Apple Rootstock

Standard and semi-vigorous rootstock usually cause their trees to take awhile to produce since they do not induce precocity like the others, but high vigor is often desired for relatively dry climates, since they are more drought tolerant, or if deer frequent your area. Their large size will, unfortunately, make them difficult to spray and harvest, if the former is required. Apple rootstocks with less vigor often require permanent staking. Some of them, however, may only need to be staked for a few years (if at all) when they are planted in deep, well-drained soils that aren't too light, but in less than ideal soil types, it may have to be permanent.

For rootstocks that aren't entirely reliant on staking, planting deep can help stabilize the tree, but the graft union should be at least 2 to 4 inches above the soil to ensure that the scionwood does not root. This can also be done to rootstocks that are prone to burr knots, since they do not form underground. Overall, planting deep is a practice that seems to work fairly well with apples, provided the soil isn't too heavy or wet, but it should not be done to species that are more sensitive or difficult to root, since roots need oxygen and excess moisture can deteriorate the wood.

Many of these low vigor rootstocks come from the relatively new Geneva series, and they often share a number of positive traits, such as resistance to fireblight, crown rot, woolly aphid, and latent viruses. They also have the fairly unique attribute of resisting the negative effects of replant disease, but this is only needed if you plan on planting an apple tree in a location that recently had one. Furthermore, Geneva rootstocks are quite precocious, resist burr knot formation, and are less likely to sucker than some of the older selections, but a number of them may form weak unions when bark grafting is used. In fact, they are occasionally mentioned for creating trees that are less likely to survive, as if they were more fragile in some other way, than those grafted to selections that have been around for a longer duration, so if you don't require additional pest and disease resistance, and if none of their other advantages catch your eye, then you might be better off with something else.

Standard: Antonovka, Dolgo, and Ranekta

Seedlings are generally used for standard rootstock, such as those from the Antonovka strain. There isn't very much information about Antonovka, and some of it is contradicting. For example, they are occasionally mentioned for being hardy down to zone 2, but zone 3 or 4 is likely more accurate. Additionally, some sites claim they do not sucker, but I have seen enough to doubt the legitimacy of this. As I have implied, it is hard to be certain and there may be some variation between them, even if they are relatively true to seed, but I believe that Antonovka often demonstrates some resistance to collar rot as well as some susceptibility to fireblight.

Dolgo crabapple seedlings are also somewhat common, and it sounds like they, too, have some resistance to collar rot. Information about fireblight, while easier to come by, has also been quite contradicting, but it leans towards the implication that they are at least somewhat resistant to this disease as well. Dolgo should be hardy down to zone 3, making them relatively tolerant of the cold, but seedlings from the cross referred to as Ranekta (Malus baccata x Dolgo (Malus x robusta)) are the most cold hardy standard rootstocks that I am aware of (zone 2). However, Malus baccata seedlings are hardy down to zone 1, but they may not produce standard-sized trees. They are less vigorous, but this helps them bear at a younger age. Baccata is also more prone to suckering, and they supposedly have compatibility issues with some of the more "developed" varieties.

Semi-Vigorous: Bud 118 and MM111

Budagovsky 118 (Bud 118) is similar to MM111 in that it is somewhat resistant to fireblight and crown rot, but it bears earlier, it does not sucker as much, and burr knot formation is not as frequent. However, the primary advantage of this rootstock is that it is one of the more cold hardy selections (zone 3 or 4). Some of the disadvantages of Bud 118, when compared to MM111, is that it is not as tolerant of heavy soils, as well as those that are relatively wet or dry, and it is likely susceptible to woolly aphid.

EMLA 111 (MM111) is, perhaps, the most resilient rootstock available in North America. It is suitable for a wide range of soils, provided they aren't too wet (since it is only somewhat resistant to collar rot), and it is implied to be the most drought tolerant. It has some resistance to fireblight as well, and it has good resistance against the woolly aphid. Unfortunately, it has a reputation for being slow to bear, and it is fairly prone to suckering and burr knot formation. Lastly, MM111 is not as cold hardy as some of the other rootstocks. I haven't seen any numbers, but it seems to handle zone 5a temperatures just fine.

Semi-Dwarfing: M7, G890, G969, and M26

Geneva 890 (G890), EMLA 7 (M7), and Geneva 969 (G969) may benefit from staking for a few years, especially if you let them crop heavily at a young age, but they are frequently grown as freestanding trees from the start, particularly when they are planted in deep, well-drained, fertile soils that aren't too light. High budding and deep planting can also help keep the tree stable, as I have mentioned. G890 and M7 are similar in size, and the climate will likely determine which will end up being more vigorous. Geneva 969, on the other hand, was originally thought to be slightly smaller, but additional trials indicated that it may be closer to that of EMLA 26, meaning that it could be much smaller in comparison.

EMLA 7 demonstrates precocious behavior, but to a lesser extent than G890 and G969. It does not share the same level of resistance to fireblight and crown rot as them either, and while information about it is somewhat contradicting, it doesn't seem to be especially weak or strong to either disease and it generally leans more on the positive side.

A few other disadvantages of M7 is that it can sucker quite profusely, and it is more likely to produce burr knots. However, it is much easier to graft, and they will likely form stronger unions. EMLA 7, as well as most other EMLA rootstocks, may be more resilient in general when disease is not an issue, considering that results from home-growers concerning the performance of trees that were grafted to Geneva rootstocks have been a bit too variable to ignore. This may not give EMLA 26 a significant advantage over G969 though, since M26 is susceptible to fireblight, crown rot, and burr knot formation, and in climates where they are suitable for use, such as those that experience a low to moderate amount of rain, additional attention to irrigation may be required, since it develops a weaker root system.

Dwarfing: G214, Bud 10, G11, Bud 9, and M27

Geneva 214 (G214) resides somewhere between a dwarfing and a semi-dwarfing rootstock when grown in a fairly wet climate, but in a dry climate, it grows much smaller, much like the others within this series. This is where the additional vigor from G214 may end up being quite beneficial when it is compared to G11 (another one of Geneva's more versatile and dwarfing rootstocks). G214 also has resistance to woolly aphid while G11 does not, and G214 is more resistant to fireblight and replant disease as well. Conversely, G11 seems to produce fewer suckers than most apple rootstocks, including G214, but the difference between the two could generally be marginal. It has also been implied a few times that G11 has better anchorage than G214 (as well as most other dwarfing rootstocks), but in either case, staking should probably be permanent.

Budagovsky 9 (Bud 9) is a cold hardy rootstock that is quite resistant to collar rot. Originally, it was thought to be susceptible to fireblight, but it became apparent that it develops resistance with age. Bud 9 does not sucker much, and like the other Budagovsky rootstocks, it is easy to identify, particularly when it is allowed to grow, since it develops red leaves, bark, and cambium (therefore it will not scratch green if you are trying to determine if it is alive or not). Burr knot production is likely more frequent on Bud 9 than on those from the Geneva series, but it is rarely mentioned, so I doubt it is much of an issue. Bud 10, on the other hand, is essentially a larger, more fireblight resistant version of Bud 9 with better anchorage, but it still requires support.

Malling 27 (M27) is an extremely dwarfing rootstock that resists crown rot, suckering, and burr knot formation, but it is quite susceptible to fireblight. The tree needs to be watered regularly when conditions are dry, and the surrounding area should be weeded to prevent competition against its poor root system. It also needs to be carefully trained, more so than those that are more vigorous, during the first few years of growth, but all of these statements are true for the other dwarfing rootstocks as well, just, perhaps, not to the same extent. Weak growing varieties should not be grafted to M27. In fact, you probably shouldn't use this rootstock unless you are experienced, especially since it is quite easy to keep trees on other dwarfing and semi-dwarfing rootstocks within a manageable size.

Related: Apple Varieties