Ask the determined gardener

Many of my pines have died of disease; what are some alternative evergreens?

OSU Fact Sheet 7674 discusses pine wilt disease and lists many alternate selections. I would recommend something with a cold hardiness of at least Zn-6. California incense cedar (Calocedrus decurrens), American holly (Ilex opaca), Chinese juniper (Juniperus chinensis) are some recommendations.

When do I prune my blackberries?

Established plants produce new canes while the old canes are producing fruit. During the summer prune the new canes back to 3 to 3 1/2 feet. This will force it to create lateral canes creating more fruit. While tip pruning new canes remove the last year’s canes that have finished producing; cut these close to the crown of the vine. Prune lateral branches in late winter, February or March, to 12 inches in length. Also thin some canes to allow more air circulation and ease of harvest. A good system is to trellis canes that produced during the summer on one side of your structure and new canes on the opposite side. This allows easy identification of the growth stages.

My blue spruce trees are dying and have drooping needles.

Blue Spruce can suffer from two diseases: Cytospora Canker and Rhyzospharea Needle Cast. Trees infected with Cytospora Canker show scattered branch dieback mostly on the lower branches. Rhizosphaera Needle Cast shows needles on the lower branches turning purple or brown color. Prune branches 4 to 6 inches back from infection area. Both diseases can enter due to weakness or from winter pruning or stress. Prune only in dry weather. Rhyzosphaera Needle Cast can be treated with fungicide the last 2 weeks of May and again 4 to 6 weeks later. In general, this variety is not a good fit for Oklahoma weather and you may want to consider alternative selections.

How can I get rid of wasps under my deck?

Paper wasps can be eliminated with a standard aerosol insecticide “wasp spray” with fast knockdown and freezing components. For yellow jackets get professional help for large nests in wall voids or attics. To get rid of both: use protective clothing and cover the nests with an aerosol with a rapid knockdown insecticide. Control nests at night when wasps are sleeping. OSU Fact Sheet F-7305 has more complete instructions to control several wasp species. To maintain your own gardening and pest knowledge, acquire a binder to assemble and sort new information as you receive it. With this in hand you can quickly reference questions you have previously researched. Have a great gardening year.

You can obtain fact sheets on-line at Feel free to contact the OSU Extension Service at 405-713-1125 for more information.