Can someone explain ultra-dwarf and genetic dwarf fruit trees?

ashleysf(9 San Jose,CA)February 24, 2010

I have seen most of the popular local nurseries carry both the "ultra-dwarf" and the "genetic dwarf" type of fruit trees this year (similar terminology to Condo mangoes!). Since I am not familiar with what they are, I have mostly walked past these trees. I have purchased all my trees as either "standard" or "semi-dwarf" trees.

Now about this miniature trees, do they produce enough fruit?

What makes them so small?

Do they require pruning?

What is the life expectancy of such trees?

And anything else interesting that you may want to add?

Thanks in advance for sharing your knowledge.

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fruitnut Z7 4500ft SW TX

Ultra dwarf and semi dwarf refer to effects on tree vigor brought about by choice of rootstock. Genetic dwarf is bred for low vigor of the scion independent of any rootstock effect. Some of the genetic dwarfs, esp peach and nectarine, have very compressed internodes. So the leaves and fruit buds are very close together on each limb. I'd hate to have to thin all that fruit out of all that dense foliage. Also the dense canopy could lower fruit quality and aggravate pest issues. But the reason I've never planted a full out genetic dwarf is because of perceived lack of fruit quality.

There are large differences in cultivar vigor independent of rootstock effects. Some cultivars just grow a lot less than others but don't have the compressed internodes. I've seen this in apple and plum/pluot. Dave Wilson just released a dwarf apricot, Pixie-Cot.

I do a little pruning even on the most dwarf combinations I've got. Too little vigor can be worse than too much. Just depends on the situation. With some of the less vigorous pluot there may not be enough foliage after a few years esp in the bottom of the tree.

    Bookmark   February 24, 2010 at 9:46PM
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Ashley (just sent you an email),

We only live a couple hours apart and we see the same trees at big box and nurseries. You're probably seeing "ultra" on the Pacific Groves trees, right? Some are in bags (bareroot) at various places and some in the fiberpot containers (Lowes). If so, you can drop the term "ultra" and just consider it dwarf. Dwarf and semi-dwarf are what you're aware of: "regular trees on lower vigor rootstocks". These are prolific at nurseries and big box stores alike. Genetic dwarf, aka Miniatures or "true dwarf" are more rare, they are "dwarf trees on whatever (typically regular sized) rootstock".

I think you already understand stocks especially how dwarf stocks ideally encourage fruit at younger age (early bearing) and retain a heavier fruit set (precocious). Each stock is different in various properties like size reduction, early bearing, preciousness, disease resistance, soil tolerance, and so forth. The rootstock is *mostly* what makes dwarf and semi-dwarf so small -- the lower vigor. The scion of certain varieties can be somewhat dwarfing and so can their tolerance of summer pruning. It ALL depends on variety, rootstock, and growing conditions. Thus why I've spent countless hours researching the various stocks and varieties before I go buying and planting gobs of them in my yard.

Take the Babcock peach, very common. It can be grafted onto Lovell as full sized, on Citation is considered semi-dwarf, on Pumiselect called dwarf (PG calls it Ultra) but Babcock will never be a miniature (genetic dwarf). Just as Necta-Zee (another newer genetic dwarf) will never be a semi-dwarf or full sized tree.

The mini's are very small, though their size differs based on variety, but many are 3 feet tall (unpruned) after 2 years old in the ground, whereas the PG ultra-dwarf could be like 6 feet by then.

LE Cooke (near Visalia) also produces miniature trees, but I'm not sure the volume since I've only found a couple local nurseries that have ever had any -- and those nurseries don't plan to stock them anymore. The folks at LE Cooke have not responded to my inquiries.

Nevertheless, they have an awesome website with cool photos of their genetic dwarfs.

Here is a link that might be useful: Take a look at LE Cooke's Site

    Bookmark   February 25, 2010 at 3:40PM
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I've asked all these same questions here.

No they don't require pruning but a big YES they require root pruning if you're keeping them in containers. From a root prospective only, it's like growing a full-sized tree in a small container. You'll probably be *required* to root prune every two years.

Search for "genetic dwarf" in this forum and you'll see the LifeSpan question was posted just a couple weeks ago. You'll find many other posts about genetic dwarfs also.

Yes it does produce fruit. It is supposed to produce "more per square footage" than a typical tree. I think they mean "more per cubic footage" since they are so short. This is because of internodal spacing fruitnut mentioned. The leaves and fruit are spaced much closer together.

About Flavor -- I don't know myself (yet). I should know something with this crop, but only from two of my trees. Supposedly the fruit is inferior -- but I won't believe it until I try it. I know they have unfairly received a bad name from one mini in particular -- the BONFIRE. It was sold by Lowes and LE Cooke as "ultra dwarf patio trees" with "tasty fruit". It is now known to produce very poor fruit, nearly inedible (not poisonous) crunchy and tasteless. There are also new varieties that are supposedly great tasting -- but I'm pretty sure no mini tree's fruit taste great unless thinned properly.

    Bookmark   February 25, 2010 at 3:59PM
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BTW I believe Fruitnut is speaking mostly from the mini apple prespective, if I recall correctly. All my comments above are regarding peach/nectarine miniatures only. DWN does sell the Pixie-Cot and a Garden Delight mini apple -- I don't either yet.

    Bookmark   February 25, 2010 at 4:03PM
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ashleysf(9 San Jose,CA)

Thanks a lot cebury and fruitnut. I am always learning on these forums.

In case you are still looking for more genetic dwarf trees (and traveling to Norcal), Probuild garden center in Santa Cruz had almost all the DWN genetic dwarf trees (bare root) and at reasonable prices too when I was there 3 weeks ago. You can give them a call to check availability.

    Bookmark   February 25, 2010 at 4:30PM
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