Mild spring allows early prep for planting

KENNEWICK -- Go. Go. Go.


The very mild spring weather that we have experienced over the last month has plants and gardeners getting ready to go, but some recent cold nights may be putting the breaks on a bit.

I'm always wary of early warm spring weather, because weather has a way of changing very abruptly.

However, the tenuous forecast for the remainder of the month indicates daytime temperatures in the 60 degree range and nighttime lows above freezing. Based on this forecast, gardeners can get going.

The time to apply crabgrass preventer or re-emergent herbicide type materials is before crabgrass germinates. When crabgrass germinates is dependent upon the temperature of the top inch of soil. Germination occurs when the daytime and nighttime soil temperature reaches 55 to 60 degrees and stays there for about a week.

We often tell gardeners to wait until area forsythia is in bloom for several weeks before applying a preventer material. However, this bright yellow flowering shrub is what's called a phenological indicator. It blooms when soil temperatures are approaching that 60 degree range. An inexpensive soil thermometer is a more accurate way to determine if it's "time."

So why do we dither so much over when it's time to apply "crabgrass preventers" every spring?

University research indicates that crabgrass may start germinating when the soil warms up to 60 degrees, but it can continue to germinate over the next 12 weeks. If you apply your preventer material too early, it may dissipate before all the crabgrass germinates later in the summer.

Forsythia also is an indicator that it's time to prune your roses.

Local Tri-City Rosarians recommend pruning your roses when Forsythia is in bloom. Now is the time.

As you prune, you may find that last December's severe cold spell caused some injury to your roses. Prune canes back to where you find white centers. Remove portions of canes where the centers are brown, tan or beige.

It's warming up fast, so if you haven't planted your early cool season crops, you'd better get going. Gardeners often like to plant their peas on St. Patrick's Day. Peas will germinate as soon as the daytime temperature reaches 45 degrees, but grow best when temperatures are between 50 and 60 degrees.

You also should plant peas, lettuce and cool season spinach. Also, get ready to plant your broccoli, cabbage, cauliflower, carrots and beets.

Now also is the time to cut back your ornamental grasses that have died back to the ground over the winter.

Cut the grasses back to about 4 to 6 inches from the ground. Some of the cool season grasses already have started to grow, so be careful not to cut back into new green growth. Start by tying all the stems in the clump together using rope or a bungee cord.

Use a hedge trimmer or small chain saw to cut across a clump of tough-stemmed grasses. Soft or fine stemmed grasses can be cut with a serrated knife or hand sickle.

So for now it's go, go, go, unless it snows.

* Marianne C. Ophardt is a horticulturist for the Washington State University Benton County Extension Office