Horticulture Report: February 2013


Iris: There are over 200 iris species.  Some grow from rhizomes, most common, others from bulbs.   Irises do best with plenty of sunlight and planted in soil that is fertile and well drained.   Don’t be too generous with fertilizer as it will produce lots of plants and few flowers. Plant iris rhizomes horizontally one foot apart and plant them shallow, just barely cover with soil. When blooms are finished cut faded flowers off to prevent seeds pods from forming, as these pods can weaken the plant.  Deer won’t eat iris, so, many gardeners claim irises have no pest except dogs, cats and children, who can jump on them breaking their stems.   Irises do not need mulching and they do not like overhead watering.

Crocus:  Autumn Crocus (Colchicum autumnale) resembles spring crocuses with white, lavender and rose colored flowers, but they bloom in the fall.  You can plant Autumn Crocuses in early spring. They like light, loamy soil with good drainage. Plant them 3-4 inches deep in a sunny location.  After blooming, let them die back naturally, do not “mow” them down.   The corms should be divided every 3-4 years to stop overcrowding or they will stop flowering. Autumn Crocuses are hardy in zones 5 & 6.

Saffron Crocus (Crocus Sativus) blooms with lavender or white flowers. Sativus’ stigmas (stamens) are the source of saffron, but in case you were thinking of raising them for saffron, it takes thousands of stigmas to produce one ounce of saffron.

Colchicum (Meadow Saffron) and Autumn Crocuses (Colchicum autumnale) are often confused with each other because they are both considered an autumn crocus, and their blooms are very similar. However colchicum is its own genus with at least 15 species, hybrids, and varieties. Colchicums are taller too, growing up to 8” in height and they are more expensive to buy. Be aware that colchicum corms contain a deadly toxic, so wear gloves when working with them.

Autumn Crocus belongs to the Lily family (Liliaceae) along with Lilies, Tulips, and Hyacinths while spring flowering crocuses are a member of the Iris family (Iridaceae) along with Irises and Gladiolus.

Allium:  The Allium, which is Latin for garlic, includes chives leeks, shallots, onions and of course, garlic.  Some members of Allium family are ornamental perennials which produce globe-like flowers. These flowers can be used in arrangements either freshly cut or dried. Plant ornamental Allium bulbs to a depth that’s 2 -3 times the diameter of the bulb, space them 6-12 inches apart. Plant bulbs in full sun and in ordinary soil. It flowers in many different colors and sizes. They don’t ‘have pests.

Gladiolus:  Gladioluses are members of the Iris family, and most of the 200 species are natives to Africa.   Their name comes from “gladius”, which is the Latin name for sword because of their sword-like foliage. Their flowers are borne on spikes 1-5 feet tall.

Plant bulbs in a sunny location 3-8 inches deep, and they look best planted in groups of 6-12 plants of the same color, rather than as an individual plant, or in groups of mixed colors.

Lilium: Lilies are among the most beautiful of the summer blooming flowers.   Historically, lilies were not easy to grow in North America because, unlike other bulbs, lilies never grow dormant. This made it difficult to ship in good condition and often they were infected with viruses. Then Jan de Graaff, who was born in Holland in 1903, became fascinated with Lilies.  In 1928, he started working for the Oregon Bulb Farms, and then in 1924 he bought the company.  After making thousands of lily crosses his flower called Enchantment was instantly success so he began marking lilies successfully.

Lily bulbs deteriorate rapidly, so plant right away. Lilies like very well drained acid soil enriched with enough humus to hold the moisture they need.  Plant bulbs 5-8 inches in a location with full sun until noon then shade in the afternoon. Lilies do well in large deep planters or pots with good drainage.   To discourage diseases water so no moisture stays on the foliage.   Fertilize with fish emulsion or seaweed.    However, the Madonna Lily and the Turks Cap only need their tops 1‘’ below the soil.  . Lilies have a reputation for a short life, therefore the need placing every 3 years.

Dahlias: Few plants offer such a variety of shapes sizes and color and long season of bloom as the Dahlia. It is a member of the daisy family and is a native to Mexico. After the Swedish born botanist Anders Dahl developed several hybrids, the plant was named after him.

Dahlias like rich, deeply tilled, loamy  soil and full sun, but protected from winds .  Do not plant near trees and other plants that will compete with them.   Dahlias over 4 feet tall must be staked because their stems are hollow and brittle.  Insert the stake into the ground before planting so you won’t damage the tuber,  Dahlias like plenty of nourishment and water, so be sure to give it  plenty of compost and manure.

Dahlias that grow over 4 feet tall should be planted 1 foot deep then covered with only 3-4 inches of soil.   After the stem break the surface, add more soil, repeat this until the top of the hole is reach. As it grows pinch off terminal buds to stimulate side branching and encourage a more bushy plant. There are also shorter varieties available now which grow only 2 ½ ft. high. These shorter versions can be grown in a large container.

The ground should be warm before planting Dahlias. To plant, lay tubers horizontally 4-6 inches deep and 18 inches apart, and do not water them after planting.  Give them a low nitrogen fertilizer, but don’t over feed them, and hand weed only.

Dahlias tubers are “thin skinned”, so they are not has cold hardy as a bulb, therefore it’s recommended they be dug up and store for the winter.  However, if you decided to leave them in the ground, cut their stems below the ground level in June. Then in mid-November cover your Dahlia area with plastic to keep the winter rains off of the tubers and add a few inches of leaves, mulch, soil or straw over the plastic to give them extra warmth.   Remove this protected cover in March.

by Mary Anne Wallace