Avocado Seedlings

Avocado seedlings can pop up almost anywhere in the garden.

We had one grow near our incinerator, another came up in the compost heap, then there was the one by the deck, the seedling tree right outside the kitchen window. All these trees fruited (eventually). We named the fruiting seedlings ‘incinerator’, ‘compost’, ‘deck’ and ‘kitchen’ – thereby displaying a keen sense of geo-location, rather than a lack of imagination.

As we have a small rural ‘lifestyle block’ with some patches of soil suitable for avocado, we were able to plant 10 or so cultivars, as well as planting a few seedlings for later grafting (mostly from commercial fruit, mostly Reed, some Hashimoto, a few probably Fuerte).

My grafting skills are rather poor, and some of these few ‘rootstock seedlings’ grew on to produce fruit. I left a rootstock stem ungrafted on five of the rootstocks I did successfully graft. Although these trees are currently very badly affected by Phytopthora, several have had some flowers and even produced a pathetic sized fruit.

As anyone with a group of larger avocado trees will confirm, seedlings germinate endlessly from fruit fallen under the canopy. Like most people, I spray them out. But the odd one escapes attention.

Almost all self-sown seedlings are commercially useless – as are deliberately sown seedlings (whether sown by plant breeders or a home gardener.) Almost all, but not all seedling are useless. Self sown escapee seedlings in commercial avocado orchards have given us the commercial varieties Pinkerton, Maluma, and Reed.

A few avocado cultivars are more likely to give worthwhile seedlings – even if there is a fault (such as thin skin) which prevents them from being commercially acceptable. The best seed parent is Hass, and as it is almost the only cultivar grown (in Mediterranean and warm-temperate climates), most seedlings will have Hass as the female parent. Hass is self fertile – a big part of its commercial success – and so many chance Hass seedlings will be selfed.

Dr. Bob Bergh’s experience (Bergh 1976b) is that Hass is “probably the best of all progeny-tested parents”. Of 400 selfed seedlings, 18 were found worthy of selection for further study (1 in 22).

Since Bergh’s time at the University of California, the emphasis has shifted. Gwen, a seedling of Thille, has been found to be an outstanding maternal parent. Gwen and Gwen progeny (Harvest, Nobel, Marvel, Gem, 5 -552, Lamb Hass) have been used very extensively in the Californian breeding program.

But Gwen has never really gained much traction against Hass, the fruit are simply not available in New Zealand shops (and barely available in the USA) so the average random seedling is still likely to be a Hass seedling. And if it fruits it is likely to fruit at around the same time as Hass – and is highly likely to be inferior to Hass.

From a home garden perspective, the best seedling would be one that fruited in winter, and is good quality. Fuerte should be the number one choice for winter, but it is a large spreading tree, and is a very erratic bearer.

Fuerte seedlings, whether deliberate or accidental, are a waste of time and space. Selfed Fuerte seedlings were “markedly inferior” according to Bergh (1976b). He went on to comment that most [selfed] Fuerte seedlings “never set fruit, and most setters have fruits of deplorable size, shape and seed ratio”.

Mexican avocado cultivars have a much shorter time to maturity, are oily, and seedlings of Mexicola, in particular are quite precocious. Pity the tree is huge, and the cultivar no longer available (in New Zealand, at least).

In the long run, molecular techniques enabling selection for specific desirable characters will result in more and better commercial cultivars (hopefully, including season extension into winter).

As a result, in the distant future, home garden seedlings, whether chance or planted, will be much more likely to be desirable. But it’s a slow process, and it’s probably many decades away.

In the meantime, in the spirit of Dr. Berghs short reports on seedlings that ‘didn’t make it’, I will post photos and comments on random home garden seedling found here, both past and present.

Check the index under ‘seedlings’.

Bergh, B. O. 1976(b). Factors Affecting Avocado Fruitfulness. In: J.W. Sauls, R.L. Phillips and L.K. Jackson (eds.) Proceedings of the First International Tropical Fruit Short Course: The Avocado. Pages 83-88.
Gainesville: Fruit Crops Dept., Florida Cooperative Extension Service. Institute of Food and Agricultural Sciences, University of Florida

Bergh, B. O. 1967. Some late-maturing avocado seedlings of various parentage.
California Avocado Society 1967 Yearbook 51: 131-158

Bergh B.O., and Whitsell R. H. 1973. Self -Pollinated Hass Seedlings.
California Avocado Society 1973 Yearbook, 57: 118 -156

Bergh B. O., and Whitsell R. H. 1975. Self -Pollinated Fuerte Seedlings.
California Avocado Society 1974 Yearbook, 58: 128-134