Year 2

OK, went a while without updating this blog. The remaining avocados dropped off the tree last summer, so there wasn't much to post about.

Tree has just finished blooming, starting around the same time as last year. Until ~2 weeks ago there didn't seem to be any fruit set, but all of a sudden little fertilized avocados started popping up. Whereas last year I counted at most 4-5 blooms that set by the time the flowers dropped, this year I've counted up to 3 dozen at any one time. Exciting!

At the end of February I grafted three scion branches of other avocado varieties onto my tree, being awed by the "4 in 1" trees you sometimes see in nurseries and being eager to learn about how asexual reproduction is performed on fruit trees. I grafted a scion of "Hellen", "Sharwil", and "MaGoon" onto various branches on the tree, scions that I got from Julie Frink at the California Rare Fruit Growers scion exchange in Orange County. As she warned me, none of the grafts actually survived, but it was a learning experience, and next year I think I will try grafting onto a seedling.

That's all. Hopefully a small handful of fruit will stick this summer, though I am expecting most to drop when it starts to get hot.

Summer heat

8/12/2012

 It's been really really hot lately, but the tree is doing fine -- great, really. Another flush of new growth started about a month ago and the tree looks really nice overall. One fruit fell only a week after my last post, leaving one avocado left. The remaining fruit is about as large as a yo-yo and growing nicely.

If you forced me to guess, I would say that the switch from thrice-weekly deep hose waterings to the daily drip waterings was a minor shock to the tree and convinced it to drop some fruit. But I'm not an expert. So as of mid-June, our Holiday avocado tree has a single fruit on it, and with luck it will stay there until maturity.

There are no signs of sunburn on the tree, which is great given how much heat we've had recently. Our yard gets quite a bit of shade in the winter from a large tree in the neighbor's yard. We knew this when we planted

Another flush of growth
started late July.

our Holiday, but decided that its current spot was the best/only spot in the yard that would work well despite the winter shade. The tree gets full sun in summer and seems to be enjoying it. Since planting day, it has grown about a foot and is creeping above its support stake. The nursery had pruned the main trunk at
about 5 feet, but several branches went outward from there and have risen almost a foot higher.

Drip irrigation system. Half of the arcs of the
"circle" around the base are "soaker"
lines, the other half are standard
1/4" feeder lines.

Drip irrigation

~45 days, size of a thumb.

Our two fruit are growing nicely, and the tree looks quite happy overall. I added some more white-wash (half interior latex paint, half water) to some of the branches that were looking a little sun burned. 

Our drip irrigation system has been running for about 2 weeks. I run it manually every other day for 30-40 minutes, on the same schedule as our raised garden bed because the drip lines are connected. Today, however, I installed 3-outlet hose timer from Orbit and ran a second 1/2" supply line to the avocado tree so that it can be on a schedule separate from the garden. During summer months, we will water the tree every day for 60 minutes, and every other day 25 minutes for the garden. That schedule will be cut back in the fall and winter to give the tree less water in the cooler months without affecting the water needs of the garden.

The system has three 1 GPH drip emitters arrayed in a circle around the tree, with two more spurring out from that circle. Of the lines that connect each emitter in the circle, half are 1/4" "soaker hose" lines that drip water along their entire length. The others are regular 1/4" irrigation lines. I added the soaker lines today because I was concerned that the tree wasn't getting quite enough water. 

Fruit set

Fruit set, aged ~12 days?

About 10 days ago I noticed a few fruit had set on the tree. Exciting! But it's best to stay cautiously optimistic: avocado trees are known to set many, many fruit, and drop a good deal of them over the next few months, particularly as the weather warms up. I had counted as many as 8 fruit set at one point, but only a week later we are down to just 3 left.

If this tree were younger we would probably remove all the fruit. Since it's probably a year older than most nursery plants, we're going to leave these fruit on and see how they do. In all likelihood they will probably drop over summer; I don't know of any real scientific testing about the subject, but Internet wisdom says that an avocado tree won't keep a fruit until its base is 3-4 inches in diameter (ours is at most 2 inches). We'll just cross our fingers.

I will be installing a drip irrigation system soon, having thoroughly researched the subject. We have a small raised vegetable garden that is serviced by drip irrigation already. I will need to dig a trench to run the water supply line and digital control wires under the lawn, but once that is set the system will be completely automated. Currently I plan to put a single 2 GPH drip emitter on either side of the tree, and run the system every other day for 45-60 minutes. That will save J a lot of time and stress while I'm away for the summer.

New leaves

A full branch of new leaves.

Along with flower buds, the tree has been growing new leaves from all its branches. The leaves are a nice reddish color indicating strong growth. Leaves grow out of the ends of each stem and slowly "fold" out as the stem elongates. Lower branches are have produced more new leaves than upper branches, but all branches are pushing. The tree looks much happier with the vibrant new growth than it did after the initial burning of the leaves from lack of water.

Old leaves being sucked of strength.

As the new leaves are pushed out, last year's crop of leaves are dropped by the tree. Old leaves are "sucked" of nutrients to help support the new leaves; the old leaves turn brown in the middle along vein lines, contrasting with the brown tips from water stress.

First bloom

First flowers are blooming.

A male flower. When female, only a
single "stem" will stick up in the
center of the flower.

Holiday is an "A" type avocado tree, which means its flowers follow a certain pattern of opening and closing that differs from "B" types. Common "A" types include Hass, Holiday, Reed, Mexicola, Pinkerton, and Gwen; common "B" types are Bacon, Fuerte, Kona Sharwil, and Zutano. All avocado flowers have both male and female organs, and shed and receive pollen at different times. An "A" type flower opens in the morning as a female flower, closes after a few hours, and then opens the next day in the afternoon as a male flower. A "B" type flower opens in the afternoon of its first day as a female flower, closes, and then opens the next morning as a male flower. Notice that when an "A" type is open as a female, a "B" type is also open as a male, which makes pollination much easier, and in fact commercial groves plant a few "B" types among their "A" types (Hass being the only avocado grown in large quantities in California). All avocado flowers close permanently after their second day, and either fall off or start the process of growing into a fruit.

 This all apparently goes out the window in California. Avocados come from tropical regions in Latin America and the West Indies where things are much warmer; in the slightly cooler California climate, the flowers' internal clocks get thrown off a little and you will often find both male and female flowers open at the same time. For this reason avocado trees are considered semi self-fertile. I have seen male flowers open until midnight, and regularly find flowers of both sex open at the same time.

Fertilizer

Flower buds forming in late February/
early March.

Most experts recommend at most a very light fertilization for young trees. I went with half the recommended amount of organic citrus & avocado fertilizer from E.B. Stone. Too much fertilizer can burn the roots, and  fertilizer heavy in nitrogen can apparently push too much foliage growth over fruit development. Animal manures are too heavy in salts and will hurt the tree, so stick to something designed for citrus and avocado.

The tree has stabilized after its planting. The brown tips have progressed a little further up most leaves, but flower buds seem to be forming, and there are a lot of branches that seem to be preparing for a growth spurt. (Ends are opening up, small new leaves are forming, and it just looks "ready to go.")

Planting day

We planted our Holiday today!

The tree is a 15 gallon* Holiday (XX3) avocado tree that J gifted me for Christmas. It has been in its nursery container for the last month while we prepared the planting site. It is currently about 5 feet tall, its main trunk having been pruned by the nursery some time ago.

We planted the tree on a mound that comes about 1.5 feet above ground level. The soil in this part of our yard was very very sandy -- good because it should drain well. We mixed in "Bumper Crop" planting soil to raise the mound and give some nutrients. The tree is planted at the apex of the mound, and the whole mound covered in ~3 inches of medium bark and cedar shaving mulch.

After reading about problems with salty tap water in southern California, we applied 10-20 pounds of powdered gypsum all over the mound. Sources say that gypsum will help keep salts from moving into the roots and leaves of the tree. It also is one of the rare ways to get calcium into the soil without raising pH levels.

The tips of most leaves are browned, likely from under-watering the tree while it was in its nursery pot. Some branches are also a little brown and damaged. I first thought this was due to sun damage, but with the benefit of hindsight (writing this in April) I am certain it was too little water.



* Many people recommend against buying a 15gal tree, saying that they are often root-bound and do not grow as vigorously when finally planted. We bought the 15gal hoping it would produce fruit sooner than the smaller trees; also, since we have little experience in growing things, we wanted a tree that was already a strong grower.

Things I've learned about avocados

So, some important things I've learned about planting and caring for an avocado tree.

• They NEED fast-draining soil. Avocado trees really suffer in heavy soils and are more susceptible to root rot in wet conditions.
• They are sensitive to salts in their water supply. In SoCal we have alkaline and salty tap water, which burns the tips of leaves as the salts build up. (It also raises the pH, when the tree prefers slightly acidic soil.) Deep waterings can help flush salts from the soil. Using gypsum powder helps bind the salts so they stay out of the tree.
• In the wild, baby avocado plants grow up under the shade of larger trees, and because of this get sunburned easily when left in the sun at a young age. They can be painted with white interior latex paint diluted 50% with water to protect against sun damage.
• To help keep the soil from getting water logged, it is recommended to plant avocados on mounds. 
• Trees appreciate heavy mulching, 3-6inches recommended to provide nutrients to the shallow feeder roots and protect them from sun damage.

Why a Holiday?

So, why did we choose a Holiday avocado?

1. It is a natural dwarf/semi-dwarf tree. Various sources list it at 10-15ft tall full grown, and about as wide. We have a smallish back yard in Southern California and did not want to dominate it with a 30-ft Hass tree.
2. It's different. We can buy Hass at the supermarket, and most farmers' markets also sell Fuerte and Bacon. Holiday is different and interesting.
   
3. The fruits get very large (15-18oz; as a reference, Hass is usually 8-10oz).
4. Julie Frink lists the flavor as XLNT.