22 
Ol)£ Slower (Brower 
March, 1919 
Hybridizing and Crossing the French Iris. 
(Reprinted by permission from Horticulture. Boston.) By WILLIAM ROLLINS. 
ALL KINDS DO NOT MAKE GOOD FATHERS. 
The pollen of some kinds does not fertilize 
well, yet if these are used as females the 
cross may succeed. If a cross seems desir- 
able do not give up until trying it both ways. 
Perhaps it may not be well to make many of 
these crosses, for oftentimes the resulting 
plants are sterile, ending the line. Emer- 
son said of the Rhodora, “ beauty is its 
own excuse for being.” When the flowers 
of these crosses are lovely they should be 
saved as they can be increased in the usual 
way. I sometimes imagine the flowers last 
longer. 
GROWTH OF THE SEED PODS. 
Here the seed pods are often full grown in 
twenty-four days after pollination. In ninety 
days the seeds are ripe. Do not wait until 
the pods are brown and dry and have opened 
at the top. If you do, some of the seeds will 
be decayed and others eaten by worms. 
Writing of the latter I am reminded to say 
there will often be found on the leaves of 
the Iris in May clusters of yellow eggs, which 
develop into worms that eat the leaves and 
later the seed pods. When the latter are 
forming, go over the rows every day, other- 
wise you will have valuable seed pods ruined, 
like those shown in Figure 10. You must 
search for caterpillars, for they never seem 
to be on the pods in the hours a person is 
in the garden. 
TIME OF PICKING THE SEED PODS. 
As soon as a pod is fully grown and the 
green color faded to a yellow-green, the pod 
being slightly shriveled, pick it. Having the 
seeds what shall be done with them? They 
should be planted immediately. This brings 
us to 
THE SEED BED. 
Make it four feet wide and as long as 
needed. Dig to the depth of six inches and 
save the soil. Dig six inches deeper and re- 
ject the soil. Put in three inches of muck, 
then three inches of dirt, and repeat the 
work until the bed is more than full. 
SIFTING. 
The muck should have been gotten out 
the summer before and mixed with ground 
limestone in the proportion of a ton to a 
cord of muck. First a layer of muck, then 
one of lime until the pile is big enough 
Let it stand over winter to get the acids 
united with the lime. In the spring fork it 
over and sift through netting with a § inch 
mesh. The top soil of the seed bed must be 
sifted through this or a finer sieve. Make it 
six by three feet, of two inch plank. Mount 
on two wooden horses above the trench and 
work soil and muck through with a hoe. 
We know that stones disintegrate into the 
soil and some furnish potash, but there will 
be enough pass through the sieve. The rate 
of disintegration is interesting and will form 
the subject of a future letter. 
FERTILIZER. 
Muck needs potash and phosphoric acid. 
To every thirty feet in length of the bed add 
twelve pounds of the following mixture, as 
soon as the bed is made, working fertilizer, 
dirt and muck together with a spading fork : 
Slag phosphate, 750 pounds ; sulphate of 
potash (the best you can get), 225 pounds; 
permanganate of potash. 25 pounds. If you 
believe in radioactive soil add four ounces 
of oxide of thorium. 
TIME FOR PLANTING IRIS SEED. 
In this climate planting comes the first 
week in September. Plant the seed (which 
should be the color of coffee and milk) one 
inch deep, one inch apart, in rows with only 
room enough to place a foot in weeding, not 
over six inches. As all the work in the 9 eed 
bed must be done by hand, the plants should 
be near together, to make the space for 
weeds small, for labor is very costly. Weeds 
grow faster than the plants. Clover is 
particularly troublesome, for its roots go 
deep before the leaves are large enough to 
grasp. 
WHAT PROPORTION OF SEED WILL PRODUCE 
STRONG PLANTS ? 
This varies greatly with the cross. From 
one of the pods shown in Figure 9 I selected 
133 of the 150 seeds and planted them. 
They produced 77 strong growing plants. 
For this climate that is a good result. Two 
thousand seeds of another sowing the same 
year gave but 107 plants. I have repeatedly 
crossed Macrantha on several of the best tall 
growing kinds. The seed pods were ex- 
ceptionally large, as were the seeds, but the 
germination was very poor, averaging five 
per cent. Another person might get quite 
a different result. I abandoned the use of 
Macrantha, as the erect segments of the 
perianth were too floppy, and considering 
the poor germination the chance of breeding 
this out and yet retaining the large size of 
the flower seemed remote. 
View of a part of an Iris Hybridizing Garden of the size advised in the text, at the time the seed pods were forming. 
