Timing Fertilizer Applications in Orchards for Bloom. And Why it Matters.

Citrus bloom is in full swing here in the Central Valley. It comes not too far behind the vernal blooms of other popular orchard trees, such as apples, peaches, apricots and more. Like most growers, you want to ensure the success of your crop— and for fruit growers, a lot can be on the line just as soon as the buds begin to break. It’s enough to make some growers wonder: can you time fertilizer applications in orchards during blooming season? Will applications during citrus bloom even help?

Again, it’s natural for any grower to want to help their crop along in any way possible— and using fertilizer can bring a lot under your control. But when it comes to fertilizing for the best fruit blooms – and the best fruits later on – there are a few things growers should know about timing, amounts, frequency and more.

The best time for fertilizing for fruits is now (springtime)

If you’re concerned about the welfare of orchard blooms specifically  – and the buds are already up –  the bad news is the time may have already passed to help these flowers out. But don’t despair. The good news is there are some fertilizer applications for your flowers you can still get in for the benefit of the next stage to come: fruit set. Come flowering season, the nutrients your trees would need for the event have been long taken up ahead of bud break. In fact, in Mediterranean climates (as in the Central Valley) the perfect window for feeding orchards in preparation for the strongest, healthiest blooms is in winter according to Robert Crassweller, Ph.D. That said, very early spring applications may help but only if timed well before bud development.

Practically all plants that go dormant in winter – including fruit trees – focus on building energy and nutrient reserves at the roots which they then tap into come spring. Any root-based fertilizers (compost, chemical NPK, etc.) applied after the fact won’t reach the blooms where or when they need to. What growers can do once buds are up— or flowers are well-developed— is a apply some foliar fertilizers. Calcium always helps, but the key micronutrient for big, healthy, appetizing fruits is boron, which can still be applied when trees are either budding or blooming. Be sure to follow recommended amounts and directions, as excessive boron can bring diminishing returns. Avoid adding boron if you have fertilized trees with this micronutrient sometime within the past 3 years, according to the University of Maine Extension.

Keep track of your yearly fertilizer applications

Don’t rule out the possibility that your trees are already plenty well-fed in advance of the blooming season. As the saying goes: “don’t fix what ain’t broken.” Orchards that are adequately fertilized through the previous year (receiving at least one-tenth of a pound of nitrogen-forward fertilizer per year of tree age, once per year) will be plenty equipped for next spring. Most fruit trees draw from the nutrient and energy reserves from the previous year during summertime before heading towards dormancy, then tap into that energy first thing come blooming season. 

The trick is: knowing if you need to fertilize or not. In fact according to Iowa State University Extension, fertilizing orchards and fruit trees may not even be necessary  — unless there are some real deficiencies — growth problems, or diseases taking place.This is why keeping track of annual fertilizer applications at the root is highly recommended from year to year, especially with nitrogen amounts: how much did you use? Are your trees growing enough? ISU Extension says fruit-producing trees should be on track to grow around 12 inches of new growth on average per year (between 8 and 15 inches).

Growers should also consider that too much fertilizer isn’t always a good thing. If excessively applied or wrongly timed (such as amending in late spring or summer) a few things can happen. First, the excess nitrogen can favor stimulation of foliar growth over floral/fruit growth. Further, if too much growth takes place from fertilizing, the new growth can be more vulnerable to cold damage the following winter. It is ultimately a waste of fertilizer, and a net gain for growers.

Over-applying or amending your fruit trees can have diminishing results for both flowers and fruit— and for yields and profits down the line. Don’t change what’s perfect already; keep detailed logs or records of nitrogen fertilizer applications through the year, and don’t go over your trees’ yearly nitrogen needs. Similarly, keep records and logs of other fertilizing nutrient applications, such as boron or calcium, to make sure you aren’t applying more than needed at the detriment of your yields.

Plan ahead for the coming year

Missed the boat on key fertility applications this year? Too late to nourish fruit blossoms? The next best thing: establish a plan for the coming season, or even for the whole year ahead, to best time fertilizer applications for your orchard bloom. In some areas outside of the Central Valley, it still isn’t too late to add nitrogen fertilizer to your trees. It may not benefit this year’s blooms, but it could certainly benefit next year’s.

If you’ve followed most fertilizer guides and are still concerned about blossom health or appearance— or you have continued issues with growth— it may be a good idea to implement a soil test of your orchard as the next best practice, especially if you’ve never tested before or for a long time. A nutrient deficiency could be at work here: most likely calcium, boron or phosphorus, though in some cases other micronutrients could play a role as well. Fruit trees, like all plants, need a wide spectrum of nutrients in order to enhance the uptake of all nutrients together.

If you’re looking at your orchard bloom right now and wondering what you can do to feed those beautiful blossoms, don’t fret — you’ve got options for both right now and the future.

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