March 2010

This 2009-2010 winter season has reintroduced Tulsans to winter as the bitter season, with the coldest, snowiest, gloomiest spell in a long while. And as March begins, it seems determined to stay. But Tulsa gardeners know full well that we can go from the dead of winter to high summer with barely a pause for spring, so it is time to prepare. In the Linnaeus Teaching Gardens the quiet, cold and gloomy days will give way to warmth and sun and an army of volunteers clearing up the ravages of winter. The Garden will be magically transformed by one of these major cleanup days, and then the quieter days of careful clipping and shaping will take place as the weather allows.

At some point big trucks will pull up and begin unloading this year’s gift of the newest and most exciting plants, sent to us by our industry partners, and the army of volunteers will again swarm over the Garden to get the new plants into the ground.

So what has to happen during March? Just about everything!

Don’t be discouraged if your garden isn’t as quick to start up as it was last year. Looking at notes jotted down from March 2009, it appears that perennial growth this year is about two weeks behind last year’s. In addition to the prolonged and deep cold, extended snow cover has kept soil temperatures cooler.

Turf

Cool season weeds are just throbbing to spring up and grow. Before then start your springtime regimen on Bermuda lawns.

• Cut the grassy hay back to 1-1 1/2” in height, rake and remove debris.
• Vericut or aerify if needed, removing debris.
• Hold off on pre-emergent application until mid- late April when the soil temperature is 56-58 degrees. Applying earlier will require a second application to control the later germinating weeds and crabgrass.
• Control henbit by keeping it cut too short to flower and set seed. It is an annual, so this will greatly reduce the amount you will have next year.
• Be wary of applying broad-leafed weed killers at this time as desirable plants are very susceptible to damage in the spring. A better time to apply will be in late October or November.
• Deadleaf Heuchera varieties; reset plants if they need to be rejuvenated. Fertilize with organic fertilizer at this time.

Woody Plants

• Complete any early spring pruning that was not completed last month.
• Spray azalea leaves with horticultural oil for control of lace bug and thrips. (Do this before they bloom.)
• Trim azaleas after flowers start to fade and apply horticultural oil again after pruning. If needed, you can do a light pruning on later blooming plants. Do NOT prune hollies or old varieties of hydrangeas now. If you are not sure of when to prune, use the Two Month Rule: prune within 2 months after the plant finishes blooming. That will give time for the wood to mature and produce blossoms.
• Clean up shrub beds, removing litter, and refreshing mulch.

Herbaceous Plants

• Clear fallen leaves from evergreen perennials.
• Pull back the protective mulch from the crowns of any perennial showing new growth but keep that protection close in case the temperature drops to 25 degrees or lower.
• February, March and April are important months to spray horticultural oil on perennials that are beginning to emerge from dormancy. This helps deter aphids and spider mites hiding out in the folds of the new leaves. DO NOT SPRAY HAIRY OR GRAY PLANTS such as Stachys, lamb’s ears or the gray-leaved dianthus. Also do not spray those early blooming perennials that have already set buds or are getting ready to bloom such as Phlox subulata, creeping phlox.
• Plant perennials this month, dormant, bare root or container. Bare root perennials respond best while weather is still cool.
• Divide summer and fall blooming perennials this month. Pot up some divisions for the SpringFest LG Plant Sale.
• As later blooming bulbs emerge, fertilize. This pertains to bulbs that are permanently left in the landscape, not to the bulbs replanted every year.
• To control iris borer, clean up and destroy old leaves before new leaves begin to emerge from iris rhizomes.
• Remove dead foliage from hostas and daylilies. It is better to do this in the fall after a killing freeze but be sure to remove it now. Aphids are notorious for hiding in the daylilies. Hosta can have slug and snail problems; removing dead leaves will take their hiding places away.
• Continue removing cool season weeds, henbit and chickweed.
• Pull up annuals from last year and pansies that didn’t make it through the winter. If you did not fertilize pansies do so now. They are heavy feeders.
• Cut back Miscanthus and Pennisetum grasses before new growth gets too tall.
• This year, with all the ice and snow, Carex foliage may have been damaged. Cut it back to couple of inches. (Carex glauca, C. morrowii and other Carex)
• Cut Imperata cylindrica ‘Red Baron’ to the ground.
• Acorus grass, especially the dwarf variety, will need cutting back. Shear it back to ground level. Apply fertilizer at the same time.
• Mow Liriope to 3” or hand cut.
• Shear Nepeta to basal foliage.
• If Salvia ‘May Night’ foliage is tattered from winter ice, cut it back to basal foliage.
• Deadleaf Heuchera varieties; reset plants if they need to be rejuvenated. Fertilize with organic fertilizer at this time.
• Deadleaf Epimedium varieties now before flowers start. If foliage looks good, there is no need to remove it. Fertilize it at this time.
• Prune all last year’s bloom stems off at this time. This includes Asters, Achillea, Astilbe, Phlox, Peonies, Monarda, Lilliums, Eupatoriums, Amsonia, Rudbeckia, Anemone, Asclepias, Companulas, Centranthus, Coreopsis, Echinacea, tall Sedums, and Solidago. Cut all stems down to within an inch from the ground. (The removal of old bloom stems is best done in the fall.) After working with these plants, fertilize with organic fertilizer. Remove damaged leaves.
• Deadleaf Pentstemon ‘Husker Red’ and other P. digitalis. Remove the bloom stems too. Apply organic fertilizer now.
• Towards the end of the month check the stems of Hibiscus ‘Cranberry Punch’. If they are starting to sprout from the ground, remove the old stems. Fertilize it at this time.

General

• The dry weather of February has left the soil in prime condition for working up new beds. Work up new beds deeply, a full 10 inches if possible, working in amendments such as mushroom compost as needed. Top dress existing beds with compost and cultivate as appropriate.

Vegetables

As soon as the soil has thawed enough and has dried out its’ winter sogginess, begin working up new beds. Be sure to work deeply, working in all amendments and organic matter thoroughly. Top dress existing beds with compost and cultivate as appropriate.

By St. Patrick’s Day, March 17, be ready to get your early crops in. Those would be potatoes, peas, favas, lettuces, cilantro, chervil, and spring onions, among others. Do not rush the warm season plants. Instead, work on producing thriving compact transplants. As low as the light levels have been this year, grow lights will help produce better plants. Do not be tempted to move these heat lovers outdoors too early. They will either stall or die unless you put in tremendous effort to thwart the season.

By Anne Pinc and Betsy Mickey