

Of course, the shredded leaves are also a good mulch if you have a tree that is dropping leaves right now. They will decompose faster than wood products, but the tree will then provide you with a new batch next year. Here is more information.

Whatever you choose, mulching is a great way to help your plants stay weed free and well watered! – Rhonda Frick-Wight, OSU Extension Master Gardener

Q: I plan to build a creole house to grow food year round here in Port Orford. Do you have any ideas on how best to do this ie. Best film type, single or double layer shade cloth, etc. ? – County of Curry

A: here, here and here Here is some information on building hoop houses, bells, greenhouses, and things to consider when choosing building materials. – Samantha Clayburn, OSU Extension Master Gardener

Q: I am looking for a spotted shade tree for my west facing backyard. I came across the thornless locust (‘Sunburst’ or ‘Imperial’ specifically). But the articles or news that I find only mention the pests, mites, midges and other things that seem to attack these trees. Some suggest spraying trees regularly, such as with malathion. But I think it might harm the bees.

My question is, are these things really a problem for such a tree planted in a backyard, and if so, what would be the safe and proper way to deal with these things? I love the look of the tree, but if that comes with that hassle factor, then I’ll go for something else. – Yamhill County

A: Here are some pros and cons:

The thornless locust is a magnificent tree. It will grow quickly and provide the shade you are interested in. However, there are a few other things you should know.

They develop long pods that drop to the ground. These need to be picked up otherwise they will start new trees. Their rapid growth is due to their very efficient root system and will absorb moisture from the soil. If you have other plants or vegetables in the area, the tree may take up too much water, leaving other plants in need of more.

The leaves turn golden yellow in the fall and the pod contents are edible. They can develop cankers which are holes or growths that ooze sap. It attracts insects. Cankers are difficult to remove if you can.

They grow very tall – 40 to 50 feet tall and 30 to 40 feet wide. This may not be a problem for you, however. Pruning will help reduce the size, if desired. They do well in areas of car traffic, so they are tolerant of exhaust fumes, which makes them quite sturdy. The leaves are easily mowed in the grass around the tree. They also have a very strong wood so they are not prone to breaking branches in windstorms, not that a windstorm cannot break the branch, this just doesn’t happen as often as it does. with other more fragile trees.

The insect problems are bagworms, borers, mites, midges, but with organic sprays you can reduce populations if you have the bugs. A spray of horticultural oil will kill sprayed insect eggs in the fall and after petal fall. The flowers of the tree are extremely fragrant and attractive. They are creamy white and form long panicles hanging from the tree.

About 10 years ago, I simply threw some locust pods in the wooded area at the back of our house. Never done anything; didn’t even cover them. We have a nice stand of acacia trees, no problem I can see. But they germinate easily. – Sheryl Casteen, OSU Extension Master Gardener


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