Selecting healthy plants

There are many books, articles, and websites with tips on selecting healthy nursery plants. The lists usually include checking to be sure your new plant is pest-free, has healthy green leaves, an undamaged stem, and healthy roots. In short, it should look healthy.

Native plants, however, often look different from the common garden center varieties. Not bred for sale, these plants sometimes look – how shall I say it? – puny, in comparison. They do best in the ground. They thrive in our hot, dry climate with tested strategies that were not devised to ensure they can survive neglect and poor care in The Home Depot.

Absolutely perfect! The roots of this Margarita BOP penstemon fill out the pot, without being too dense or tight.

I have popped quite a few plants out of their nursery pots and watched them grow in my own garden and our local nature park. I hope the following list, based on years of looking, growing and learning, will be helpful to those purchasing plants at the upcoming native plant sales.

This California lilac groundcover has thick woody stem, clearly it has been in this pot for a long while.

1. Select properly sized plants. This does not mean select the largest plant in the group. We all like to get the most for our money but an over-sized plant may indicate that it has been in its pot too long. Its roots may be crowded, the plant generally stressed and possibly more prone to transplant shock.

   The smallest plant in the group is either the youngest or it is stunted for other reasons. I actually worry less about it being the youngest, though who wants to pay for a 1-gallon pot when the plant is really a 4 incher in over-sized clothes? Poor growth in plants may be caused by insufficient water, crowding by faster growing neighbors, or genetic weakness. Who knows? The important thing is to pick a plant that is not over- or under-sized for the pot. As I mentioned above, keep in mind that native plants in  nursery pots often look scrawny when compared with The Home Depot specials. Yes, this is subjective, but over time it becomes clearer.

The 1-gallon matilija poppy (right) priced at $13.99 is about the same size as the 3-gallon on the left priced at $34.99. The 3-g may have a more extensive root system, though it is hard to tell. Still, I’d go for the one on the left! (The plant on the right is probably going dormant, not necessarily an indication of ill-health or disease.)

2. Look closely at the leaves. Minor damage is not a big concern. Check to see whether the leaves exhibit browned tips or yellowing. This could indicate an accumulation of salts in the potting medium possibly from over-fertilizing, or some other disease or nutrient imbalance. Some native plants are deciduous, dropping their leaves seasonally or in response to drought, heat or frost, and may look  unhealthy when in fact they are fine (see #7).

   If you see very few older leaves but lots of new, young leaves, it could be that the plant went dry for a period causing it to defoliate. Upon getting more water, it then greened up and leafed out. The consequences of this common problem are varied, depending on what the plant is and how stressed it  was. Similarly, a plant may lose its leaves due to a pest problem. Following treatment with pesticides, the plant may then rebound. Regardless of whether the plant was drought-stressed or diseased, this is an indication that somewhere along the line the plant was stressed and did not get the best care.

Older monkeyflower has woody stem and is sitting low in the pot. Although it may do fine, I would look for a younger plant with stems that are not so woody.

3. Examine the plant’s stem, especially at the collar or crown (the place between stem and roots). Check for damage and breakage.

   Make sure that the collar is not buried. When plants are left in pots too long, potting medium sometimes washes out of the pot, or organic matter in the medium decomposes. The result is that the plant sinks down in the pot. Unscrupulous nursery workers may then just “refurbish” the pot with a scoop of new soil. This is very bad! The collar is buried, susceptible to disease, and the plant was sitting in old, tired soil for way too long. It is not always easy to see whether the collar is buried. Younger plants, like those in 1-gallon containers,  generally do not have very woody stems. If the stem is woody, then you may want to ask the nursery staff to check around the collar for you to make sure it is at the correct height. These plants may also be root-bound (see #4).

4. It is critical to check the root of the matter, but alas, the roots are carefully hidden within the pot. So here is what you do. If the plant looks healthy then lift the pot and check to see whether roots are coming out the bottom. A few tiny root hairs are probably no problem, but avoid plants with larger roots coming out the bottom or cut at the base of the container. Either ask nursery staff for help, or very carefully and gently squeeze the pot to see whether the roots are packed against the pot wall. It would be best to  pop the plant out of its container and thoroughly inspect the roots, but this is frowned upon. Like squeezing fruit at the market, if done clumsily, this can damage good plants. Finally, pick up the pot and give it a good sniff. A sour or unpleasant smell indicates rotting in the root area. If you get one of these, put it down and walk away slowly.

   The significance of crowded roots varies depending on the degree of the problem and the type of plant. Grasses or other plants with fibrous roots usually do fine.

   This wiregrass (Juncus) is severely potbound. I cut the bottom mass of roots off and spread the rest of the roots as best I could. Usually grasses and other plants with fibrous roots do okay, even when potbound. This one, unfortunately, did not survive.

   Plants with woody roots, however, can be very seriously impacted. Trees are of particular concern because the damage to the plant may not be apparent for years to come. When a tree is allowed to remain in its pot too long, its roots will circle the pot. When the plant is transplanted into a larger pot the circling roots are covered. As the roots grow they eventually choke off water and nutrient flow to the plant. Inspect roots of trees carefully before planting. If the circling is not too extreme, they can be pruned and gently straightened.

   This poor tree lived and then died. Who could know that its own roots were choking it to death?

5. Do not bring home someone else’s problems. Check beneath leaves and around the leaf petioles (the leaf stem) for pests. I have brought home plants with mealybugs and not only can they infect your own plants, in my experience, things do not improve. Even with careful washing and dabbing with alcohol, the mealybugs usually win out and I toss the whole mess. Check for aphids and scale on stems and on and under leaves. Slugs and snails may be lurking under mulch or dead leaves on the surface of the potting medium. Also run your finger under the pot and in the drainage holes to check for these slimy pests. You can dislodge the snails and slugs and leave it at that, although some eggs may be left behind. I do not think this is a big problem, especially if you are planting in drier gardens with little organic matter.
6. Pick plants that are in bud rather than in bloom. Most California natives are not in bloom during planting season, though  manzanita, California lilac, wild currant and gooseberry may be. 
   

   Nurseries want to use flowers to facilitate the “impulse” buy. Be wiser, select the plants under the table that are in bud so that you, rather than those in the nursery, get to enjoy the full bloom period.

7. Dormancy is a dirty word for southern Californians. It is as though we believe that it is our right to have plants in our gardens that grow and flower all year long. A long bloom period, though, often requires significant inputs of water, fertilizer, and pesticides. In our mediterranean climate, many native plants shut down – or at least slow down – to withstand the heat and drought. Some are even winter dormant. If you are interested in acquiring a western sycamore or a western redbud, do not let the leafless branches scare you off. Small buds on the branches indicate that it is alive – albeit sleeping.

   One of the first native plants I bought, way back in 2001, was wishbone bush (Mirabilis multiflora var. pubescens). At the 2001 Rancho Santa Ana Botanic Garden fall plant sale, a member of the nursery staff handed me a one-gallon container filled with potting soil. “This is a great plant,” he said. It was high priced for a one-gallon, and as far as I could tell there wasn’t much there. Intrigued, I bought it anyway. When I got home and showed it to my husband I felt like Jack in the Beanstalk, squandering the family fortune for a handful of nothing. Eleven years later, this plant grows each spring, bursts into bloom in June and then dies back to nothing in fall. I bend down, lift the entire plant in one motion and throw it into the compost pile, awaiting the plant’s return the next spring. The moral of the story is, shop at nurseries with knowledgeable staff and high quality merchandise. 

June 2010, wishbone bush is full bloom. Milo provides scale to the picture.