University of Vermont Extension
Department of Plant and Soil Science
Spring, Summer News
Article
GROWING FRUITS IN CONTAINERS
Dr. Leonard Perry, Extension Professor
University of Vermont
If you have poor soil, limited time
or a small space for fruit gardening, limited mobility, or want to garden
creatively or on patios, then you should consider growing fruits in
containers. Half-high blueberries, blackberries,
raspberries, dwarf fruit trees, and even grapes can be grown in
containers. All grow best in full sun,
although brambles will tolerate light shade (with less yield). Keep in mind that blueberries and most fruit
trees need at least two different cultivars, blooming at the same time, for
cross pollination and fruiting.
Perhaps the main challenge to
growing fruit plants in containers in cold northern climates is getting
them to
survive through winter. Plants in the
ground benefit from the stored heat, and if their roots freeze it isn’t
to the
very low levels that roots in pots above ground can experience.
Easiest is to move containers to an unheated
shed or garage that doesn’t get much below freezing during
winter. Rolling supports with casters helps move
large and heavy pots. Another option for
milder climates is to pile soil, compost, or straw around the pots,
combined
perhaps with partially sinking the pots in the ground if they aren’t
too large. In even milder climates, a large wooden tub
insulated on the inside with a solid foam material as used in
construction may
be sufficient.
Minimum pot size is a 5-gallon pail
or pot, but 15- to 20-gallon is better.
Many large containers will work for fruits, ones that are 18 to 24
inches wide and at least 12 to 16 inches deep
being ideal. If deeper, you can add a false bottom or fill
with lightweight material such as wood chips.
I use plastic pots turned upside down.
A large plastic pot is easier to move than clay ones, or consider a
whiskey barrel half or lightweight plastic tub.
Potting soil for containers has very
different physical properties than garden soils, so you don’t want to use
garden soil that also may introduce diseases.
Best is a potting mix of half peat moss and half bagged topsoil or potting
soil. Some mix in weed-free compost as
well. Leave a couple inches on the top
when potting for an organic mulch, or adding a bit of new compost yearly. Plants may need repotting every 3 to 5 years
to keep them vigorous.
Keep plants watered well after
planting, reducing water in late summer each year. Then over winter keep the soil barely
moist. Fertilize with a low analysis
fertilizer such as fish emulsion, weekly the first year and monthly in
subsequent years. Stop fertilizing in
midsummer so plants can harden by winter.
Other low nitrogen fertilizers, as used in gardens, can be used.
Grapes lend themselves to growing on
a trellis or one of the many decorative structures now available such as
obelisks. Although grapes in containers
will be smaller plants with lower yields than if grown in the field, they’re
both attractive and a good choice if not otherwise possible. Grapes, as many plants, will only grow as
large on tops as the roots can support, so fewer roots means smaller tops above
ground. Since these can get heavy,
you’ll need to fasten the trellis or support to the pot sides with wires or
similar.
If the pot becomes top heavy later
in the season with older vines, you may need to anchor it to the ground or hold
it upright with cinder blocks. Unlike
many potted plants, grapes prefer a sandy loam soil. If making your own, a recipe that should work
consists of equal parts (by volume) of good topsoil, peat moss, and
compost. If using up to 20 percent or so
of sand for weight, just make sure the mix drains well.
Grape cultivars (cultivated
varieties) best for containers have their fruit clusters close to
the
trunk rather than at the ends of canes.
Seedless cultivars include Canadice and Interlaken, while seeded
cultivars include Early Muscat, Seyval and Swenson Red (the latter being a
hardy cultivar bred in Minnesota). Sweet
Lace is a cultivar particularly suited for patios and trellises, good as both a
table (eaten fresh) and wine grape.
You’ll need to prune your potted
grapes, the goal being to develop a trunk with several shoots (canes) over the
first couple of years. Prune off all but
four shoots (off the main trunk) the second and future years. Then, during winter, prune these shoots back
leaving “spurs” with two or three buds on each.
These will develop into the next year’s shoots. To help the plants get established in the
first two years, putting their energy into growth and not fruit, you’ll want to
remove all flowers clusters. In the
third and subsequent years, only allow 10 to 15 flower clusters for a 5-gallon
pot (more for larger pots, less for weak or slow-growing plants). Grapes tend to produce many more flowers than
their roots can support, especially if in pots.
Since blueberry bushes can get quite
large, look for the lowbush cultivars that only get one to 2 feet high and are
quite hardy such as the cultivar Tophat.
Slightly taller, and also hardy, are the half-high hybrids such as
Northland (3 to 4 feet tall), North Sky (one to 2 feet), and Patriot (3 to 4
feet).
Be sure and check the pH or acidity of the
growing mix, as blueberries require an acidic soil. They grow best with
a pH of 4.8 to 5.2. Sulfur can be sprinkled lightly on the
surface, or mixed in, to help lower the pH.
An acidic fertilizer, as sold for hollies and azaleas, may be all that
is needed. Make sure and keep roots
moist, as blueberries produce many near the surface that are sensitive
to
drying out. Browning leaf edges may
indicate drought.
Brambles such as raspberries and
blackberries can be grown in containers, but expect less yields
than if grown in the field. The popular
Latham might be a good first choice for the
summer
bearing, with Heritage and the hardy Fall Red for fall bearing. Prune as for those growing in the ground,
perhaps a bit heavier if they get too large for the container. Since many brambles like to spread, you
should divide and repot in spring every couple years to keep plants vigorous. Use only one plant per container, and use a
container wider than deep. If growing near a walk or patio, consider thornless
cultivars such as Canby and Encore.
Dwarf fruit trees are ideal for
containers, the size being determined partly by nursery pruning, sometimes by
the plant genetics, but in large part by the “rootstock” onto which the
desirable cultivar is grafted. Many
popular cultivars are available as dwarfs, just make sure to choose ones best
for your area. Descriptions in specialty
catalogs and local nurseries are a good source of this information.
Prune potted dwarf fruit trees as you would
those growing in the ground. If you have
a narrow space, or want to create a vertical design, try one of the new popular
columnar or pillar apples and peaches. While
the pillar peaches such as Sweet-n-up, Crimson Rocket, and Summerfest have less
spread than their dwarf kin, nevertheless you may need to prune branches back
each spring to about a foot to keep the columnar shape. Northpole is a columnar
apple with fruit similar to McIntosh, Scarlet Sentinel apples are green-yellow
with a red blush, and Golden Sentinel tastes like Golden Delicious apples.
Return to
Perry's Perennial
Pages, Articles 