On the western side of Washington state, I have found some native trees that are very good for bees. I've read the other suggestions so I won't repeat them. The hawthorn trees are covered with bees. And the Cascara seems to bloom for a long time. All I hear is a loud buzzing every time I walk past either of these trees. And if you want to really help your bees in late summer plant wild marjoram. It starts to bloom in July and last at least 2 months or more, when there are fewer things in bloom. The bees are just covered on the marjoram every day. The plant is also drought resistant. We use the leaves to add to our eggs in the morning. It will spread profusely by seed. So, if you plant it be sure it's someplace appropriate. We have a few plants growing in our stone driveway. If you have a place to let fireweed grow, that is something we notice bees love. We let our kale go to seed and so we have volunteer kale coming up several places. When it flowers the bees are on it every day. The other one bee’s love that is prolific and spreads by seed if wild mustard. Bees use cottonwood trees for propolis so don't cut them down. I've heard a number of people saying how cottonwood isn't worth anything. The whole population needs re-educated that most all trees have benefits for our creatures of Mother Nature. Like dandelions. I purposely try to cultivate them in my field along with clover. I strongly believe diversity is so important for honeybees. We grow different herbs and flowers. Some of these things are small suppliers but the bees use pollen from many sources to make bee bread for food. We have an orchard so of course they gravitate to the blossoms of the different fruit trees. They love raspberries. And like I saw what one person mentioned already that wild blackberries are the biggest nectar source of all for most of our area. Something you will learn about is the mite problem that have killed so many hives. Oxalic Acid is one of the organic methods that I have found to be safe for the bees. It does not leave residue in the honeycomb like others. I got a wild swarm in the spring and had a good season with honey production. I tested my bees in late December with one treatment of Oxalic Acid fumigation. I put a white poster board that I slid in the bottom board through the front opening and then treated the hive. The treatment last for 3 days. I pulled the poster board out and counted how many dead mites had dropped onto the white poster. I was shocked at how many mites there were. I continued treating until I saw no more mites. If I had not done that, I would suspect that my hive would have failed and died come spring. If you are going to get bees, I would not buy a package from the commercial source. There are always swarms in May and June. Most likely the swarms are bees that made it through the year and are accustomed to the weather in your area. If you have trouble finding one yourself, call the different local beekeepers and tell them you will pay for them to catch a swarm for you. I wish you a lot of fun and happiness with your honeybee adventures.