Sunny Slope Orchard

Sunny Slope Orchard
In the coast range foothills overlooking the Sacramento Valley

Monday, January 27, 2014

Pruning citrus trees

A well pruned citrus tree has open space inside
As with all fruit trees, citrus benefit from regular pruning. Though they require less radical work than many fruits, regular pruning provides several benefits:

  • It maintains the tree at a manageable size. Left unpruned a citrus tree will continue growing higher and wider each year until eventually reaching 20' or more. It is common to see unpruned citrus trees hanging over neighbors' fences and rubbing on roofs. Even dwarf citrus will easily grow too tall, they just take a bit longer.
  • Pruning allows light and air inside the canopy, improving fruit quality and quantity and reducing pest infestations. Left unpruned the foliage becomes so dense that deeply shaded areas stop bearing and small branches die back. Mites and scale insects thrive in the dark crowded spots that tend to stay damp. A well pruned tree is a healthy tree.
  • Pruning makes harvest much easier. Over time small dead twiggy branches accumulate, making picking difficult and painful. Cutting out the dead and thinning the crowded shoots really improves access and visibility. I like to maintain big enough openings around the canopy that I can step inside.
  • Keeping branches up off the soil prevents fruit mold and limits access for ants and other pests.
Dead shoots clutter up a grapefruit tree

The same view after pruning out dead wood and crowded

Before pruning . . .

 . . . and after

Vigorous upright shoots called "water sprouts"
should always be removed. Left alone they quickly
grow right through the top of the tree and they
seldom produce decent fruit if any.

Water sprouts can be recognized by their
flattish shape and are often thorny

These naval orange trees maintained at no more than 7' high
can be picked without a ladder. Lower branches are pruned up
off the ground so the lowest fruit will not touch moist soil
and get moldy.

The view from inside shows the open spaces created by pruning.
These oranges can be picked without getting scratched hands.
When to prune
Heavy pruning on a neglected citrus tree is best done in the late winter/early spring before the spring growth spurt. Then strong spring growth will nurture the tree to recovery. If topping the tree to reduce its height exposes bare bark to the sun, be sure to paint those areas with 50/50 white interior latex paint and water to prevent sunburn.

But for trees that are regularly maintained, pruning time is not so important since little growth is removed each time. I normally do touch-up prunings twice a year, in late winter and again in mid summer as needed to control height. Since pruning promotes new growth, late summer pruning should be avoided since the new growth could still be tender in early winter and easily freeze damaged.

Monday, January 20, 2014

Drought times four

A bone dry pond and parched hills on a nearby property. The
pond normally fills by December, providing water for grazing cattle.
Well, these past few days the media has suddenly awakened to the fact that California is in the midst of a drought. Stories of low reservoirs and dry river beds abound. But to those of us who depend directly upon the annual rainy season to fill our wells and irrigate our crops, this is old news. For us every fall begins an anxious time of hoping for rains, preferably in the form of generous storms at regular intervals. But this season's weather has dashed our hopes early, often and cruelly, not just from lack of winter rains alone but by four compounding factors.

First, so far this year we have had barely 2" of rainfall, and have had none at all since December 6. That is the longest mid-winter dry stretch in the 150 years that records have been kept. At our 800 ft. elevation we normally average 35 inches of rain per season, most falling between October and April. So what should be emerald green hills saturated with water are instead still golden and parched. Our ground is bone dry except where we can manage some minimal drip irrigation from our low-producing wells. And those wells, which would normally be recharging this time of year, are continuing the drop that started at the end of last year's rains. Long range weather models predict little chance of significant rain this spring.

Second, the previous two seasons have been quite dry so we started out this season in the hole. The 2011-12 and 2012-13 seasons gave us only about 60% of average, so we entered last fall with a two year deficit. We have been through droughts before, notably three years in the mid-70's. But then we got at least 10"-13" of rain each year. Right now 10" would seem like a bonanza.

Third, except for one very cold week most of our fall and winter days have been unseasonably warm and sunny. Temperatures have regularly reached into the 70s. While the tropical temps are pleasant for working outside they quickly dry out plants and soil, requiring us to winter irrigate, something the rains normally do for us. And even that freezing cold week hurt, since cold air is very dry and pulls moisture out of everything.

And fourth, we have had an unusually high number of days of north wind, including several multi-day episodes of horrendously strong blasts. As anyone who lives in northern California knows, north wind is a fiendishly dry, irritating weather occurrence that desiccates plants and people, often blows with destructive force, and makes us all grumpy. In addition to sucking away any moisture we received from our measly rains, the strongest windy spells scoured the floor of our orchard, clearing off most of the fallen leaves and other mulch that normally provide protection for the soil surface.

So we are hoping for the best but preparing as well as we can for the worst. I spread compost and planted a legume cover crop as usual last fall. A couple of light rains were enough to germinate the seed, but since then it has been barely clinging to life.

This legume cover crop would normally be waist-high
and lush by now
It is important to keep the orchard trees' roots hydrated even during the dormant season, so since early December I have been moving circles of drip tubing from tree to tree. This boosts the cover crop directly under the trees, but more importantly helps to store some water in the soil for even drier months ahead. With our limited water supply I can only afford about four hours of soaking per tree, three trees at a time. This means each tree gets this tiny ration only once every 20 days or so.

Drip irrigation tubing circling a tree
Ground water is notoriously short in our area, and the aquifers that do exist mostly flow through small cracks in sandstone or shale. So although there is some water underground, it cannot flow quickly into a well. This means that water has to be pumped slowly from the wells into large storage tanks above ground. That way we can accumulate it while we are not watering and have a temporary supply for fast use when we need it.

One of our four water storage tanks sits on the highest spot
on our property, providing gravity pressure for drip irrigation.
A rope and float system indicates water level in the tank.
We have four wells, all low producing. Together they produce around 1000 gallons per day. While that might sound like a lot, a single inch of rain falling on our 4 acres would deliver 110,000 gallons!

Our original well is pictured below, an old hand dug hole in the ground that is only 36 feet deep, 4 feet in diameter at the bottom and lined with random sandstone rocks placed without mortar. It is likely over 100 years old, and one has to marvel at the immense and dangerous labor required to construct a well like this.

The beauty of a dug well is it's volume - it acts as a storage tank in the ground, accumulating water whenever we're not pumping. We have a solar powered pump in this well, and since it only pumps during daylight the water level recovers overnight. Surprisingly after an average rainfall season this is our best well, holding a steady 12 to 15 feet of water inside. Sadly, during dry years the water level falls sharply and is now only about 2 feet deep in the mornings before pumping.

Our old hand dug well
So for now we search the long range forecasts daily for signs of hope, trying to stay optimistic but knowing we are experiencing a drought unprecedented in California recorded history.