Growing California Native Plants in Containers ~ Tk-123456

Hybrid Monkeyflower thrives on afternoon shade on our porch

Container
growing has many practical advantages.
Containers permit gardening in tiny places – even those with no
accessible earth. Growing plants in containers can be easier for those with
physical or time constraints. Container
gardening allows the gardener to tailor-make the growth medium to the needs of
the plant. It also makes it possible to grow plants with very different water
needs side by side.

Container
gardening also has aesthetic benefits.
Carefully chosen containers increase the beauty of many gardens. A well-placed container can serve as an
accent or focal point; it can also provide attractive aromas or attract
favorite pollinators. Groupings of
container plants can soften a stark wall, entry way or awkward corner. Well-planned containers can even provide a
spot of color for most of the year.

Camas bulbs are lovely in containers

But
the big question for native plant gardeners is: can I grow my native plants in
containers? The answer is an
enthusiastic but qualified yes. We’ve
grown a number of California natives in containers – and learned a few things
along the way. Here are a few tips for
those considering container gardening with native plants.

1.
Start with the easy ones. Some plants are made for containers.
We suggest starting out with the easy ones, then graduating to those that
require more skill, time and patience.
Annual wildflowers, perennials from bulbs and corms, ferns and grasses/grass-like
plants (rushes, sedges, reeds, cattails) are a good place to start.   Next easiest are the herbaceous
perennials.   The most challenging (and
those that require more work) are the larger woody shrubs and small trees.

Plants that require summer water - like these wetland plants

- are easy to grow in containers

2. Plants
that tolerate some (or regular) summer water are easier than those that like to
be dry. In nature, many California native
plants have extensive root systems, allowing them to utilize both shallow and
deep soil moisture. In containers, it’s
easy to over-water plants that normally require no summer irrigation.

Pots of spring-flowering annuals and
native bulbs (which must be summer dry) can be stored in a cool dry place over
summer. Other summer-dry container plants,
including many Dudleyas, can watered sparingly if plants are moved to a shadier
location. But some summer-dry species,
like White Sage, are very difficult to grow in containers in S. California. Avoid trees and shrubs with strict
summer-dry requirements.

3.
Avoid plants with very deep taproots.   These woody plants survive summer drought by
tapping into water reserves deep underground. No container is deep enough to mimic these
natural conditions; such plants are easy to over-water in containers.   Plants with shallower taproots (for example,
perennials like the California poppy) can
be successfully grown in deep pots.

Lilac verbena likes some afternoon shade

4.
Plants that tolerate part-shade or
shade are easier than plants that require full sun. Containers
in full sun – and the planting medium they contain – get hotter than garden
soil. And excess heat stresses plant roots
and can ultimately kill a plant.

There are some work-arounds, if you
need to container garden in full sun. Light
colored pots, larger pots, and those with thick walls remain cooler. Probably the best solution is double-potting (cache-potting).
Be sure that the inner pot (the one which contains the plant) has a diameter
several inches smaller than that of the outer pot. Fill the space between the pots with
vermiculite – or those plastic packing ‘peanuts’ – to insulate the inner pot.

But the easiest solution, in hot
mediterranean climate gardens, is to locate pots in shadier places – or at
least move pots to shadier locations in summer/early fall. Fortunately, many California native plants do
fine in part-shade or filtered sun. These
include many annual wildflowers, perennials from bulbs/corms, herbaceous
perennials, ferns, woodland shrubs and many others.

We suggest you try moving pots to a
slightly shadier location during the hot months. You can always move a plant back to a sunnier
spot if it starts to get leggy.

5.
Choose the right size plant for the
space, usually based on growth rate and mature size. This advice applies universally, but is
particularly important when choosing a native plant for a small area. It’s much easier – and better for the plant –
to choose one that’s the appropriate size.
Fortunately, smaller cultivars of many native favorites are becoming
available. Ask the advice of your native
plant nursery-person. They may be able
to suggest good alternatives

Many natives growing in pots are on display at Rancho

Santa Ana Botanic Garden, Claremont, CA

6.
Choose the appropriate container based
on root characteristics. Both
the size and the shape of the container can be important for growing natives
successfully. Garden ‘bulbs’, annual
wildflowers and some perennials (ferns; succulents; many herbaceous perennials)
have relatively shallow roots, and can be grown in a wide variety of
containers. For S. California, we
suggest choosing containers at least 10-12 inches in diameter and deep; smaller
sizes are too difficult to keep watered in our increasingly dry, windy climate.

Native shrubs and trees – even the
smaller ones – require more care in selecting an appropriate container. Many of them have relatively deep roots, in
addition to the net-like shallow roots.
For them, choose a pot that’s deep enough to allow the roots to
grow. A deeper pot will also allow you
to water more appropriately. You can let
the surface layer dry out between waterings, better mimicking natural
conditions.

Learn as much as you can about a
plant’s root system before choosing a container. Ask your local native plant nursery-person
for advice. They may be able to suggest
specific pots for the plant you’ve chosen.
More container choices – including deep containers – are becoming available
each year.

7.
Tailor the growth mix to plant
requirements. Being able to tailor the growing
medium to a plant’s needs is a major advantage of growing plants in containers. We like to start with a basic potting mix; in
our area, Kellogg’s All Natural Potting Mix or Kellogg’s Native Smart Planting
Mix are good choices. You can then amend
the medium as needed, for your plants particular needs.

To create a quicker draining mix add
perlite; for a moisture-retaining mixture add vermiculite. A sandy mixture can be achieved by adding some
sharp (builders) sand, crushed rock (like decomposed granite) or lava
rock. For an excellent review of soil
amendments see reference 1, below.

A richer, lower-pH soil (appropriate
for forest-floor plants like native Huckleberries) requires the careful
addition of peat moss, pine or redwood bark fines (finely ground pieces) or
humus. We suggest testing the pH of the
potting soil before and after adding ph-lowering amendments, to be sure your
mixture is in the appropriate range.
Test kits or pH paper are readily available in nurseries or where pool
supplies are sold.

Native Wild rose (Rosa californica) likes regular summer

water if grown in a containers

8.
Monitor soil moisture carefully,
particularly in extremely wet and extremely dry conditions. Plants in pots are more vulnerable to both
extremes than plants grown in the ground.
If possible, move pots to a drier
location if plants seem to be ‘drowning’ during periods of excess rain. Keep close watch on your containers during
hot, dry and windy conditions. Even
large pots can dry out in a hurry. We
sometimes water even large pots every other day – even daily – during the
hottest times.

9.
Give container plants a little
fertilizer. The roots of plants grown in the
ground continually reach out to obtain mineral nutrients. Container-bound plants have no such option. Even the least-hungry pot-grown native will
need a little fertilizer sometimes.

Base your fertilizer regimen on the
needs of individual plant species. Those
described as growing in ‘nutrient-poor soils’ won’t need much. Start off with a once yearly dose of ½
strength liquid fertilizer. You can
always fertilize more often, if plants become nutrient deficient.

No need to buy unusual (or expensive) fertilizer
(unless your plant requires a low-pH type).
We like the general purpose, liquid or water-soluble fertilizers; you can
easily mix them with water to create a half-strength solution. Fertilize when
the plant begins to actively grow – often in late winter or spring.

Plants that grow in leaf mulch on the
forest floor, and those from riparian communities, like a richer soil. You may want to try incorporating a
time-released fertilizer into the potting soil each year. We suggest starting with about half the
recommended amount – you can always add more.
Just loosen the top few inches of soil and incorporate the
fertilizer. Alternatively, use the
liquid fertilizer (half strength) several times during the growing season.

Yerba mansa (Anemopsis californica) is a decorative

groundcover that can be grown in a container

10.
Repot or replace container plants as
needed. If you’ve grown plants in containers, you
probably recognize the signs that a plant needs repotting: the roots or plant
are over-filling the pot, flowering decreases and the foliage may look a little
less healthy. You can often carefully lift
a plant out of the pot to check if roots are becoming crowded.

Repotting a native is no different
from repotting other plants. Let the
potting medium dry out a bit to ease removal.
Then carefully remove the plant, divide it (if appropriate) or replant
in a larger container. Plants that can
be divided include native ‘bulbs’, grasses/grass-like perennials and those that
reproduce via rhizomes or root sprouting.
Such perennials are frequently used as groundcover plants, but can also be
grown in containers. For more
information on repotting perennials see ref. 2, below.

For more information on repotting
native ‘bulbs’ see: http://mother-natures-backyard.blogspot.com/2017/02/gardening-with-california-native-bulbs.html

When repotting woody natives into a
larger pot, we suggest upgrading to a pot of at least 6 inches larger
diameter. That way you won’t need to
repot as often. Loosen the soil around the roots, and remove as much old medium
as can be easily removed. Prune off any
roots that encircle the pot, and loosen other roots. Then use fresh potting medium when planting
into the new pot.

If you need to repot a woody plant
back into the same pot, you’ll need to prune/thin the roots. This is done in
the same way for native or non-native species. For more on repotting techniques
see references 3-5, below.

The informal shape of Euphorbia misera works well with

a traditional Mediterranean-style container

11.
Choose container styles that
complement the plants and your architectural/garden style. Containers can provide unique and stylish accents
– or just fade into the background, letting plants play the starring role. Choose
containers that work with your style/design and either complement or highlight
the plants they contain. Consider
foliage, flower color and growth characteristics of the plants when selecting
containers.

Attractive containers are now
available in all price ranges. Or unusual, recycled ‘containers’ may be just
what your garden needs. Think about the role you’d like the containers to play
before you purchase. You’ll likely be living with your choices for
a while.

12.
Choose plants with ‘added value’. When
choosing between plants, select the one that provides food, habitat, medicine,
craft materials and/or scent over one that is simply pretty. Make the most of your limited space; that’s
smart, sustainable gardening at its best!

For more on
growing native plants in containers see:

Planning a Pot: http://www.slideshare.net/cvadheim/container-gardening-2014

Captivating
Containers: http://www.slideshare.net/cvadheim/container-gardens-2015

Native Foods on the
Small Side: http://www.slideshare.net/cvadheim/container-gardens-edibles-2016-final

Beautiful Bowls:
containers for color through the year: http://www.slideshare.net/cvadheim/beautiful-bowls-2017f