Prune rosemary now before new growth begins

: When is the best time to prune my creeping rosemary? It has gotten very big.

A: You should be pruning now, just before new growth begins. A problem you could have is that the plants may be shading the interiors and if you prune too much, you will get to bare wood. It will look pretty ugly until new growth begins.

You can prune rosemary hard (to older wood with no green growth on it) and it will grow back provided the plant is in good health and was growing vigorously the previous year. I would delay this until you are sure most of the real cold winter temperatures have passed.

It may not bloom for awhile after pruning hard because you will get some fast new growth as the pruned top tries to catch up to the oversized roots. But once it gets some size back, it will begin to bloom profusely again.

Also, this spring fertilize it with some high-phosphorus fertilizer, like you would give to roses or fruit trees, and water it in deeply.

Q: I have a dozen pampas grass plants. They were purchased as the dwarf variety but about half of them are much larger than a dwarf. My gardener wants to cut them back. They still have plumes on them and add so much to my winter landscape. Are they supposed to be cut back? If so, when and how much?

A: Pampas grass is a clumping ornamental grass frequently grown for its ornamental seed heads that grow in plumes. There are several varieties, which come in different sizes and even color variations.

They do not have to be cut back each year. However, after a few years, dead grass will accumulate throughout the plant and may begin to look a bit ratty. If you are enjoying the seed heads and think the plant looks good, then don’t cut it back. Wait until it starts to become unsightly.

The usual method of pruning is to cut back the clump to about 2 feet in height. If the plant is growing vigorously and has been established for several years, you might be able to cut it to within a few inches of the ground and have it come back.

Like any clumping ornamental grass, pampas grass can be dug up and divided in the spring.

Q: My lawn has become infested with crabgrass. How and when do I treat it?

A: I don’t know who identified your crabgrass, but if it is crabgrass, it can usually be crowded out of a lawn by increasing the competitiveness of the turfgrass. You can do this by increasing the mowing height (if it is tall fescue) to 2 inches to 3 inches, making sure it has an irrigation system that has good coverage and improving the overall density of the lawn by fertilizing it on a regular basis. Crabgrass is a poor competitor with a dense lawn.

If it is Bermuda grass, the mowing height should be kept at less than 1 inch.

Crabgrass is an annual and if we don’t get low enough temperatures during the winter — in the low 20s — it may not be killed and will persist through the winter. In this case, you are faced with removing it on your hands and knees with a knife. There are chemicals you can use but they will usually damage the grass.

Pre-emergent control of crabgrass is done around the middle of February. These are chemicals applied to lawns and shrub areas to prevent the germination of new crabgrass plants. They can be obtained at your local nursery.

Q: How do you prune a blue palo verde? Are the multitude of small side branches removed? How about branches that point down? It does not look like normal pruning rules apply.

A: Be very careful when pruning blue palo verde. You must leave the trunk shaded to prevent sunscald. Once the sun damages the trunks, then borers and other pests will invade and cause the tree to die back.

Remove lower branches so they are high enough to walk under, but try to leave limbs on as low as possible. Let the upper limbs droop as much as possible without interfering with people’s activities.

Regarding sideshoots, I would leave on those that are smaller in diameter than a pencil, if the tree is relatively young. After the trunk shows signs of age, such as furrowing, darkening and the development of bark, then the trunk will be more protected from the sun.

Q: I want to move some plants from the front of my yard to the backyard. Can I do that now?

A: Yes, but the fall would have been a better time. If you are going to do it now, then do it right away.

Larger plants that have been in the ground for three or four years can be moved quite successfully.

Predig the hole that will be the transplant’s new home. Dig it deep to make sure you have drainage. Use the proper soil amendments and fertilizer for the backfill and mix it prior to moving the plant.

Remove the plant from the ground, being careful not to pull on the stems. Lift the plant only by the rootball. Take as much of the soil with the plant as possible. Carry the plant with the rootball to its new location. It is important that the soil ball containing the roots not break apart when the plant is moved.

Carefully lower the plant into its new hole trying to orient the plant in the same direction as it was in its old location. Backfill the planting hole with the amended soil and add water as soil is added to the hole. This will remove air pockets. Do not step on the soil amendment surrounding the plant. Make sure the plant is at the same depth as it was in the old location. It is important to get the plant out of its old hole and into its new hole as quickly as possible.

Prune the top of the plant, removing one third of the top growth. This is to compensate for losses to its root system in transplanting.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at extremehort@aol.com.