Rosettes in Your Rosaceae?

Most orchards have weed growth under the trees in the so-called "weed-free" strip at this time of year. Look closely to see the many different kinds of weeds there, including annuals and perennials, grasses and broadleaves.

Already some of them are in bloom, and others will bloom by early summer. Many of these early bloomers are winter annuals, which are particularly adapted to the cycle of tree fruit production. These winter annuals germinated from seed late last summer or fall, when the rains returned. They grew in a dense, flattened form known as a rosette and stored enough energy last fall to overwinter and be ready to bloom early.

Winter annuals in orchards commonly include:

• Canada fleabane
• Common peppergrass (which is not a grass!)
• Common chickweed
• Thyme-leaved sandwort
• Mustards (wormseed mustard, common peppergrass, stinkweed or pennycress, shepherd's purse)
• Corn gromwell
• Henbit

Some biennial and perennial weeds may also establish in the fall. Dandelion, plantain, docks, buttercups, thistles, sheep sorrel, common mallow, creeping Charlie, and goldenrod that are starting for seed are in rosettes.

Canada Fleabane rosette

What should a grower do? Winter annuals are more difficult to control once the flower stalks have bolted. Delaying the spring burndown will make it less effective it will be - so be prepared to get out there earlier ie. keep prunings chopped or cleaned up, get your weed sprayer ready now.

Are early spring weeds really a problem? Definitely. The critical weed-free period for apples is in early spring - from budbreak until about 30 days after bloom. If trees are kept weed-free during this time, no yield reduction will result. Weeds growing after the critical weed-free period may cause other problems eg. hampering harvest, or shading lower fruit, but have little yield effect.

Think about the activities of your trees during this time eg. blooming, setting seed, dividing cells in the fruit, as well as putting on terminal growth and growing new roots. It makes sense to remove weed competition during this critical time.

How large an area needs to be weed-free? The weed-free strip needs to extend past the drip line of the tree. The most active tree roots are in this area, collecting nutrients and moisture. If weeds are allowed to grow, they always win the battle and your trees lose.

By the way, you likely already know that all tree fruit are in the Rosaceae family - in case you are wondering about my title.

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