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Selecting Nursery Stock |
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Written by Story and photos by Dianne Stortz-Lintz
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Monday, 01 September 2008 |
With fall’s arrival come the autumn sales at the nurseries. If you’re like me, you should never enter a nursery. I consistently think that I’m only going to look, but more often than not I end up spending too much of my disposable income. As a plant professional and a seasoned plant buyer I don’t have too much problem picking out quality transplants from the nurseries or box stores.
I am, however, constantly amazed at what I see people buying. I can tell at a glance that the plants they have selected are going to be less than satisfying for them.
At times I’ve even offered unsolicited advice to plant buyers, but most of the time people are confused by my attempt at being helpful. Now I can be helpful without seeming pushy.
If you just want the highlights of selecting good nursery stock, go to the last paragraph. If you really want to know the “why” of selecting good transplants, read on.
First and foremost, get over what I call the “Big Plant Syndrome.” Big Plant Syndrome is characterized by always buying the biggest plant that either a) you can find in a particular pot size or b) the biggest plant you can afford or c) both. I know I’m causing pain to nursery owners, but you should always buy the smallest plant in a pot or the smallest plant that fits your needs.
Plants that are really big compared to their pots are often pot- (or root-) bound. Pot-bound plants are nursery stock that has been in pots too long. They often have a solid mass of roots and do not do well when transplanted because they don’t have a well-established fine root system to absorb water. Because they are constantly fed water from a hose, they’ve become dependent on a consistent water source to support their luxurious top growth. You should also cut and tease the roots prior to planting, and whenever you disturb roots you increase the time that it takes for the plant to recover.
So if I have to choose between two plants in five-gallon pots, I’ll choose the plant that is less pot-bound—usually the smaller plant. I verify this by removing the plant from the pot. Most nurseries frown on this practice, so you should ask them prior to manhandling a plant, or ask an employee to remove the plant so you can inspect the root ball.
The root ball should slip easily from the pot, and the root mass should be established enough so that the soil doesn’t fall off the root ball. However, there shouldn’t be a solid mass of roots.
Another problem with pot-bound nursery stock is circling roots. Circling roots are a phenomenon usually confined to trees but can occur in shrubs and big rooted perennials.  Circling roots are formed when a tree has been grown too long in a container and occur when the roots grow around the top portion of the root ball where they will eventually strangle or girdle the tree. Sometimes you cannot see a circling root so you’re better off buying stock that is not root-bound.
Buying the biggest plant you can afford that isn’t pot-bound is fine. And again, I’m probably making nursery owners grind their teeth here, but smaller transplants are often more successful and outgrow their larger counterparts. This is because larger transplants require more handling. It is easier to shear the roots from the trunk of a larger transplant. It’s harder to keep them watered and fed until the roots start to establish themselves into the native soil, and it’s harder to dig a big hole.
There are other issues that occur in nursery stock—disease, slug, snail and insect infestations, mechanical damage, nutrient deficiencies and prior evidence of water stress.
The least of these problems is insect infestation. Even though it is relatively easy to rid a plant of insects, you certainly don’t want to pay for a plant infested with bugs. I would recommend that the average homeowner pass the plant by. For the avid green thumb, a plant lightly infested with aphids may represent a cost savings. I often point out the bugs and offer the nursery less to remove the source of infestation by buying it at a lesser price. If they’re not interested, I let them deal with the plant.
Not all plant diseases are created equal. Some diseases are deadly (like sudden oak death) while others (like powdery mildew) are often only a nuisance. But that is only in the field—I will never spend money on a diseased plant if I can help it. Symptoms of diseased plants include powdery looking spots on leaves and stems, wet-looking, discolored or dead spots on leaves and stems, a single dead branch on a tree, curled leaves, wilted leaves or mottled leaves. I could go on listing evidence of disease forever, but in general, if it looks wrong, don’t buy it. There is a caveat to this, some plants have been bred to have mottled, curled and other odd leaves, but you can tell that from the other plants nearby.
Mechanical damage in nursery stock is caused by poor handling and tipping. The plant may be damaged during transport, while it’s moved around in the nursery or more commonly, when it falls over in the wind.
For shrubby and herbaceous plants, damage is often only cosmetic, and we can ask for a discount for buying an ugly plant. For trees, some types of mechanical damage are deal breakers. If a tree has a broken lateral branch, it’s no big deal. However, if the leader or top-most branch is broken, that is a different story. In a species where the leader is vital to upward growth, losing a leader will reduce the appearance. The tree will probably live without a leader, but at best it will be stunted or deformed.
If a lateral branch on a tree has broken off and the bark has torn down the trunk of the tree, pass it by. Likewise, if there is a large wear, cut or tear to the bark on a trunk, do not buy it.
In general you want a tree with a strong straight trunk, with no blemishes and a full healthy crown. The only reason you should take anything less is that you want to take a chance on a discounted tree. However, you won’t see me taking that chance because I don’t like to dig a big hole for a tree that may die or look bad in the long run.
Nutrient deficiencies and water stress go hand in hand. When a plant is in a pot, it is dependent upon its caretaker for all its needs. If a plant has dead or wilted older leaves, it has been drought stressed. If a plant is in a general wilted state, it is either experiencing drought, recently experienced drought and hasn’t recovered, or has been over-watered.
A plant that has experienced drought and has recovered will drop older leaves to compensate for a loss of roots. A plant that is experiencing or has recently experienced drought may not recover, and I would pass it by. But a plant that has been over-watered is not worth buying.
It is difficult to tell the difference between drought-stressed and over-watered plants unless you’re well-trained. In general over-watering goes hand in hand with under-watering. If a plant wilts, that often encourages the caretaker to water the plant more. Because the roots of that plant have been killed due to drought, the plant has no way to absorb the extra water. The water then pools in the soil and rots the remaining roots. This causes it to wilt all the more, which in turn encourages more watering. The only way to tell if a plant is successfully recovering from drought is to pull it from its pot and look for new healthy white roots (dead roots are brown). Often the root ball will smell bad.
Plants with nutrient deficiencies can be pale green, have darker veins or show purple hues. Nutrient deficiencies can be caused by lack of nutrients or over-watering. So again, you may want to pass this plant by depending on your knowledge of plant nutrition.
In general, when selecting nursery stock, use these few rules unless you’re willing to take a chance and the plant is a bargain:
• Select the smallest plant for the pot size.
• Select the smallest plant you need for your landscape design.
• Choose trees with their leading branch and with healthy straight trunks that are clear of wet spots, tears and large lesions.
• Inspect plants for insects, disease, damage, root-boundness and circling roots.
• Choose plants that have vibrant leaves without lesions, are leafy, are not wilted and have good color for their species.
Anything less—pass it by.
Dianne Stortz-Lintz is a horticulturist and greenhouse manager for the City of Reno. For more information, call 224-1680. |
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