March is one of those in-between months in the garden.
What can I plant in the vegetable garden right now?
It really is getting late to plant any more cool-season vegetables. But it’s also too early to plant summer vegetables out in the garden. You can buy starts of tomatoes, peppers and their ilk, but they need much warmer nights and warmer soil before they’ll be happy. So you’d need to transplant them into larger pots and keep them in a warm location for several weeks. Or just wait a while.
It’s not that we’re likely to have severe freezing weather at this point. Light frosts sometimes occur in March. On the other hand, we might have unseasonably warm days that make it seem like spring is fully under way. But nights are still cold, and the soil won’t warm up until April at the earliest. Roots in cold soil grow slowly. Plants have difficulty taking up nutrients. Leaves curl and turn yellow, and stems often turn purplish. Pests munch them faster than they put on new growth.
Continue planting young starts of leafy greens that you’ll use right away, such as spinach, kale, leaf lettuces, swiss chard and stir-fry greens. Try seeds of beets, carrots and radishes. Potatoes can be planted in fast-draining soil in raised beds and planter boxes.
You can get started preparing the soil for your summer garden. Mow off the winter weeds; it’s OK to turn most of them into the soil to provide organic matter. Spread an inch or two of compost. Buy bags of prepared compost, or have it delivered in bulk from the local rock yard. Make sure to include something that has some nitrogen: organic fertilizer, or chicken or steer manure, or both. It isn’t necessary to rototill, though you certainly may if you wish. Just water and let the worms and soil bacteria do their magic.
What about flowers?
Cool-season annuals you plant now will continue for another couple of months, giving lots of bloom very quickly. Then they will be replaced with summer flowers that you plant in April and May. Warm-season flowers aren’t any happier about early planting than warm-season vegetables. They sulk, discolor and barely grow until the soil warms up. So if you want some quick color right now, continue to focus on the winter annuals. Those include calendula, English daisies, Iceland poppies, pansies and violas, primroses and snapdragons.
Some flowers have a broad range of seasonal tolerance. Pinks and sweet alyssum can be planted year-around. Try some of the new Nemesia hybrids for a long season bloom. They’re likely to continue into summer, and can actually bloom again for a couple of years. Lobelia can go in now, and will bloom all summer. But I’d hold off a few weeks on fibrous begonias, coleus, marigolds and petunias.
Bad news about impatiens: This popular shade bedding plant is likely to be a thing of the past pretty soon. Downy mildew, a fungus that causes rapid defoliation and then death of the plant, is spreading across the country. The disease was first reported in the United States in 2004, and as of 2012 it had been found in 32 states. There is no remedy.
For your shade garden, we suggest fibrous begonias. Or choose from the many interesting perennials that are available for partial to full shade. Columbine, coral bells and other heucheras, and lamium are some of the easy perennials for shade.
Is it too late for fruit trees?
Bareroot fruit season is winding down, and most garden centers are potting up their trees now. You can still plant deciduous fruit trees in spring and summer. Expect to pay a bit more than you would have before they got containerized.
Citrus trees are on a different production and planting cycle. Orange and lemon trees and their cousins aren’t happy about being planted into cold soil. So the season for citrus is really just beginning. Young trees are available in garden shops now and all through the summer, and they transplant very well in warmer weather.
What’s that tree?
Our annual review of spring-flowering trees!
Flowers in February and early March? These early-blooming trees always prompt inquiries. First up are the almonds, plums and magnolias.
The white flowers of almonds are a hallmark of spring in the Sacramento Valley. Grown only in a narrow climate range around the world, California produces all of the U.S. crop and 80 percent of the world’s crop: from a billion pounds in 2003 up to 2 billion in 2012, grown on more than 750,000 acres. The almonds are in full bloom in late February and early March here.
You can grow almonds in your back yard in average soil, with a good soaking every week or so. Either plant two different commercial types for cross-pollination, or a self-fruitful variety such as Garden Prince or All-in-One.
Blooming right with them, even a little before in some cases, are the flowering plums. Two types are most common: Prunus blireiana (commonly called flowering plum) has soft pink blossoms on a tree that has green leaves; Prunus cerasifera Krauter Vesuvius (purple-leaf plum) has slightly darker blossoms on a tree with purple-red leaves. Both grow to 15 feet or more. A naturally dwarf red-leaf plum is also available. Purple Pony grows slowly to 10 to 12 feet tall, with a smaller, single pink blossom. There’s an even shorter, shrubby form of red-leaf plum called Prunus cistena.
The ornamental plums are easy to grow, tolerating moderately low water. Take care to get these fruitless types. Older varieties, formerly common in the nursery trade, produced prodigious quantities of messy fruit.
Magnolia soulangeana, the Saucer magnolia (sometimes called tulip tree), is in full bloom in the first week of March. It’s a short display, but well worth it. The most common variety is Alexandrina, which has a darker pink reverse on each petal. Some smaller varieties and species, including some with pure white flowers, are also in the nursery trade. Magnolias in general prefer plenty of water; they can tolerate lawn watering or be part of a flower border. Foliage will burn in hot weather if they aren’t watered sufficiently.
Along with the flowering pears (notable along Fifth and F streets), these above are the first to bloom. Redbuds also have started to bloom this week. Some later-flowering trees in March and April include crabapples and flowering cherries.
* Technical stuff: I don’t understand “chilling hours.” Trees need them? What are they, how many do trees need, how many do we get here?
Last question first: In the period from November 2012 to February 2013, the Davis weather station recorded 1,048 chilling hours. That is the number of hours between 32 and 45 degrees (F).
Many deciduous trees require a certain number of those hours of chilling (not freezing) in order to come through dormancy and open their flower buds properly. The amount they need differs by variety, usually from 400 to 800 hours. This year’s total is above our average of the last 15 years or so, but very close to what we’ve had for the past five or years. Chilling hours in this area have been above 800 hours consistently for the last decade (above 1,000 hours, mostly). So we get plenty.
If you live in the Bay Area or Southern California, you need to be attentive to chilling hour requirements as you purchase fruit trees. My mother, in coastal San Diego, gets less than 100 chilling hours. Most deciduous fruit varieties won’t bloom properly there. Trees that don’t bloom properly don’t fruit! So we don’t need to worry about this, but gardeners in mild-winter regions do.
Anybody in California can check the chilling hours at a nearby weather station, thanks to this site maintained by UC Davis: http://fruitsandnuts.ucdavis.edu. Look for the “Weather Related Models.”
Spring is just around the corner!
* Note: On Wednesday, March 13, from noon to 1 p.m., you can walk through the Warren G. Roberts Redbud Collection at the Arboretum with Roberts himself. The Western redbuds should be in full bloom. Meet at the Arboretum headquarters. For more information, visit arboretum.ucdavis.edu.
— Don Shor and his family have owned the Redwood Barn Nursery since 1981. He can be reached at email@example.com. Archived articles are available on The Enterprise website, and they are always available (all the way back to 1999) on his business website, www.redwoodbarn.com